The Pennsylvania State University. The Graduate School. Department of Horticulture. College of Agricultural Sciences

Transcription

1 The Pennsylvania State University The Graduate School Department of Horticulture College of Agricultural Sciences AN EVALUATION OF AN EXTENSIVE GREEN ROOF MAINTENANCE METHOD A Thesis in Horticulture by Richard C. Hoover 2010 Richard C. Hoover Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science May 2010

2 The thesis of Richard C. Hoover was reviewed and approved* by the following: Robert Berghage Associate Professor or Horticulture Thesis Advisor E. Jay Holcomb Professor of Floriculture Robert Shannon Associate Professor of Agricultural Engineering Richard Marini Professor of Horticulture Head of the Department of Horticulture *Signatures are on file in the Graduate School

3 ii ABSTRACT The work presented in this thesis evaluates a green roof maintenance procedure designed specifically to increase the number of plants in genus Sedum growing in sparsely vegetated portions of an extensive green roof. Over their life, green roofs may suffer from poor plant coverage because of factors such as poor initial plant establishment, unfavorable growing conditions, extreme weather, and poor maintenance. Through evapotranspiration, plants contribute significantly to the stormwater and cooling benefits a green roof provides, so maintaining thick plant coverage is important. Plant death also leaves behind areas of exposed growing media which provide weed seeds a place to germinate. Sedum species are desired over other species because of their ability to survive the stresses of living on a green roof thus providing the benefits of evapotranspiration over the entire growing season. The procedure proposed herein seeks to increase the number of Sedum plants with minimal inputs of labor, plant material, and fertilizer, thereby decreasing long term maintenance costs. Through a series of experiments outside on an experimental green roof, and in a climate controlled greenhouse, this thesis demonstrates that Sedum plants on an existing green roof provide a large and viable source of new Sedum cuttings that when dispersed on exposed green roof media will propagate themselves into new Sedum plants. On the experimental green roof, control treatments, where no cuttings were harvested and no cuttings were spread, had significantly fewer new plants per square meter than all treated sections, where cuttings were harvested and spread. A reel mower showed significantly more new plants per square meter than a string trimmer, while both tools required the same amount of time to complete treatment. The greenhouse experiments found no relationship between the rooting of sedum cuttings and irrigation regimes. Three of the four species tested, S. album, S. sexangulare, S. spurium (John Creech) exhibited 100% rooting after 10 days, regardless of whether they were watered daily, every other day, twice in 10 days, or

4 iii watered when they were spread and not watered again. S. kamtschaticum exhibited 100% rooting eventually, but not within the 10 day study period. The greenhouse experiments also found that all the Sedum species on the experimental green roof, S. acre (aureum), S. album, S. kamtschaticum, S. hispanicum, S. rupestre, S. rupestre (Angelina), S. sarmentosum, S. sexangulare, S. spurium (White Form), S. spurium (John Creech), and S. spurium (Fuldaglut), were capable of producing viable cuttings.

5 iv TABLE OF CONTENTS LIST OF FIGURES... vi LIST OF TABLES... vii ACKNOWLEDGEMENTS... viii CHAPTER 1: LITERATURE REVIEW... 1 Chapter 1-1: Types of Green Roofs... 1 Chapter 1-2: Green Roof Benefits... 4 Chapter 1-3: Structural Components Green Roofs... 8 Chapter 1-4: Green Roof Plants Chapter 1-5: Green Roof Planting Methods Chapter 1-6: Vegetation Effects on Green Roof Performance Chapter 1-7: Green Roof Maintenance CHAPTER 2: THESIS GOALS AND OBJECTIVES CHAPTER 3: OUTDOOR EXPERIMENT INTRODUCTION Chapter 3-1: Goals and Objectives Chapter 3-2: Hypotheses CHAPTER 4: OUTDOOR EXPERIMENT MATERIALS AND METHODS Chapter 4-1: Materials...32 Chapter 4-2: Experimental Design Chapter 4-3: Methods CHAPTER 5: OUTDOOR EXPERIMENT RESULTS AND DISSCUSSION Chapter 5-1: Explanation of the Proposed Maintenance Method Chapter 5-2: Efficacy of Treatment Chapter 5-3: Cutting and New Plant Species Compositions Chapter 5-4: Comparison of Harvesting Tools Efficiency Chapter 5-5: Comparison of Harvesting Methods - Cutting Quality Chapter 5-6: Other Observations from the Roof CHAPTER 6 GREENHOUSE EXPERIMENT INTRODUCTION Chapter 6-1: Goals and Objectives Chapter 6-2: Hypotheses CHAPTER 7 GREENHOUSE MATERIALS AND METHODS Chapter 7-1: Materials...66

6 v Chapter 7-2: Methods Growing a Cutting Stock Chapter 7-3: Methods - Watering Regime and Greenhouse Cutting Viability Tests Chapter 7-4: Methods Outdoor Cutting Viability CHAPTER 8: GREENHOUSE EXPERIMENT RESULTS AND DISCUSSION Chapter 8-1: Watering Regime and Greenhouse Cuttings Viability Chapter 8-2: Outdoor Green Roof Cutting Viability Results CHAPTER 9: THESIS CONCLUSIONS WORKS CITED Appendix A A Collection of Vegetation Maps of the Experimental Green Roof Appendix B: A Collection of Vegetation Maps of the Experimental Green Roof from Appendix C: Analysis of Rooflite Green Roof Growing Media Appendix D: Tables and Graphs

7 vi LIST OF FIGURES Figure 1-1: Cut away of a green roof structure... 8 Figure 3-1: Photograph of the experimental green roof on 5/25/ Figure 4-1: Photograph of the short handled hand sheers used in this experiment Figure 4-2: A diagram of the experimental layout Figure 4-3: A map showing the location of the Root Cellar building on the University Park campus of The Pennsylvania State University (The Gould Foundation) Figure 4-4: Graphical representation of the rainfall between 5/1/2009 and 6/7/2009. Cuttings were harvested on 5/28/2009 and 6/1/ Figure 4-5: Daily High and Low Temperatures from 5/1/2009 to 6/30/ Figure 5-1: The mean number of new Sedum plants per square meter for each treatment. The error bars show standard error. Control sections showed significantly lower new plant density than any of the treatments (p = 0.00). The string trimmer showed significantly lower new plant density than the reel mower (p = 0.036). The new plant densities of hand shear and reel mower treatments were not significantly different Figure 5-2: The estimated time required to cut the entire roof (397 m 2 ) Figure 8-1: Rooting data for S. album collected in the greenhouse. Thirty cuttings were sampled Table 8-2: Rooting data for S. sexangulare collected in the greenhouse. Thirty cuttings were sampled Table 8-3: Rooting data for S. kamtschaticum collected in the greenhouse. Twelve cuttings were sampled Table 8-4: Rooting data for S. spurium (John Creech) collected in the greenhouse. Thirty cuttings were sampled

8 vii LIST OF TABLES Table 1-1 Comparison of Extensive, Semi-Intensive, and Intensive Green Roofs. The table is an excerpt from Green Roofs in Sustainable Landscape Design (Cantor 2008)... 3 Table 5-1: Data table showing the mean number of new Sedum plants per square meter for each treatment. Control sections showed significantly lower new plant density than any of the treatments (p = 0.00). The string trimmer showed significantly lower new plant density than the reel mower (p = 0.036). The new plant density of hand shears and reel mower treatments was not significantly different Table 5-2: Comparison of the species composition of cuttings new plants from replications 1 through Table 5-4: Comparison of damaged cuttings taken by each harvesting tool. The percentage of mangled cuttings is significantly different for all three treatments Table 5-5: Comparison of the flowering cuttings taken by each harvesting tool. The reel mower and string trimmer produced significantly more flowering cuttings than hand shears Table 8-1: The percentage and ratio of cuttings from the experimental green roof rooting 7 days after being spread on green roof growing media

9 viii ACKNOWLEDGEMENTS Thank you to the Information Technology Services department at Penn State for funding my graduate studies. Special thanks go to Kathy Mayberry for alerting me of the graduate assistantships at the ITS Help Desk. Thank you also to all the Penn State students, faculty, staff, students, and retirees who had enough computer problems to keep me funded for three years. Special thanks to Ed Snodgrass, John Shepley, and Emory Knoll Farms, Inc. for employing me as a summer intern and for supplying plants for this research project. Thanks to the EKF family for creating the hardest working, friendliest, and most educational work place possible. I ll always keep the tractors rolling slow and low because of Ed. Dr. Rob Berghage, thank you for the freedom to work on this project, and encouraging me to stay the course on the M.S. degree. Thank you Laurel Valley Farms for supplying growing media used in the greenhouse experiments. minute. Thank you to Michele Marini for her statistical advice and willingness to meet at the last

10 1 CHAPTER 1: LITERATURE REVIEW Chapter 1-1: Types of Green Roofs A green roof can be defined simply as any roof that bears vegetation (Cantor, 2008). Vegetation bearing roofs are seen throughout history from sod roofs used by settlers in the American Great Plains in the mid to late 1800 s, in rooftop gardens that appeared in Italian cities in the 1300s and 1500s, and even in 500 to 90 BC in the Hanging Gardens of Babylon (Vidmar, et al. 2007). While they have existed in some form for much of human history, a modern green roof carries with it a twist. Modern green roofs are compound technologies with numerous constructed layers underlying any visible vegetation. Depending on region and the goals of a specific project, green roofs may be referred to as ecoroofs, living roofs, roof gardens, or brown roofs. Their appearance may vary as much as their names imply. Some green roofs are beautiful and elaborate landscape designs like those found on the ground; others may only support low-growing, ground-covering plant species or moss; and some may be brown for significant portions of the year. Despite all the potential variation, there are general definitions that distinguish different kinds of green roofs. The German document Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau, (FLL) (Guidelines for the Planting, Execution, and Upkeep of Green-Roof Sites) defines three categories of rooftop greening: Intensive greening; simple intensive greening; and extensive greening (FLL, 2002). The FLL distinguishes the three categories of rooftop greening by plant selection and maintenance requirements. Intensive and simple intensive greening may have shrubs, grasses, and even trees, though simple intensive greening limits plant selection and

11 2 maintenance requirements comparatively. Extensive greening involves plants that create a virtual nature, and require little external input for maintenance or propagation (FLL, 2002). The three categories of green roofs commonly used in American literature are intensive, semi-intensive, and extensive green roofs. Interestingly, American references distinguish the three categories by the depth of growing media on the roof. Intensive green roofs are characterized by having 30 cm (12 in) or more of growing media. Often the media has higher organic matter content compared to extensive green roof growing media. Extensive green roofs are characterized by shallower media depth, generally less than 15.2 cm (6 in) of largely inorganic growing media (Cantor 2008, Snodgrass 2006). Semi-intensive green roofs fall in between intensive and extensive green roofs in terms of media depth, plant selection, and maintenance requirements. Table 1-1 summarizes the differences between intensive, semiintensive (simple intensive), and extensive green roofs (Berghage, Personal Communication).

12 Table 1-1 Comparison of Extensive, Semi-Intensive, and Intensive Green Roofs. The table is an excerpt from Green Roofs in Sustainable Landscape Design (Cantor 2008). 3 Characteristic Extensive Semi-Intensive Intensive Depth of Growing Media 15.2 cm (6 in) or less +/- 25% of 15.2 cm (6in) 15.2 cm (6 in) or more Accessibility Often inaccessible May be partially accessible Usually accessible Fully Saturated Weight Low kg/m 2 (10-35 lb/ft 2 ) Varies kg/m 2 (35-50 lb/ft 2 ) High kg/m 2 ( lb/ft 2 ) Plant Diversity Low Greater Greatest Cost Low Varies High Maintenance Minimal Varies Generally high

13 4 Chapter 1-2: Green Roof Benefits Vegetating a rooftop replaces an impervious rooftop surface with a pervious one covered with plants, therefore replacing some of the ecological function lost to development. Ecosystem functions, including the evapotranspirative component of the hydrologic cycle provided by predeveloped land, are partially restored. Many green roof benefits are derived from the ability of a green roof to restore part or all of the evapotranspirative component of the hydrologic cycle where development has reduced open space and vegetation (Berghage, et al. 2007). Storm water mitigation, reductions in a building s heating and cooling loads, extended roof life, improved aesthetics, noise filtration, animal habitat, and air filtration are benefits provided by green roofs. The benefits provided by rooftop greening can be valuable to a building s owner, its occupants, and the surrounding community. Some of the most important benefits are discussed in greater detail in the following paragraphs. According to Green Roofs for Healthy Cities, a green roof trade association, up to 75 percent of many cities are covered in impervious surfaces. Roofs in Toronto make up between 15 and 30 percent of the impervious surface of the city. In Portland, Oregon, roofs make up 25 square miles of the city surface (Snodgrass, 2006). When roofs are hard, impervious surfaces, they clearly represent part of the storm water problems in developed areas. After a rain event stormwater can cause combined sewer overflows (CSO) in municipalities with wholly or partially combined sewage and stormwater systems. CSOs discharge untreated or partially treated sewage into nearby waterways (Snodgrass, 2006). From 1997 to 2001, the rate of urban development averaged 890,000 ha/year (2,400 ha/day) (Berghage, et al. 2007).

14 5 Storm Water Mitigation After a rainfall event, green roofs mitigate storm water in three ways: Green roofs increase the time of concentration, retain storm water, and provide some buffering against acid precipitation (Jarrett et. al. 2006, Berghage et. al. 2007). Because of their storm water mitigation benefits, green roofs can reduce the need for other water management features such as retention basins, bioswales, and rain gardens that require additional land to construct. Highly developed areas may not have available land to build other stormwater features, making green roofs an attractive alternative. Research and experience demonstrates that green roofs can retain percent of annual rainfall in northeastern North America, and northern Europe (Berghage, et al. 2007). A green roof with 10 cm (4 in) of growing medium can retain percent of the annual precipitation in the northeastern United States, with nearly 90 percent retention of many summer storms (Berghage et al. 2007). The same study shows that green roofs retain 100 percent of many rainfall events of 15mm (0.6 in) or less. Water retention models developed at The Pennsylvania State University indicate that green roofs will retain 48, 53, 78, 43, and 25 percent of rainfall on the roof in May, June, July, October, and November, respectively in central Pennsylvania (Jarrett, et al, 2006). The study pointed out that one drawback of retaining stormwater on a roof is the stored water is not allowed to infiltrate the soil profile and recharge local supplies (Jarrett, et al. 2006). However, if water is being stored on a green roof in an urbanized area with mostly impermeable surroundings, any water retained on the roof likely can not infiltrate the soil profile anyway.

15 6 In addition to retaining storm water, green roofs improve some aspects of stormwater runoff quality. Runoff from green roofs is clearly and consistently higher ph than runoff from non-greened roofs (Berghage, et al. 2007). Acid buffering is particularly beneficial in places like the Northeastern and Midwestern United States where rainfall ph is well below a ph of 5 and frequently drops below ph of 4.5 (Berghage, et al ) The buffering capacity is due largely to the acid buffering capacity of green roof growing media, but is also influenced by green roof plants. The impact of plants and buffering capacity is discussed in Chapter 1-6. Reduced Cooling Loads The evapotranspirative effects of green roofs reduce the cooling loads for a building and reduce the urban heat island effect. A study at the University of Technology, Berlin Germany, found that daily potential evapotranspiration and real evapotranspiration from a green roof are higher than from the natural landscape. The increased evapotranspiration can be attributed to the urban heat island effect, lower humidity in urban areas, high global radiation, and higher wind speeds on rooftops (Schmidt, 2006).

16 7 Extended Roof Life Vegetation and substrate overlie the waterproofing membrane, thus protecting the waterproofing membrane from solar exposure and ultraviolet degradation. The vegetation and substrate also reduce the large temperature fluctuations common on black roofs where the temperature of the roof can soar well above the ambient air temperature. The combination of these effects causes green roofs to have up to three times the life expectancy of a non greened roof (Vidmar, et al. 2007). Aesthetics Green roofs provide green space in place of hard, often unsightly roofs. Green space is especially beneficial in highly urbanized areas where the rest of the landscape is often concrete, asphalt, brick, and black rooftops. Some green roofs may not be visible to anyone, some may only be seen from a distance, and others may be accessible to a building s owners, tenants, or the public. Regardless of its public visibility, a green roof can provide some of the green space that is lost to development.

17 8 Chapter 1-3: Structural Components Green Roofs Underneath the top layer of vegetation, a green roof is composed of a number of constructed layers, each of which serves an important purpose in the overall performance of the roof. Each layer is briefly discussed below. Some green roof systems may contain more layers than described here, and some roofs may not contain all of the layers discussed. At a minimum, a green roof should consist of a roof deck, a waterproofing membrane, drainage (either a layer or a sloped roof), growing media, and vegetation. Figure 1-1: Cut away of a green roof structure

18 9 Roof Deck The roof deck provides structural support for the green roof. An extensive green roof with 10.2 cm (4 in) or less media weighs between kg/m 2 (10-35 lb/ft 2 ) when fully saturated. Deeper and more complicated intensive roofs weigh between kg/m 2 ( lb/ft 2 ) when fully saturated (Cantor, 2008). The green roof load must be added to snow load, and other live and dead load requirements, so the roof deck and underlying building must be strong and durable to support a green roof installation. Reinforced concrete, precast concrete planks, and steel-concrete composites are most commonly used in green roof projects. Retrofit projects may also encounter plywood or tongue in groove wooden decks (Cantor, 2008). Waterproofing Membrane Ultimately a green roof is a roof, and a roof must keep water out of a building. Therefore, a waterproof membrane is essential to the success of any green roof. It is important to install the waterproofing membrane correctly and detect any leaks before continuing construction of the other layers. Once a green roof is complete, the waterproofing membrane is fully covered by other layers including growing media and plants, thus making leak detection and repair difficult (Snodgrass, 2006). Depending on the underlying roof deck and local building codes, many different waterproofing membranes can be used for a green roof. Common waterproofing membranes include the following materials: thermoplastics, such as polyvinyl chloride (PVC) or thermal polyolefin (TPO); ethylene propylene diene monomer (EPDM) rubber; liquid applied polyurethane (PUR); asphalt; and bitumen (Cantor, 2008).

19 10 Insulation The need for insulation depends on the climate and the goals of the green roof, so insulation is not installed in all green roof projects. If decreasing heat gain or loss is a major performance goal, then insulation may be installed either above or below the waterproofing membrane. Common insulation materials include extruded polystyrene and polyisocyanurate. Commonly, a layer of fiber board is installed on top of the insulation when the insulation overlies the waterproofing membrane (Cantor, 2008). Root Barrier Some kind of root barrier is needed to protect the waterproofing membrane from root penetrations. Sheets of thermoplastics such as PVC and high density polyethylene (HDPE) are commonly used root barriers (Snodgrass, 2006). Copper foil and root-retardant chemicals can be used, but they may be subject to code restrictions. In some cases, the root protection layer is incorporated with other layers, such as the waterproofing membrane itself (Cantor, 2008). If the waterproofing membrane or roof deck is an organic material, such as asphalt or bitumen, an additional root barrier absolutely must be installed above the waterproofing membrane (Snodgrass, 2006).

20 11 Drainage Layer Standing water stresses plants and can lead to leaks in the waterproofing membrane, so removing excess water is important to longevity of a green roof. A sloped roof may provide enough gravity to drain excess water, but flat roofs need some kind of drainage layer to remove gravitational water. The drainage layer can be constructed of highly permeable granular material, such as crushed stone, or of geotextiles or other manufacture sheet materials. Some manufactured drainage sheets consist of cup like structures that can be oriented to retain water, allowing the roof to retain a greater volume of storm water (Cantor, 2008). Once the cups are full, excess water will drain. Additional water retention increases the saturated weight of the roof and should be taken into account during the design process. Filter Fabric A fine filter fabric layer is installed between the drainage layer below and the growing media above. The fine fabric material prevents fine particulate matter from clogging the drainage layer. The filter fabric also acts as a moisture distribution mat, redistributing localized pools of excess water to drier areas of the roof. The filter fabric should be root permeable so plants can access water in the drainage and water retention layers during drought (Snodgrass, 2006). Growing Media Green roof growing media may not resemble rich topsoil much at all. Extensive green roof media must meet several criteria. Guidelines from the FLL dictate physical characteristics of green roof media. The media must be porous; retain water, oxygen, and nutrients; and provide stability for root systems. Though not dictated by FLL guidelines, media may also be engineered

21 12 to be lightweight in order to reduce total green roof load. The ideal extensive green roof substrate should consist of 75 to 90 percent inorganic, weed-free material with some organic material. Commonly used inorganic materials include expanded slate, expanded shale, expanded clay, baked clay, volcanic pumice, scoria, sand, crushed brick, and crushed clay roofing tiles. Compost should be used as the organic matter because soils contain silt and clay that can clog the filter fabric (Snodgrass, 2006). The medium should also strongly resist compaction and deterioration so it retains its depth over the lifetime of the roof. The Pennsylvania State University Agricultural Analytical Testing Laboratory measured the watering holding capacity of 39 multi course green roof media samples using the standard extensive roof media test. The findings showed the average water holding capacity of the media to be 43.1 percent with a low of 14.7 percent and a high of 65.2 percent (Berghage et. al. 2007). Media depth is very important to plant survival. Though extensive green roofs have less than 15.2 cm (6 in) of media, plant viability varies greatly between 5.1 cm and 15.2 cm (2 to 6 in) of inorganic material. A single species of Sedum may survive well in 5.1 cm (2 in) of media, but deeper rooted plants with greater nutrient requirements, such as grasses, will not survive well in such a shallow environment (Snodgrass, 2006). Vegetation The top layer of a green roof consists of vegetation. Requirements for suitable green roof vegetation are discussed further in the Chapter 1-4 Green Roofs Plants.

22 13 Chapter 1-4: Green Roof Plants Given ample water, media depth, and maintenance, the plant palette for green roofs is quite large and can include succulent species, herbaceous species, annuals, perennials, and even shrubs and small trees. However, given the same geographic area, the environment on a green roof, especially extensive green roofs, is more extreme than the environment on the ground. Because a green roof is on top of a building, it is exposed to increased wind velocities, increased sun exposure, increased heat, more frequent drought, and shallower growing media than a similar location on the ground (Durham et. al. 2004) As a result, the plant selection, particularly for extensive green roofs with shallow media and low maintenance requirements, is limited to plants that can withstand the extreme environments on rooftops. Hardy succulent species are well suited to the rigors of life on a green roof. Hardy succulent species in the genus Sedum are commonly used green roof plants. The genus Sedum is a member of the family Crassulaceae of the order Rosales. Other members of the Crassulaceae include Crassula, and Sempervivum. Members of the Crassulaceae store water in fleshy leaves, stems or roots, allowing them to survive drought (Stephenson, 1994). Sedums are highly drought resistant, shallow rooted, and very easy to propagate, all of which suits them to prolonged life on green roofs. The research in this thesis was performed on Sedum species, so while there are many other plant species suitable for green roofs, they are not discussed further in this review.

23 14 Like many drought tolerant species, many Sedums use specialized photosynthesis known as Crassulacean Acidic Metabolism (CAM) (Stephenson, 1994). Plants using CAM photosynthesis open their stomata at night when rates of transpiration are low. Carbon dioxide absorbed through stomata overnight is temporarily stored as the organic acid malic acid. Malic acid accumulates in the vacuoles of leaf cells, increasing their osmotic concentration, which allows the plant to absorb and store water, leading to observed succulence. When temperatures rise the next day and stomata close, malic acid moves from the vacuoles and is broken down to release carbon dioxide within the cells. Using sunlight, CAM plants re-fix the released carbon dioxide into the usual products of photosynthesis, sugar and starch (Ingram, et al. 2002). Non-CAM plants open their stomata during the day when the sun is shining, temperatures are warm, and rates of transpiration high. By keeping stomata closed during the day and open at night, CAM plants reduce the amount of water lost through transpiration. This adaptation allows CAM plants such as Sedum to tolerate large diurnal temperature changes and prolonged drought (Stephenson, 1994). Some Sedum species, such as S. album and S. telphium can switch from C3 to CAM photosynthesis in response to water availability (Nagase and Thuring, 2006).

24 15 Sedum Propagation In addition to their ability to grow in harsh conditions, Sedum species are easy to propagate. In his book Sedum: Cultivated Stone Crops, Ray Stephenson, describes how easily Sedum species can be propagated. For the majority of Sedum species, if pieces were merely ripped off the parent and rammed into any growing medium, some propagations would be successful. To be even more successful, choose healthy, sterile stems (without flowers or buds) and strip them of their lower leaves. When inserted into porous, sandy, or gritty compost, these stems quickly form roots. Avoid keeping cuttings in full sun. Put them in a position where birds, cats, or rodents will not disturb plants and labels. Water the cuttings after a week or so. Unlike mesophytes that relish a watering-in process, Sedum cuttings are likely to rot if watered immediately. By waiting at least three days so that tissue damage has had time to callus, rot is unlikely and small rootlets are likely to have formed to make use of the delayed moisture. Finally, do not take cuttings of biennials or annuals after the longest day of the year. An excerpt from Sedum: Cultivated Stone Crops. (Stephenson, 1994). Stephenson goes on to say that few plants are easier to propagate than Sedums, many of which grow from a single leaf if given proper care. Note that Stephenson specifically mentions that porous, sandy, or gritty compost should be used for successful propagations. As described earlier, green roof media is course and porous, and should contain compost, suggesting green roof media may be well-suited for Sedum propagation. At Emory Knoll Farms, Inc., a nursery specializing in green roof plants, Sedum plugs are propagated almost exclusively from cuttings. Sedum album and S. sexangulare, in particular, root easily from tiny small cuttings. At Emory Knoll Farms, S. album and S. sexangulare cuttings are harvested, then chopped into tiny cuttings and sprinkled onto growing media in a nursery plug. The smaller cuttings are more desirable for these species. (Personal observation of author 2008).

25 16 Chapter 1-5: Green Roof Planting Methods Green roof vegetation is established by five different methods, or sometimes by a combination of methods: direct seeding; cutting propagation; planting nursery plugs; installation of vegetated mats; and installation of vegetated modules. Larger nursery containers should not be used, because the potting medium is rich in organic matter that is unsuitable for green roofs (Snodgrass, 2006). Plants transplanted from containers to green roofs often die when the rich potting media wicks excess moisture away from the roof (personal observation of author). Seeding As of 2006, no green roof in North America has been established solely by planting seeds (Snodgrass, 2006) Seeding may require two to three years before a roof planting is fully established, making seeding the slowest method of plant establishment. Sedum seed is small and difficult to disperse evenly, especially when specific plant designs are specified. One gram of Sedum seed can cover a 929 m 2 (10,000 ft 2 ) roof at recommended 215 seeds per m 2 (20 seeds per ft 2 ). Evenly distributing one gram of seed over 929 m 2 (10,000 ft 2 ) is a daunting task to say the least (Snodgrass, 2006). In the summer of 2008, a mixed Sedum cutting bed was seeded at Emory Knoll farms. The bed required watering three to four times a day in the middle of the hot Maryland summer. This kind of attention makes seeding a rather impractical method of planting a roof.

26 17 Montrusso, et al. (2005) studied establishment rates of Sedum seed on green roof platforms in Michigan. The study shows 100 percent Sedum coverage by the spring of the second year of the study. It is important to note however, that the platforms were irrigated in 15 minute cycles applying 0.38 cm of water with each cycle. Irrigation occurred three times a day from days 1-36, twice a day from days 37-51, and once a day from days 52 to 91, with day 91 being the end of the first growing season. Irrigation resumed once a day during the second growing season, day 362. Cutting Propagation Spreading cuttings directly on the growing media is a viable method of establishing Sedum and Delosperma species on a green roof. Distributing cuttings is the most common planting method in Germany where green roofs are more common (Snodgrass, 2006). Cuttings establish new plants faster than seeds and may not require supplemental irrigation depending on weather conditions and time of year. Cuttings should be spread at a rate of 9-12 kg/100 m 2 (18-25 lb/1000ft 2 ) (Snodgrass, Personal Communication.. 2/2010). Cuttings are more expensive than seeds but cheaper and easier to install than nursery plugs (discussed below). However, there are inherent risks in planting a roof entirely of cuttings. Compared to nursery plugs, cuttings require more monitoring and can require more irrigation to ensure growth. Cuttings can easily be blown or washed off a roof, or moved around by birds and rodents that might be present of a roof (Stephenson, 1994). Using cuttings alone effectively reduces the plant selection to Sedum and Delosperma species (Snodgrass, 2006).

27 18 Nursery Plugs Nursery plugs are essentially small young shoots that are fully rooted in a small amount of propagation media. Plugs are commonly established from cuttings, but can also start from seed. Because plugs have established roots prior to planting in the roof, each individual plug is more likely to survive than an individual cutting. Therefore the risk of total plant failure is reduced as compared to using only cuttings. Planting plugs with established root systems allows the installer to use a greater variety of plant species. Common green roof plugs come in 72 cell plug trays and are 8.9 cm (3.5 in) deep. The typical planting density is 23 plugs per square meter (2 plugs per ft 2 ), which provides full coverage in 12 to 18 months. Doubling the planting density increases the rate of coverage, but also doubles the cost of plant material and may double the labor required to plant the roof. Assuming a planting density of 23 plugs per square meter (4 plugs per ft 2 ), a single 72 plug tray will cover about 3.3 square meters (36 ft 2 ) of roof area. The use of plugs also extends the planting season from just after the last frost of spring until late summer or early fall in mild climates and increases the plant palette to include species other than Sedum and Delosperma (Snodgrass, 2006). Vegetated Mats Vegetated mats consist of a thin layer of mesh in which plants are pre-grown in a nursery or other off-site location. The advantage of a vegetated mat is that the roof is instantly green after installation. Vegetated mats are also useful on sloped roofs because the mat and established root systems help reduce erosion by holding the growing medium in place.

28 19 Vegetated mats have a number of drawbacks compared to other installation methods. Vegetated mats are bulky, heavy, and difficult and expensive to transport. Mats cannot survive long distance transport in hot weather, so refrigerated trucks may be required to move a mat from a nursery to its final location. Once a mat arrives at a job site, it must be unrolled immediately, or else it will die, meaning there is little flexibility to adapt to unforeseen installation problems. Another drawback of vegetated mats is that one square meter of roof space requires one square meter of nursery space to grow the mat, making the mat more expensive to grow per square meter of roof coverage than plugs. When rolled, the weight of all the vegetation is concentrated directly under the mat. This means that, if placed on the roof when rolled, the mat could collapse the roof because the weight of the mat is concentrated. Despite the instant green appearance provided by a vegetated mat, a Swedish study found that after 3 years, there is no difference in succulent cover on roofs planted from cuttings, plugs, or vegetated mats. This means that any of the three planting methods should yield the same level of plant coverage after 3 years. The advantage of a vegetated mat then is only realized in the first two years of life for a green roof installation (Emilsson, 2008). Pre-Vegetated Modules Modules are plastic or metal containers, generally 0.37 to 1.5 m 2 (4 to 16 ft 2 ), which are filled with growing media and plants. The depth of the tray can vary, but should be less than 10 cm (4 in) for extensive green roof applications. Modules are pre-grown at a nursery and placed on top of a roof. Modules are a very expensive installation method, and share many advantages and disadvantage with vegetated mats. Modules contain more growing media than vegetated mats, so they are heavier by area (Snodgrass, 2006). The weight of modules increases their

29 20 associated shipping expenses and makes modules tiresome to move and install manually. However, modules are easy to install without any horticulture knowledge, and can be removed easily should the roof leak or a module die. Like vegetated mats, modules require one square meter of nursery space to one square meter of roof space. Modules can cause weight loading problems if they are stacked during installation or maintenance. Stacking modules concentrates their weight at certain points instead of evenly dispersing the load across the roof. If modules need to be stacked, the stacks should be kept small. Chapter 1-6: Vegetation Effects on Green Roof Performance A green roof must support 60 percent plant coverage before it is considered a finished product that can be handed over from a contractor to a building owner (FLL, 2002). In addition to the aesthetic value provided by plant coverage, plants have significant impacts on the ability of a roof to provide all the benefits mentioned in Chapter 1-2. Roots hold the growing media in place preventing erosion, affect heat loss from a building, and affect the stormwater retention abilities of the roof. Keeping desirable plant coverage maintains the intended benefits for the life of a green roof. During establishment, rapid root growth helps prevent wind and water erosion by holding the growing media in place on the roof (Rowe, et. al., 2006). Should all the growing media be lost to erosion, the green roof would no longer support plant life and no longer be considered a green roof.

30 21 Transpiration affects heat loss from a building, thereby affecting the cooling load for the supporting building. Two types of heat loss are considered: latent heat loss and sensible heat loss. Latent heat loss is heat lost due to evapotranspiration. Sensible heat loss is heat lost due to convection and conduction. The latent heat loss is three to eight times higher than the sensible heat loss from a green roof. There is no doubt that plant transpiration is partly responsible for the latent heat loss from a green roof (Gaffin et al. 2006). Without a healthy plant population, a green roof can not realize all its potential energy saving benefits. It has been suggested that the stormwater retention benefits of a green roof are due to the water holding capacity of the green roof growing medium with little contribution from plants. However, experiments at The Pennsylvania State University using green roof modules planted with succulent Delosperma nubigenum, Sedum spurium, and Sedum sexangulare suggest that plants can contribute as much as 40 percent of the annual stormwater retention function of a green roof (Berghage, et al. 2007). The contribution of plants to water retention appears to be due to the effects of evapotranspiration on media water storage. Plants use water for growth, metabolism, and cooling. To fulfill these life requirements, plants must use their roots to remove water from the growing media, move it through vascular tissue, and release it through pores called stomates. By removing water from the growing medium, plants replenish the water storage capacity of the medium. Using lysimeters and vegetated and non-vegetated green roof modules, Berghage, et al. (2007) found that vegetated modules experienced more rapid water loss for the first 5 to 6 days following irrigation than nonvegetated modules. After 5-6 days, the rate of water loss slows and is not statistically different than the rate of water loss from unplanted modules.

31 22 Through the use of modeling, studies at The Pennsylvania State University suggest that increasing media depth provides surprisingly little increase in the annual storm water retention of a green roof. The model suggests that a green roof with 89 mm of growing media, planted with Sedum spurium, providing 40 mm of water retention capacity will retain 45 to 55 percent of annual rainfall volume in State College, Pennsylvania. In the same climate, providing only 3 mm will retain 25 to 40 percent of annual rainfall (Jarrettt, et al. 2006). The model uses a low storage capacity of 3 mm and high of 76 mm. The percent of annual rain retained varies from about 35 to 55 percent respectively. This suggests two things: first, that increasing the thickness of growing medium does not greatly impact the annual rain water storage capacity of a roof, second, that adding as little as 3mm of water storage capacity to a roof significantly reduces the annual rainwater runoff from that roof. A roof with 3mm of storage capacity does not provide enough media depth to support plant life, so such a roof in not considered a green roof (Jarrett, et al. 2006). Selecting plants with large leaf area, high concentration of stomates, and high water demands will increase the evapotranspirative potential of a green roof, which may increase the economic benefits of green roofs. By increasing economic benefits green roofs may be more attractive to building owners and communities (Compton, et. al. 2006). In order to increase economic benefits, Compton and Whitlow argue that green roofs should be designed with the goal of optimizing evapotranspirative benefits, rather than the goal of reducing maintenance. By not allowing rain water to drain, using plants with high rates of evapotranspiration, and irrigating, the authors created a zero stormwater discharge green roof system. Theoretically a roof populated with plants that have large leaf area and high densities of stomata will use more water for evapotranspiration compared to a roof populated with low

32 23 growing, succulent species with high tissue to volume ratios. However, irrigation is required to grow the former, while the latter will survive periods of drought. A green roof only reaps the benefits of evapotranspiration when the plants are alive, so low growing succulents seem to be a better choice on non-irrigated roofs (Berghage, et al. 2007). In a study testing the acid rain buffering capacity of green roof media, Berghage et. al (2007) found that plants generally have impact the buffering capacity of a green roof. The study used planted and unplanted green roof modules irrigated with deionized water adjusted with sulfuric acid to ph 4. Leachate from planted modules was as much as 1 ph unit higher than the leachate of unplanted modules. Eight of the nine plant species tested produced higher ph leachate than leachate from unplanted modules. The ph difference between planted and unplanted modules became more pronounced after about 50 to 100 days of the study. Chapter 1-7: Green Roof Maintenance The focus of this thesis is finding a suitable method of increasing Sedum coverage on a green roof suffering from poor plant coverage. Ultimately this is a maintenance concern. Maintenance during establishment is critical to the long term success of the roof, and hand weeding and fertilization are required (Snodgrass, 2006). The FLL (2002) dictates plant cover requirements be met before a green roof is handed over from the contractor to the owner. Seeded or planted vegetation should have gone through a dormant phase, and where weather permits, a period of drought or frost, generally this requires 12 to 15 months. Green roofs created

33 24 by seeding and planting of shoots of the genus Sedum should provide as uniform a plant stock as possible and aim to provide 60 percent ground cover when the plants are in an uncut state. At least 60 percent of the plant stock must consist of varieties contained in the seed mixture. The population of shoots from plants in the genus Sedum must be no less than 75 percent of plant stock and those shoots must have taken root. Fostered and alien vegetation can not be considered part of the 60 percent ground cover. If plants in the fostered and alien category exceed 20 percent of the ground cover, the site is deemed unsuitable for handover. Vegetation which has become rampant and thus weakened by excessive watering and fertilization is not fit to be handed over. The FLL (2002) instructs that the maturation period of a roof, the time between planting and roughly 90 percent plant coverage, can take up to two years on extensive green roofs, depending on the planting method and how far development has advanced. After maturation, additional maintenance work is needed to maintain high percentages of plant coverage. Plant care that should continue after the maturation period includes feeding with nutrients, removal of alien coppice material and other unwanted vegetation, pruning and thinning, and infill seeding on sizeable bare patches (FLL, 2002). The FLL dictates that as a rule, maintenance on extensive green roofs consists of nothing more than one or two inspections per year. The initial growing media should contain enough fertility to support the roof for a year. After a year, slow release fertilizer should be applied at a rate of 5 gn/m 2 on extensive roofs and 8 gn/m 2 on intensive green roofs (FLL, 2002) slow release fertilizers are commonly used (Snodgrass, 2006). After 5 or 6 years, fertilization may not be needed at all, depending on the health of the initial planting (Snodgrass, 2006). Fertilization should provide enough fertility to support hardy succulent species, but not enough to promote weed growth. Over fertilization

34 leads to increases in weed coverage without increasing the coverage of desirable species such as Sedums. 25 Fertilization alone could potentially increase the desired plant coverage on a green roof, and it might be a welcome addition to the method described here. The addition of fertilizer will increase materials and labor costs associated with any maintenance procedure. As noted in the literature review, the rate of fertilization should provide enough nutrition to sustain Sedum species, but not so much as to encourage weed populations. This balance may be difficult to attain as there is a fine line between appropriate fertilization and excessive fertilization. Fertilization also has the negative side effect of adding nutrients to any runoff that is discharged from the roof. Because storm water mitigation is a primary goal of green roofs, adding nutrients to the runoff is not desirable. Aside from aesthetics, thick coverage by desired plant species is important for reducing other maintenance requirements. Fully vegetated roofs are far more resistant to weed pressures. Some weeds are inevitable in a green roof, because weed seeds are introduced in the growing media, by wind, birds, rodents, and humans. When allowed to grow, weeds can out-compete desired plants for nutrients and water during periods of optimal growing conditions then die during periods of drought and stress leaving large empty patches of exposed media. The exposed media then provides an excellent place for a new generation of weed seeds to germinate. Exposed media and dead plants are also unsightly. Weeding should occur before the weeds are allowed to set seed (Snodgrass, 2006).

35 26 To maintain the acid buffering capabilities of the roof system, Berghage, et al. (2007) estimate that media ph should be evaluated every 13 and 19 years for clay-based and slate-based media respectively. The study assumes no acidification of the media except that from acid rain deposition. At that point, liming may be required to replenish the ph buffering capacity of the media. Maintenance unrelated to plants must occur over the life of a green roof. The FLL (2002) states that maintenance work should include ensuring that roof outlets and drainage and watering systems are in working order; removing dirt and deposits from inspection manholes, overhead sprinklers, roof outlets, and drains; ensuring that surrounding fastenings and other structural components are firmly in place and in good condition; and removing gravel deposits at joints and on equipment should be conducted at intervals of several years.

36 27 CHAPTER 2: THESIS GOALS AND OBJECTIVES This thesis proposed and evaluated a method of landscape maintenance designed specifically to increase plant coverage on poorly vegetated portions of a green roof. Sedum plants already established on the roof provided thousands of cuttings, which in turn provided numerous propagules. Sedum cuttings were harvested manually from plants established on the experimental roof using four tools: two pairs of hand shears, a manual reel mower, and a gasoline powered string trimmer. Two pairs of hand shears, a pair with an extension pole and a pair without an extension pole, were used because the pair with the extension pole proved too slow and tiresome to continue using. Cuttings were then spread by hand on exposed media, watered immediately, and allowed to root and grow for the remainder of the growing season. Two experiments were used to evaluate the proposed method: The first experiment was performed outside on an experimental green roof from May to October, 2009 at the University Park campus of The Pennsylvania State University. The second experiment was conducted in a greenhouse from April to October 2009 at the same institution. The first objective of the thesis was to demonstrate that the proposed maintenance method can be used to successfully increase the number of new Sedum plants on the green roof by the end of one growing season. The second objective of the thesis was the evaluation of four different tools for their usefulness for harvesting Sedum cuttings from a green roof. The third objective was developing a watering regimen to reduce Sedum cutting death and improve rooting. The fourth objective was to show that all the Sedum species present on the green roof were

37 28 capable of producing viable cuttings. By meeting these objectives, the proposed maintenance method can be honed to supply effective and efficient Sedum coverage.

38 29 CHAPTER 3: OUTDOOR EXPERIMENT INTRODUCTION Research suggests that full plant coverage is necessary to reap all the potential benefits of a green roof. Realistically, not all green roofs will attain and maintain 100 percent plant coverage. Poor plant establishment, poor plant choices, poor maintenance, poor growing conditions, and extreme weather conditions can all lead to less than 100 percent coverage. Figure 3-1 shows the green roof on which this experiment takes place before any treatments were applied. Figure 3-1: Photograph of the experimental green roof on 5/25/2009. This photograph shows noticeable areas of exposed media between patches of establish Sedum plants. Like other green roofs, poor plant coverage resulted from a combination of poor plant establishment, poor plant selection, and little maintenance.

39 30 Chapter 3-1: Goals and Objectives The goal of this experiment was the evaluation of a green roof maintenance method introduced in Chapter 2 as a commercially viable method of increasing Sedum coverage on a green roof. The first objective of the experiment was showing that harvesting stem and leaf cuttings and then spreading them on exposed media lead to the establishment of new Sedum plants. This objective was met by determining and comparing the density of new Sedum plants in treated and untreated areas of the roof at the end of the growing season. The second objective of the study was evaluating four tools for efficiency in harvesting Sedum cuttings. The four different tools used in the study include two different types of hand shears, a manual reel mower, and a gasoline powered string trimmer. One pair of hand shears had an extension pole and the other did not. Other tools may be suitable for harvesting cuttings, but only four were tested in this experiment. The objective was met by timing how long it took the author to harvest cuttings from one treatment and by comparing the quality of the cuttings produced. Quality was measured by general appearance and health and by whether the cutting was flowering. The third objective was a comparison the species composition of the cuttings harvested at the beginning of the season to the new plants counted at the end of the season. This objective was

40 met by noting the species of each cutting in a random sample of cuttings and noting the species of each new plant counted. 31 Chapter 3-2: Hypotheses For the purpose of these hypotheses, the act of harvesting and spreading cuttings was considered a treatment. Therefore a treated section was one in which cuttings were harvested with any tool and spread by hand. Control sections were those in which no cuttings were harvested and no cuttings were dispersed. The specific hypotheses evaluated in this study were the following: experiment. 1) Treated sections would show greater densities of new plants at the end of the 2) There was a relationship between the composition of the cuttings harvested and the composition of the new plants on the roof. 3) One of the four harvesting tools would yield higher quality cuttings than the others. Criteria for evaluating cuttings are described in this report. 4) One of the harvesting tools would be more efficient than the others. Efficiency was measured as time required to take cuttings from one treatment.

41 32 CHAPTER 4: OUTDOOR EXPERIMENT MATERIALS AND METHODS Chapter 4-1: Materials Harvesting Tools Two sets of hand shears were used in this experiment. The Hound Dog long handled, hand actuated grass clippers were used to harvest cuttings in replications 1, 2, and 3. The Hound Dog is a product of Ames True Temper, Camp Hill, PA The Hound Dog shears were purchased inexpensively at Ollie s Bargain Outlet of State College, Pennsylvania in May 2009, and the product appeared to be discontinued by the writing of this thesis ( The long handled shears were used in an attempt to reduce worker fatigue caused by bending over for an extended period of time, but this device was very slow, cumbersome, and tiresome to use. In replications 4, 5, and 6 standard short handled shears were substituted for the Hound Dog. The standard shears did not have a company name, but a photograph can be seen in Figure 4-1. The short handled sheers were comparatively more maneuverable, faster, and less tiresome to use than the Hound Dog, but they did require the worker to bend over while harvesting cuttings.

42 33 Figure 4-1 Photograph of the short handled hand sheers used in this experiment. The manual reel mower was an unknown brand in old, but working condition. The blades were capable of cutting long grass, but it was not sharpened prior to use on the green roof. The mower was capable of cutting all the Sedum species living on the roof. The mower was also capable of cutting weeds present on the roof as long as the plant material was taller than 3.8 cm (1.5 in). The string trimmer used in this experiment was a Troy-Bilt model TB10CS powered by a two cycle gasoline motor. The string trimmer was produced by MTD Products, Inc. Cleveland, Ohio.

43 34 A wet dry vacuum was used to collect cuttings. The vacuum was a Shop Vac model 90P650A powered by 6.5 horsepower electric motor (120V 60 Hz 12 A). The vacuum was manufactured by the Shop Vac Corporation, Williamsport, Pennsylvania. Plant Material The only plants used in this experiment were ones already established on the experimental green roof. During the experiment, no plants were imported from an outside source. The plants of interest were all Sedum species and included Sedum acre aureum, S. album, S. rupestre Angelina, S. hispanicum, S. kamtschaticum, S. rupestre, S. sarmentosum, S. sexangulare, S. spurium (John Creech), and S. spurium fuldaglut. All these species produced viable cuttings and new plants.

44 35 Chapter 4-2: Experimental Design The experiment was conducted using a randomized block design. There were four treatments in the experiment, and each treatment was used one time within a replication. The experiment was replicated five times. The four treatments were as follows: Treatment 1: Control. No cuttings were harvested and no cuttings were spread Treatment 2: Cuttings were harvested with hand shears. Two types of shears were used because the first pair was too inefficient to continue using. The shears were grouped together into one treatment. Harvested cuttings were spread by hand. Treatment 3: Cuttings were harvested with a manual reel mower. Harvested cuttings were spread by hand. Treatment 4: Cuttings were harvested with a gasoline powered string trimmer. Harvested cuttings were spread by hand.

45 36 Roof Area = 397 m 2 (4273ft 2 ) Eisenhower Auditorium 4 - Reel Mow er 4 - String Trimmer 3 - String Trimmer 3 - Control 4 - Hand Sheers 4 - Control 3 - Hand Sheers 3 - Reel Mow er 7.11 m (23' 4") 5 - Control 5 - String Trimmer 2 - Control 2 - String Trimmer 5 - Reel Mow er 5 - Hand Sheers 2 - Reel Mow er 2 - Hand Sheers 6.93 m (22' 9") 6 - Control 6 - Hand Sheers 1 - String Trimmer 1 - Reel Mow er 6 - String Trimmer 6 - Reel Mow er 1 - Hand Sheers 1 - Control 6.81 m (22' 4") North 9.55 m (31'4") 9.47m (31' 1") Greenhouses Tyson Building Figure 4-2: A diagram of the experimental layout. The roof was already divided into six sections by cinder blocks that were part of the roof installation. Each of the six sections served as one full replication of the experiment. Cinder block divisions are represented by dotted lines. The replications are labeled 1 through 6 in a counter clockwise fashion with replication 1 being the northwest corner of the roof. Each section was divided into quarters with a grid of masonry twine. Masonry twine divisions are represented by thin solid lines in Figure 4-2. Each treatment area was labeled with its section number and the treatment it received (Section Number Treatment), i.e. 1 Control.

46 37 The six sections were not equally sized, so therefore the replications and the treatment areas were not the same size. The size of each replication and each treatment area is found in Appendix D: Figures and Tables. Physical Characteristics of the Experimental Green Roof Figure 4-3: A map showing the location of the Root Cellar building on the University Park campus of The Pennsylvania State University (The Gould Foundation). The experimental green roof was installed in 2006 and planted as a class project by the 2006 green roof class taught Dr. Robert Berghage at The Pennsylvania State University. The roof was intended as a research roof. Because the root cellar building was mostly underground, the

47 38 roof was actually at the ground level, and it was viewable by the public. The root cellar building was not heated. Sections 1 and 6 were installed with media 15 cm (6 in) deep. Sections 2 through 5 were installed with 10 cm (4 in) deep. In all sections, media was mounded to a depth of about 20 cm (8 in) along the lines of cinder blocks. Mounding provided enough media depth for the growth of some herbaceous species along the edges of the individual sections. Weight loading was not an issue for this roof because the underlying building was constructed of thick concrete capable of withstanding significant live and dead loads. Because weight loading was not an issue, the media on this green roof was not comprised of lightweight inorganic aggregate material common on commercial roofs. In an effort to reduce the total cost of installation, inexpensive but heavy materials were used for growing media. The media used was a custom mixture of roughly 75 percent sandstone gravel and 25 percent pre-consumer compost from the composting facility at The Pennsylvania State University (Berghage, 2010 Personal Communication.). Some of the original experiments on this roof tested plants for their survival on green roofs. Many of the original plant species did not survive on the green roof in this climate. Additionally, the roof was planted with distinct patterns of vegetation. The death of experimental plants and the heavy patterns took their toll on the total plant coverage, leaving large areas of exposed media with no plant coverage. Although many herbaceous plants died, most Sedum species thrived, establishing areas of Sedum coverage. Vegetation maps from 2007 and 2009 are included in Appendix A.

48 39 Cutting Data A sample of 1500 cuttings was used to characterize the cuttings that were harvested and spread during treatment. Cuttings were evaluated by species, quality, and length. Cutting weight was not measured because rain fell prior to harvesting the cuttings. The water weight would have significantly affected the total weight of any cutting sample. Species The species of each cutting was noted. If a cutting was unrecognizable, it was scored as other. The data were used to determine species composition. Composition was reported as the percentage of the total cuttings represented by a single species. For example, to find the percent of S. album, the number of S. album cuttings was divided by the total number of cuttings. The ratio was multiplied by 100 to yield a percentage. Quality Quality was partially subjective and scored as either yes or no based on two criteria: flowering and damage. The quality of cuttings was used to evaluate harvesting tools. Flowering: Flowering was scored yes if a cutting had buds or flowers. Damage: Damage was scored yes if a cutting was broken, ripped, or otherwise severely damaged by harvesting. Damage was subjective. A cutting marked as damaged was one that the author would likely throw away if he were trying to achieve 100 percent successful propagations.

49 40 Length Cutting length was measured in inches and rounded up to the nearest half inch. The average cutting length was used as the standard cutting length for greenhouse experiment explained in the greenhouse experiment section of this thesis. New Plant Data The only areas of the roof surveyed were those where exposed media comprised more than 75 percent of a 1 square foot survey area. Areas with established plants were not surveyed. New Plant Density (NPD) NPD was a count of new plants per square meter of exposed media. Values were collected by counting all new plants (NP) in a 1 square foot survey plot. Multiple survey plots were used in each treatment. To outline the survey area, a 1 foot by 1 foot frame constructed of PVC pipe was laid on an area of exposed media. Data were converted from NP/ft 2 to NP/m 2. New Plant Species The species of each new plant was noted. The data were used to determine the species composition of the new plants. Composition was reported as the percentage of the total new plants represented by a single species. For example, to find the percent of S. album, the number of new S. album plants was divided by the total number of new plants. The ratio was multiplied by 100 to yield a percentage.

50 41 Other Data Time of Harvest (Efficiency) The time required to harvest cuttings from each treatment is measured. Efficiency was used as criteria to evaluate harvesting tools. Vegetation Maps Vegetation maps of each section were drawn prior to any treatments. The vegetation maps for 2009 are found in Appendix A. Experimental Timeline Cuttings were harvested on two dates: 28 May, 2009 and 1 June, The experiment concluded on 28 October, The time of year when cuttings were harvested was important to the survival of new plants. Late spring or early summer seemed to be the best time to harvest cuttings. In a personal conversation, Ed Snodgrass, author of Green Roof Plants: A Resource and Planting Guide and owner of Emory Knoll Farms Inc., noted that Sedum cuttings were more viable before they flower. He noted that some German companies prune their stock beds all summer so they never flower, thus providing viable cuttings all season. Most of the Sedum species on the experimental roof flowered in summer or fall, not in the spring. In this experiment cuttings were spread immediately following harvest. There was the added concern that spreading cuttings in the middle of summer with high temperatures and sun exposure would kill cuttings before they had a chance to root.

51 42 Other evidence suggested that spring was the best time to plant green roofs in order to have the maximum survival rate over the first winter. A study at the Michigan State University found that 81% of plants survived when planted in the spring, while just 23% survived when planted in the fall (Getter, et. al., 2007). All this information suggested that an existing roof should see the best results when cuttings were harvested and spread in the late spring or early summer. Finally, in his book Sedum: Cultivated Stone Crop, Ray Stephenson suggested not taking cuttings of annuals or biennials after the summer solstice, which was the longest day of the year. The summer solstice fell on 21 June, 2009 (Earth s Seasons,

52 43 Chapter 4-3: Methods The experiment consisted of four separate procedures carried out in order: Drawing a vegetation map; harvesting cuttings; collecting cuttings; and spreading cuttings. The vegetation map was drawn prior to any roof treatments and showed the location and species of established plants as well as the location and relative size of areas without vegetation. Data were collected during cutting harvest, after cutting collection, and at the conclusion of the experiment in October. Each step is described in more detail below. Drawing a Vegetation Map Blunt wooden stakes (so not to pierce the waterproof membrane) and masonry twine were used to create a grid of 0.91m by 0.91m (3ft by 3ft) squares across the entire roof. The maps were drawn between 18 May, 2009 and 22 May, The intersection of the north-south line of cinder blocks and the line of cinder blocks on the north side of each replication (the side toward the greenhouses) was used as the origin for each grid. After the grid was created, a vegetation map of each individual square was drawn. The edges of the vegetation patches were drawn, and the species in each patch were labeled. Colored pencils were used to color the map according to the color key included with the maps in Appendix A. Drawing each square individually enhanced the detail and accuracy of the map because it allowed the author to better estimate the size and orientation of individual patches of vegetation. The control treatments were noted with CONTROL written in purple colored pencil.

53 44 Harvesting Cuttings Cuttings from replications 1, 2, and 3 were harvested on 28 May, Cuttings from sections 4, 5, and 6 were harvested on 1 June, The dates were chosen because they fall after the last day of frost and before the summer solstice. Two dates were used because there was not time to complete all 6 replications in one day. Beginning in Section 1 and proceeding counterclockwise, all four treatments were applied in one section before treatment began on the next section. In other words, each entire replication of the experiment was completed before the next replication began. At the time of cutting collection, many of the plants were budding or flowering. Although it was nearly impossible to completely avoid harvesting cuttings from flowering plants, cuttings were harvested preferentially from plants that were not flowering, and an attempt was made to avoid flowering plants. The experimental layout in Figure 4-2 was used to locate each treatment. The individual steps of the treatment are described in greater detail below. Data Collected - Time Time was measured while cuttings were being harvested. The time data from replications 1, 2, and 3 were collected on 28 May, 2009, and the time data from replications 4, 5, and 6 were collected on 1 June, A stop watch was used to measure the time required to harvest cuttings from each treatment area. For each section, the section number and the tool used were noted. The sizes of the treatment areas varied slightly. The correct area of each treatment is found in Appendix D:

54 Figures and Tables. Using the measured time and area of each treatment, the efficiency of each tool was calculated as the time required to harvest cuttings per square meter of roof area. 45 Treatments Treatment 1: Control No cuttings were collected or spread. Treatment 2: Hand Shears Existing Sedum plants were cut approximately 3.8 cm (1.5 in) above the surface of the growing media with hand shears. Cuttings from flowering parts were avoided, and foliage was not completely removed from any individual plant. The cuttings were allowed to fall onto the surface of the roof without any additional distribution. The Hound Dog long handled grass clippers were used in replications (sections) 1, 2, and 3. The regular garden shears were used in replications (sections) 4, 5, and 6. Treatment 3: Reel Mower The blades of the reel mower were set approximately 3.8 cm (1.5 in) above the surface of the roof. If the experiment were repeated, blade height would need to be adjusted based on how easily the mower can be pushed. In some instances, multiple passes over the same patch of vegetation were necessary to harvest all the potential cuttings. Repeated passes were made at different angles, approximately 45 degrees from the original angle of attack. Cuttings from flowering parts were avoided, and all foliage was not removed from any individual plant. The cuttings were allowed to fall onto the surface of the roof without any additional distribution.

55 46 Treatment 4: String Trimmer Existing plants were cut about 3.8 cm (1.5 in) above the surface of the roof. Cuttings from flowering parts were avoided and all foliage was not removed from any individual plant. The cuttings were allowed to fall onto the surface of the roof without any additional distribution, although the string trimmer did throw cuttings a few feet at times. The direction in which the cuttings were thrown could be controlled by the angle at which the trimmer contacts a plant. When harvesting the edge areas of string trimmer treatments, the trimmer was angled so it threw cuttings back into the treatment area and away from other treatments. Collecting Cuttings Cuttings were collected from each treatment using a 6.5 horse power 16 gallon Shop Vac brand wet and dry vacuum, one treatment at a time. An attempt was made to collect all the cuttings in the treatment area. Once all the cuttings were collected in a single treatment, the cuttings were thoroughly mixed by reaching into the Shop Vac and stirring them by hand. A random sample of cuttings (two or three large handfuls) was removed and placed into a brown paper lunch bag. One full bag of cuttings was collected from each treatment for a total of twentyfour bags full of cuttings. The remainder of the cuttings, which was the majority of the cuttings, was spread immediately as described below.

56 47 Spreading Cuttings Except for the cuttings that were sampled for data collection, all the cuttings collected in the Shop Vac were immediately dispersed in the treatment area from which they were harvested. The cuttings were spread by throwing them onto exposed media until all the collected cuttings were dispersed. An attempt was made to evenly cover the bare patches and to avoid throwing cuttings on existing plants. Data Collected Cutting Quality Cutting data was collected immediately after cutting harvest. One hundred (100) random cuttings were removed from each bag of cuttings. The following characteristics of each cutting were noted: species; length in inches, rounded up to the nearest half inch; flowering, yes or no; mangled, yes or no. If the cutting was unrecognizable, the species was counted as other. A cutting was classified as flowering if it had flowers, buds, or a flower stem. A cutting was classified as mangled if it was severely damaged or if it had partial leaves or damaged stems due to the mechanical act of harvesting. Cuttings classified as mangled were ones that would likely be thrown out if the goal were 100 percent propagation success. After the data about the cuttings were collected, the cuttings were spread back into the treatment area from which they were harvested. The cuttings were spread by throwing them onto exposed media until all the collected cuttings were dispersed. An attempt was made to evenly cover the bare patches and to avoid throwing cuttings on existing plants.

57 48 Care and Maintenance Both of the cutting harvest days were followed by heavy rain. The first harvest was followed immediately by heavy rain. The rain that fell on 28 May 2009 began immediately after the cuttings were harvested and spread and continued over night. The cuttings were watered again by hand on 1 June, 2009 immediately following the dispersion of cuttings harvested on that date. Figures 4-4 and 4-5 show daily rainfall and daily high and low temperature respectively for the months of May and June The summer during which this experiment occurred was relatively wet and cool, so drought stress was not much of an issue. The weather allowed weeds to grow well. The weather data were collected by Weather Observatory in the Department of Meteorology at The Pennsylvania State University (Syrett, Personal Communication., 2010). The weather station was located on the University Park campus at the Walker Building. Rainfall (cm) /26/2009 5/27/2009 5/28/2009 5/29/2009 5/30/2009 5/31/2009 6/1/2009 6/2/2009 6/3/2009 6/4/2009 6/5/2009 6/6/2009 6/7/2009 Date

58 Figure 4-4: Graphical representation of the rainfall between 5/1/2009 and 6/7/2009. Cuttings were harvested on 5/28/2009 and 6/1/ Degrees C /1/2009 5/11/2009 5/21/2009 5/31/2009 6/10/2009 High Temperature Low Temperature 6/20/2009 6/30/2009 Date Figure 4-5: Daily High and Low Temperatures from 5/1/2009 to 6/30/2009 Data Collection New plant data were collected on two days in October: 1 October, 2009 and on 28 October, The first hard frost occurred on 14 October, 2009 which was in between the two days of data collection. The Sedum species surveyed were hardy and undamaged by the frost. New plant data were collected following the description in Chapter 4-2.

59 50 Statistical Analysis New plant density data were analyzed using Minitab Statistical Software produced by Minitab Inc., State College, Pennsylvania. A one way analysis of variance (ANOVA) was used to determine the differences in mean new plant densities. A two sample T-test was used as a secondary test to confirm that the mean new plant density was different between reel mower and string trimmer treatments. An ANOVA was also used to determine whether there was a statistical difference in the percentage of flowering and damaged cuttings between harvesting tools. Results of the statistical tests are found in Appendix E: Statistical Output.

60 51 CHAPTER 5: OUTDOOR EXPERIMENT RESULTS AND DISSCUSSION Chapter 5-1: Explanation of the Proposed Maintenance Method The maintenance method proposed in this experiment was designed specifically to propagate new Sedum plants on a green roof in places where growing media was exposed due to poor plant coverage. The source of cuttings was Sedum plants already established on the same green roof. Because Sedums were so easy to propagate from cuttings, cuttings provided a reliable source of new plants. This method was designed to decrease long term maintenance costs by minimizing the need for new plants, labor, and fertilizer. Instead of using this method, new nursery plugs and cuttings could be purchased directly from a plant nursery. However, there would be drawbacks to using nursery plants. The cost of new nursery plants is one reason to avoid ordering them. At the time of this thesis, the price of new Sedum plugs from Emory Knoll Farms started at $0.63 each. At the recommended planting density of 23 plugs per m 2 (2 plugs/ft 2 ), the cost of new plugs was $14.49 per m 2 ($1.26/ft 2 ). Cuttings of assorted Sedum species sold by Emory Knoll Farms were available in pound boxes for $300. The cost of cuttings per unit of roof area was approximately $3.20 per m 2, ($0.30/ft 2 or $300/1000 ft 2 ) (Snodgrass, Personal Communication. 2009). Shipping costs were not included in the plant prices and would vary depending the location of a project. Sedum plants growing on a green roof could provide copious and free cuttings for a maintenance worker to propagate.

61 52 Ordering new plants also involves advanced planning and scheduling on the part of the maintenance person or company. Plugs and cuttings from a third party must be ordered in advance and shipped to a project location to coordinate with installation. Once plants arrive on site, they must be unpacked immediately and cared for until they are planted. If cuttings are purchased, they must be spread almost immediately or else they will die. Planting can be delayed due to weather conditions thus disrupting ongoing installations, and delays in planting greatly increase the risk of plant loss. By avoiding the use of commercially available nursery plants, the method proposed in this thesis eliminates the cost of plant material and shipping, reduces the risk of plant loss due to weather delays, increases the flexibility of a maintenance schedule, and reduces fossil fuel consumption related to shipping. Chapter 5-2: Efficacy of Treatment The process of harvesting and spreading cuttings described previously did result in the establishment of new Sedum plants. The efficacy of treatment was confirmed by comparing densities of new Sedum plants in treated and untreated sections at the end of the growing season. Density was measured as the number of new Sedum plants per square meter of exposed media. The mean new plant density was significantly greater in treated sections than in control sections. Figure 5-1 and Table 5-1 compare new plant densities. Despite the fact the treatments were replicated six times in six different roof sections, only five sections were sampled for new plants.

62 53 New Plant Density (NP/m 2) c bc b a Control Hand Sheers Reel Mower String Trimmer Treatment Figure 5-1: The mean number of new Sedum plants per square meter for each treatment. The error bars show standard error. Control sections showed significantly lower new plant density than any of the treatments (p = 0.00). The string trimmer showed significantly lower new plant density than the reel mower (p = 0.036). The new plant densities of hand shear and reel mower treatments were not significantly different. Table 5-1: Data table showing the mean number of new Sedum plants per square meter for each treatment. Control sections showed significantly lower new plant density than any of the treatments (p = 0.00). The string trimmer showed significantly lower new plant density than the reel mower (p = 0.036). The new plant density of hand shears and reel mower treatments was not significantly different. Treatment Mean Density NP/m 2 (NP/ft 2 ) Area Sampled m 2 (ft 2 ) Control 24 (2) 2.88 (31) Hand Shears 121 (11) 2.04 (22) Reel Mower 159 (15) 1.95 (21) String Trimmer 96 (9) 2.60 (28)

63 54 Though no cuttings were spread, new plants established themselves in control sections by unassisted, natural propagation. Sedum species are quite capable of slowly reproducing vegetatively and by seed, so new plants were expected to gradually fill in areas of exposed media. No attempt was made to restrict or control the natural spread of Sedum species in control sections. Chapter 5-3: Cutting and New Plant Species Compositions As hypothesized, there was a relationship between the species of the cuttings harvested in May and the species of the new plants counted in October. Table 5-2 compares the species composition of cuttings and the species composition of new plants. Table 5-2: Comparison of the species composition of cuttings new plants from replications 1 through 5. Species % of Total Cuttings % of New Plants (Control Sections) % of New Plants (Treated Sections) S. acre 2% 0% 7% S. album 38% 51% 35% S. rupestre (Angelina) <1% 0% 0% S. kamtschaticum <1% 0% 0% S. hispanicum <1% 0% 0% S. rupestre 1% 9% 3% S. sarmentosum 8% 0% 8% S. sexangulare 23% 31% 31% S. spurium 20% 3% 13% S. spurium (Fuldaglut) 8% 6% 3% Other <1% <1% <1% Sample Size As expected, Table 5-2 demonstrated that the maintenance method proposed in this thesis was only effective at propagating plants that were present on a roof at the beginning of the

64 55 season. The percentages shown were measured as the number of cuttings of new plants of a single species divided by the sample size. The ratio was then multiplied by 100. Control sections were separated from treated sections when calculating the percentages of new plants reported in Table 5-2. These data also demonstrated that all the species tested, except S. rupestre (Angelina) S. hispanicum, and S. kamtschaticum could be relied upon to produce viable cuttings. Cuttings from the three aforementioned species were tested for viability in the greenhouse portion of these experiments, and they were found to produce viable cuttings. The relatively large percentage of new S. acre plants compared to S. acre cuttings was notable and likely due to the species ability to reseed itself. In another study, Sedum acre and Sedum album were found to be the dominant species after one year on experimental green roofs planted from seed, suggesting that these two species were relatively aggressive spreaders (Monterusso, et al. 2005). This phenomenon was also reported by Durhman et al. (2004). Durhman et al tested 25 succulent species and found that S. acre, S. album, and S. hispanicum were among the 5 species with the fastest growth rate and greatest area coverage after one growing season. It is likely that the low number of S. hispanicum and S. acre cuttings was likely the result of those plants being very small when cuttings were harvested, making them difficult plants from which to collect cuttings. S. acre may be underrepresented in the new plant data shown in Table 5-2 due to sampling difficulty. In areas of Sections 3 and 4 (Figure 4-2 or Appendix A), areas of exposed media at the beginning of the season were almost fully covered with new S. acre plants at the end of the season. These areas were not sampled because the number of new plants was too high to count. New S. acre plants were tiny and numerous, making them very difficult to evaluate as new and difficult to quantify, even in such a small survey area.

65 56 Sedum hispanicum has also been observed to have prolific reseeding abilities (Durhman et al. 2007). Its reseeding ability may account for the large patches of S. hispanicum on this experimental roof despite the very small number of S. hispanicum cuttings. S. hispanicum flowers throughout June and July with seedlings appearing by early August. Chapter 5-4: Comparison of Harvesting Tools Efficiency The tools used in this experiment were chosen for specific reasons. Portability and mobility were important because access to a green roof may be limited to a ladder or a small access staircase. Additionally, tools used on green roofs should not require an electrical outlet, as it may be difficult to find a suitable outlet or long enough extension cord to allow use of the tool over several hundred to several thousand square meters of roof area. Battery powered devices may be useful, but a long battery life would be required. The three tools chosen, hand shears, a manual reel mower, and a gasoline powered string trimmer met these preliminary criteria of green roof suitability. The time required to harvest cuttings from the 397 m 2 experimental roof is displayed in Figure 5-2 and Table 5-3. Time values were calculated by first measuring the time required to complete a single treatment. Using the area of the treatment, the time was converted to time required to treat 1 m 2 (seconds/m 2 ). The mean time required to treat 1 m 2 was calculated for each tool. The mean time was then multiplied by the area of the roof, 397 m 2, to estimate the time required to harvest cuttings from the entire roof. Table 5-3 displays time expressed as hours:minutes:seconds (hh:mm:ss) to treat 1 m 2 and the entire roof.

66 57 Time (hh:mm:ss) 4:48:00 4:19:12 3:50:24 3:21:36 2:52:48 2:24:00 1:55:12 1:26:24 0:57:36 0:28:48 0:00:00 3:42:58 2:01:47 1:12:09 1:13:19 Hand Sheers (long) Hand Sheers (short) Reel Mower String Trimmer Treatment Figure 5-2: The estimated time required to cut the entire roof (397 m 2 ). The times reported in Figure 5-2 only included the time required to cut parent plants. The times did not include the time required to collect and spread any cuttings. In theory the tools themselves could be used for cutting dispersal. The operator of hand shears could manually disperse cuttings while continuing to take more cuttings. A simple flick of the wrist dispersed cuttings while using hand shears. The reel mower and string trimmer both dispersed cuttings away from the parent plant. Both the reel mower and the string trimmer also provided the operator with some control over the direction and distance of cutting dispersal. The reel mower tended to throw cuttings straight forward and backward along the axis on which it was rolling. The distance of cutting dispersal could be controlled somewhat by the speed at which the mower was pushed. The string trimmer tended to throw the cuttings to its sides in the direction that the string rotated. The distance of cutting dispersal could be manipulated by adjusting the engine throttle and string speed. With both the mower and the string trimmer, the operator gained a sense of how to orient the tool to directionally disperse cuttings.

67 58 The difference in time to cut parent plants with a string trimmer and the reel mower was negligible, and both were significantly faster than using either set of hand shears. It was important to note however that, if a string trimmer were actually used on the entire roof, it would likely need to be refueled at least once, adding an additional few minutes to the treatment time. The author also observed that using hand shears caused more fatigue than using either the reel mower or string trimmer. This meant that a harvester using hand shears would likely become less efficient as fatigue set in. Therefore, it was reasonable to assume that the actual harvesting time for the entire roof using a string trimmer or hand shears would be longer than the projected time reported in Figure 5-2 and Table 5-3. The switch from the long handled Hound Dog shears to short handled shears was clearly justified by the difference in time required to harvest cuttings. Chapter 5-5: Comparison of Harvesting Methods - Cutting Quality In addition to being evaluated by efficiency, the different harvesting tools were evaluated by the quality of the cuttings produced. Individual cutting quality was evaluated by whether the cutting was visibly damaged or mangled and by whether it had buds or flowers. Cuttings classified as either damaged or flowering were ones that the author would discard if 100 percent propagation success were the objective of treatment. This did not necessarily mean that such cuttings would not propagate successfully, but successful propagation was less likely. Table 5-4 shows the percentage of cuttings damaged by each tool. Table 5-5 shows the percentage of cuttings that were flowering at the time of harvest. Flowering was used as a measure of cutting quality because the harvester had the ability to select parent plants that were not flowering. The control given by the harvesting tool affected how easily plants could be selected based on

68 flowering. As mentioned in the literature review, flowering cuttings were likely less viable than non-flowering cuttings. 59 Table 5-4: Comparison of damaged cuttings taken by each harvesting tool. The percentage of mangled cuttings is significantly different for all three treatments. Treatment Damaged Cuttings Total Cuttings (Sample Size) Percentage of Damaged Cuttings Hand Sheers % Reel Mower % String Trimmer % Table 5-5: Comparison of the flowering cuttings taken by each harvesting tool. The reel mower and string trimmer produced significantly more flowering cuttings than hand shears. Treatment Flowering Cuttings Total Cuttings (Sample Size) Percentage of Flowering Cuttings Hand Sheers % Reel Mower % String Trimmer % Based on the percentages of damaged and flowering cuttings, hand shears yielded the highest quality cuttings. Hand shears gave the harvester more blade control than the other tools, and they cut plants in a less violent manner. Hand shears also allowed the harvester to straighten stems before taking cuttings, which helped reduce damage. The added blade control allowed the harvester to select plants that were not flowering. At the time of cutting harvest, a number of species, particularly S. sexangulare were beginning to flower, so it was impossible to completely

69 60 avoid taking some cuttings that were flowering and still complete the treatment in a reasonable time. The difference in cutting quality between cuttings harvested with a reel mower and a string trimmer could have affected the density of new plants shown in Figure 5-1 and Table 5-1. Lower cutting quality should theoretically decrease cutting viability, thereby reducing new plant density at the end of the season. The data showed that the string trimmer produced the lowest quality cuttings and also returned a lower new plant density than the reel mower. Chapter 5-6: Other Observations from the Roof A large number of cuttings disappeared off the surface of the outdoor green roof by 22 June, 2009, three weeks after cuttings were harvested and spread. The cuttings may have died because they dried out or rotted, or may have been moved by wind, animals, or rain. It was also observed that roots on the new cuttings that were not growing down into the media by 6/22/2009 were shriveled and dead. These observations indicated that the first three weeks after the cuttings were spread were critical to the survivorship of Sedum cuttings, and ultimately the success of the maintenance method proposed in this thesis. These observations led to the greenhouse experiments described later. Robert Cameron, a Ph. D. student under Dr. Robert Berghage, ran a gasoline powered rotary mower across the roof during the late summer. He set the blades as high as possible so that they did not cut any of the Sedum foliage. His goal was cutting down the aforementioned horsetail because it gave the roof a ragged appearance. Robert Cameron observed that the mower in addition to cutting down the weeds, the mower also removed seed pods, dispersing Sedum

70 61 much of the seed produced that year (Cameron, Personal Communication., 8/2009). However, Kathryn Sanford, another Ph. D. student under Dr. Robert Berghage, studying Sedum seed viability, noted that the seed she harvested from this experimental roof demonstrated extremely low viability (Personal Communication., 2/2010). Therefore, caution should be used if dispersing seed to increase vegetative is the primary goal any future treatment. In addition to dispersing seed, deadheading the plants has an aesthetic value. Seed pods may be considered unsightly by some people because they are brown and twiggy in appearance, so there is subjective aesthetic value to removing seed pods.

71 62 CHAPTER 6 GREENHOUSE EXPERIMENT INTRODUCTION A greenhouse experiment intended to evaluate the effects of irrigation on the rooting of sedum cuttings, and to test the viability of sedum cuttings harvested from the experimental green roof was conducted during the summer and fall of The experiments were conducted in a computer controlled section of a greenhouse behind the Tyson Building on the University Park campus. The greenhouse experiments were designed to closer analyze how sedum cuttings root and survive during the first three weeks after being spread on green roof growing media. When discussing sedum propagation, Ray Stephenson author of Sedum: Cultivated Stone Crops wrote, Unlike mesophytes that relish a watering-in process, Sedum cuttings are likely to rot if watered immediately. By waiting at least three days so that tissue damage has had time to callus, rot is unlikely and small rootlets are likely to have formed to make use of the delayed moisture (Stephenson, 1994). If this statement held true for all the Sedum species used in the outdoor experiment, then many of the cuttings might have rotted and died because they were immediately soaked by heavy rain or manual irrigation after being dispersed. However, when flats of sedum plugs were propagated at Emory Knoll Farms Inc., cuttings usually were not allowed to callous before they were stuck in growing media and watered in. Propagation flats in the nursery were filled with media and watered prior to cuttings being stuck. The flats were watered again immediately after cuttings were stuck, and then watered daily for a few more days. This treatment of sedum cuttings stands in contrast to Stephenson s recommendations, but still resulted in successful commercial propagation of Sedums.

72 63 Stephenson s recommendation to allow three days before irrigating may be due to the way in which he recommended propagating cuttings. He recommended sticking cutting into growing media, whereas this maintenance method proposed setting the cuttings on the surface of coarse growing media. When cuttings are stuck in growing media, they do not have the same amount of aeration, which could be the cause for rotting. By laying the cuttings on top of the growing media, they receive more oxygen because air can move freely around the entire cutting. Despite the difference in propagation methods, there was merit to studying the effects of irrigation on the rooting of sedum cuttings. If the maintenance method put forth in this thesis were used commercially, watering a green roof the same day cuttings were harvested would be logistically easier and more efficient than allowing cuttings to callous for three days before irrigating. Immediate irrigation avoids sending a worker to the same roof more than one time. It also meets the FLL recommendation that only one or two maintenance visitations should be made to an extensive green roof each year. However, if Stephenson is correct and sedum cuttings rot when they are not allowed to callous, then irrigating immediately following cutting harvest may lead to complete failure of the treatment. The cuttings in the outdoor experiment were watered immediately following treatment. The difference between Stephenson s recommended propagation method and the way that sedum cuttings are propagated in the experiment is that Stephenson recommends sticking the cutting into compost, whereas this method proposes laying the cutting on top of coarse, granular media. There are differences in aeration and moisture between these techniques, so cutting laid on top of green roof media may be less susceptible to rot because they have better flow.

73 64 A second greenhouse experiment tested the viability of Sedum species collected from the green roof. Species that were completely non-existent or underrepresented in the cutting mix found in the outdoor experiment were specifically chosen for the second greenhouse experiment. Chapter 6-1: Goals and Objectives The first goal of the first greenhouse experiment was to show that cuttings of some Sedum species would survive immediate and prolonged irrigation without rotting. The objectives of the first experiment were to determine if cuttings from four Sedum species would rot if they were kept constantly moist for three weeks. The goal of the second greenhouse experiment was to determine if all the species on the green roof produced viable cuttings. Specifically the second experiment analyzed rooting of cuttings from Sedum species that were either completely absent or poorly represented in the cuttings mixture found in the outdoor experiment. The specific species of interest were S. acre (aureum), S. album (flowered out), S. kamtschaticum, S. hispanicum, and S. rupestre (Angelina), S. sarmentosum, and S. spurium (Fuldaglut).

74 65 Chapter 6-2: Hypotheses 1) Cuttings would rot when irrigated immediately after being spread on the surface of green roof media. This is based on Ray Stephenson s recommendations. 2) One hundred percent (100%) of the cuttings send out roots regardless of watering regime. 3) All the Sedum species from the roof would produce viable cuttings, including S. album plants that flowered vigorously all summer.

75 66 CHAPTER 7 GREENHOUSE MATERIALS AND METHODS Chapter 7-1: Materials Pots 8 inch bulb pans from Dillen Products/Myers Industries, Inc., Middlefield, Ohio (Dillen Products, Inside diameter = cm (8 in) Outside diameter = cm (8 1/8 in) Depth cm (4 in) Volume 2.47 L (2.62 qt) The cm (8 in) size was chosen because it allowed an individual plug 324 cm 2 (50.3 in 2 ) of area. This was approximately the area given to each plug when a roof is planted with a density of 23 plugs per m 2 (2 plugs per ft 2 ). Growing Media The growing media used was Rooflite extensive green roof media supplied by Laurel Valley Farms, Avondale, Pennsylvania. Full media specifications are included in Appendix C: Analysis of Rooflite Green Roof Growing Media

76 67 Plant Material Plants were taken out of 72 cell, 8.9 cm (3 in) deep plug trays. Plugs were supplied by Emory Knoll Farms Inc., Street, Maryland. The four Sedum species used in the experiment were S. album, S. sexangulare, S. kamtschaticum, and S. spurium (John Creech). These four species were chosen because of their prevalence on the outdoor experimental green roof used is study. The four species were also common green roof plants and were listed on Emory Knoll Farm s list of recommended green roof plants ( The plugs were grown to supply cuttings for the first greenhouse experiment that tested watering regimes. The cuttings for the second experiment were taken from established plants on the experimental green roof. Chapter 7-2: Methods Growing a Cutting Stock Bulb Pan Preparations Each bulb pan was filled to the top with media. Each pot was topdressed with a heaping teaspoon (8 g) of Osmocote fertilizer. This rate of fertilization fell within the medium rate of 9-15 g per gallon prescribed on the back of the Osmocote bag. Fertilizer granules were spread evenly across the surface of the growing medium by hand.

77 68 Planting - 4/14/2009 A single plug was inserted into the center of each bulb pan. Before being planted, the root balls were gently rubbed between the fingers to unbind the roots. The pans were randomly placed on greenhouse benches. After the plugs were planted, all pans were watered to runoff. All plants were watered twice weekly until cuttings were harvested on 14 September, The greenhouse was kept at approximately 21 /16 C (70 F/ 60 F) day/night temperatures. Chapter 7-3: Methods - Watering Regime and Greenhouse Cutting Viability Tests Experimental Design The experiment was conducted as a randomized block design. Bulb plans were prepared as described in Chapter 7-2, but no plugs were planted. The pans were fertilized in April and not again before cuttings were spread in September, The non-vegetated bulb pans were arranged into blocks of 16 pans (4 pans x 4 pans). Each of the four species listed in the plant material section of Chapter 7-2 was randomly assigned to four pots. Each pot was then randomly assigned one of the four watering regimes so that one pot of each species received each watering regime. The watering treatments were daily watering, 1 day between watering, 7 days between watering, and 14 days between watering. The entire experiment was replicated three times.

78 69 Harvest and Weigh Cuttings Cuttings were harvested on 14 September, 2009 from the stock plants grown from nursery plugs as described in Chapter 7-2. By the time plants were harvested, they were very large and many had sent shoots out of their own pan. In some cases, shoots had begun to root in adjacent pots. Scissors were used to harvest 3.8 cm (1.5 in) cuttings from the tips of established plants. Cuttings were separated by species and placed in brown paper lunch bags for transportation to a lab where they were weighed. Ten cuttings of each species were weighed at a time. Spread Cuttings Ten cuttings of one species (S. album, S. sexangulare, and S. spurium (John Creech)) were placed on the surface of the growing media in a single bulb pan. Due to their size, only 4 cuttings of S. kamtschaticum were placed on the surface of the same sized bulb pan. All cuttings were oriented in the same direction and were not touching. In two replications, cuttings were spread on 14 September, In the third replication, cuttings were spread one week later, on 21 September, Watering All bulb pans were watered to saturation immediately after cuttings were spread. After the first irrigation, one bulb pan of each species received each of the following watering treatments: daily watering, watering every other day (1 day between watering, 1 DBW),

79 70 watering on spreading and at day 8 (7 DBW), and watering at planting with no additional watering (10 DBW). All bulb pans were watered by hand to avoid cross watering. Water was evenly distributed across the surface of the pan, so all cuttings received direct contact with overhead water. Pans were watered to runoff. Data Collected Collected Daily Cuttings were carefully monitored for the presence of roots. The ratio of cuttings showing roots to total cuttings was noted daily. A pen or pencil was used to move the cuttings so small roots could be seen. The cuttings were monitored for the presence of roots daily for 9 days. Chapter 7-4: Methods Outdoor Cutting Viability Cuttings from the experimental green roof were propagated to test whether certain species produced viable cuttings. The bulb pans used in this experiment were the same as the ones used in Chapter 7-3. Media were prepared the same way as described in Chapter 7-3. The species tested were S. acre (aureum), S. album (healthy, collected in October) S. album (flowered out), S. hispanicum, S. kamtschaticum, and S. rupestre (Angelina), S. sarmentosum, S. sexangulare (healthy, collected in October), and S. spurium (Fuldaglut). Harvesting Cuttings Scissors were used to harvest 3.8 cm (1.5 in) cuttings from the tips of established plants on the outdoor experimental green roof. Cutting were separated by species and placed in a brown

80 71 paper lunch bag for transportation to a lab where they were weighed. Ten cuttings of each species were weighed at a time. Spreading Cuttings For the watering regime experiment, 10 cuttings of S. album, S. sexangulare, and S. spurium (John Creech) were placed on the surface of one 8 bulb pan. Due to their size, only 4 cuttings of S. kamtschaticum were placed on the surface of the same sized bulb pan. All cuttings were oriented in the same direction and were not touching. For the cutting viability test, 12 to 20 cuttings were placed on the surface of the bulb pan. Again the exception was S. kamtschaticum, and only 4 cuttings of this species were placed on the surface of a bulb pan. The specific number of cuttings of each species can be seen in Table 8-1. Watering Cuttings were watered twice a week. The greenhouse temperatures were raised to 27 /16 C (80 /60 F) day and night temperatures during this experiment. The temperature was raised so the growing media could dry out between watering. Data Collection Cuttings were checked weekly for the presence of roots.

81 72 CHAPTER 8: GREENHOUSE EXPERIMENT RESULTS AND DISCUSSION Chapter 8-1: Watering Regime and Greenhouse Cuttings Viability 100% 90% Percent of Rooting Cuttings 80% 70% 60% 50% 40% 30% 20% 10% 0% Days After Spreading Daily 1 DBW 7 DBW 10 DBW Figure 8-1: Rooting data for S. album collected in the greenhouse. Thirty cuttings were sampled

82 73 Percent of Rooting Cuttings 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Days After Spreading Daily 1 DBW 7 DBW 10 DBW Table 8-2: Rooting data for S. sexangulare collected in the greenhouse. Thirty cuttings were sampled 100% 90% Percent of Rooting Cuttings 80% 70% 60% 50% 40% 30% 20% 10% 0% Days After Spreading Daily 1 DBW 7 DBW 10 DBW Table 8-3: Rooting data for S. kamtschaticum collected in the greenhouse. Twelve cuttings were sampled.

83 74 Percent of Rooting Cuttings 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Days After Spreading Daily 1 DBW 7 DBW 10 DBW Table 8-4: Rooting data for S. spurium (John Creech) collected in the greenhouse. Thirty cuttings were sampled. There were no differences in rooting observed for S. album, S. sexangulare, and S. spurium (John Creech). No cuttings rotted and died. The results suggest that when placed on green roof growing media, there is no reason to allow Sedum cuttings to callous for three days before irrigation. S. kamtschaticum cuttings were much slower to send out roots. Once they appeared, the roots of S. kamtschaticum were thicker and appeared to have more root hairs than the roots of the other species. Eventually all the S. kamtschaticum cuttings did root, but not in the 10 days when they were observed daily. The number of days to 100 percent S. kamtschaticum rooting was not noted. The first greenhouse experiment demonstrated that cuttings of the four Sedum species tested did not rot and die under the conditions this experiment, which was intended to mimic

84 75 moderate conditions on an outdoor green roof. This finding suggested that irrigating a green roof immediately after cuttings are spread on its surface will not result in cutting mortality due to rot. This has important ramifications for the practical application of the maintenance method proposed in the outdoor experiment potion of this thesis, because immediate irrigation allows a single maintenance trip to be made, during which time cuttings are harvested, collected, and watered. Chapter 8-2: Outdoor Green Roof Cutting Viability Results Table 8-1: The percentage and ratio of cuttings from the experimental green roof rooting 7 days after being spread on green roof growing media. Species Percent of Rooting Cuttings After 7 Days Ratio of Rooting Cuttings After 7 Days S. acre 100% 17/17 S. album (Healthy) 100% 12/12 S. album (Flowered Out) 100% 15/15 S. hispanicum 100% 15/15 S. kamtschaticum 75% 3/4 S. rupestre (Angelina) 100% 15/15 S. sarmentosum 100% 13/13 S. sexangulare (Healthy) 100% 20/20 S. spurium Fuldaglut 100% 15/15 Cuttings from S. album plants that had flowered all season were viable. Those cuttings are labeled in Table 8-1 as S. album (Flowered Out). These data showed that all the species of Sedum present on the outdoor green roof produced viable cuttings. As mentioned in the outdoor experiment section, some species were not well represented in the cutting or new plant mixes.

85 76 The data also show that S. album (Flowered Out) was capable of producing viable cuttings after flowering all summer. The S. album parent plants appeared very tired and weak, but they still produced viable cuttings. These data demonstrated that S. album still produced viable cuttings after flowering, even though sedums tend to produce less viable cuttings after the flower (Snodgrass, 2006.) cuttings could be harvested in the fall, after the parents plants have flowered all summer, and the cuttings can be expected to root. S. album also has a tendency to flower itself to death some years (Berghage, Personal Communication, 2009). Because the cuttings are still viable, S. album plants that flowered vigorously could be cut back, the cutting spread, and should re-establish the same patch of vegetation the following year.

86 77 CHAPTER 9: THESIS CONCLUSIONS Efficacy of Treatment Compared to control sections, all of the treated sections showed greater densities of new Sedum plants, despite cutting losses due to drying out, rotting, and being removed by wind and potentially animals. Therefore the maintenance method put forth in this thesis met its primary goal of increasing the number of Sedum plants after one growing season. Comparison of Harvesting Methods By the measures of new plant density and efficiency, the reel mower was the most effective tool tested in this experiment. In the same amount of time, the reel mower produced fewer mangled cuttings and more new plants per square meter than the string trimmer. A reel mower had the added advantage of not using fossil fuel or electricity, so it was arguably the greenest tool used in this experiment. Considering that green roofs are a green technology, the greenness of a reel mower may be important to some green roof owners, installers, and maintainers. If cutting quality were the primary concern of the harvester, then hand shears were the best tools. Cutting quality may be the primary concern if cuttings were to be sold to third party or if a very small stock of cuttings were available. In either case, the control and discretion provided by hand shears made them a superior tool. However, hand shears were far too inefficient to be

87 78 useful on a 400 m 2 roof or anything larger. Arguably, they may be too inefficient for use on a roof half the size of the experimental roof. Irrigation Regime The greenhouse experiments demonstrated that irrigation can be applied immediately after cuttings are harvested and spread. Therefore, irrigation should be included in future applications of this maintenance method. By irrigation immediately after cuttings are harvested and spread, a maintenance worker can complete the maintenance in a single trip to the roof. By not waiting three days to allow cuttings to callous, this form of maintenance is logistically easier to perform, less time consuming, and therefore less expensive. Cutting Viability All the sedum species on this green roof, S. acre (aureum), S. album, S. kamtschaticum, S. hispanicum, S. rupestre, S. rupestre (Angelina), S. sarmentosum, S. sexangulare, S. spurium (White Form), S. spurium (John Creech), and S. spurium (Fuldaglut), did produce viable cuttings. This implies that this form of maintenance can be used on any sedum dominated extensive green roof. Given that extensive green roofs are considered low maintenance installations (FLL, 2006, Cantor 2008), this form of maintenance fits well within the maintenance guidelines of the FLL, which suggests only one or two maintenance visits per year on extensive green roofs. Limitations of the treatments

88 79 There was a major limitation in the method used in this experiment. Portions of a roof with large areas of exposed media were the same areas with the smallest stock of new cuttings. The same could be said of an entire roof. On a green roof showing very sparse vegetation, the method used in this experiment would likely perform poorly as a means of increasing plant coverage. Such a barren roof would need new plants from an outside source like a nursery because there would be a miniscule stock of cuttings on the roof. There might be a percent area coverage that acts as the balance point where this method would be effective and where new plants must be imported from an outside source. Based on personal experience and the results of this study, the author speculated that this method should be useful for attaining 100 percent coverage if 60 percent or more the roof is already covered with sedum plants. At a lower percent cover, outside plants would need to be purchased. This method would also prove ineffective on a roof where Sedum species, or other easily propagated species are not the dominate form of vegetation. Fortunately, the method is easily adaptable to overcome the aforementioned drawback. Constraining cuttings to the area from which they were harvested was adopted in this experiment solely to provide quantitative data for comparing treatments. On a roof like the one used in this experiment, cuttings could be easily harvested from one area where there is an abundance of available cuttings, like section 3-3, collected in a container, then spread on another area of the roof where there is an abundance of exposed media like section 1-1. Sections are those shown in Figure 4-2. Other Benefits of Treatment

89 80 Increasing the number of new plants was the goal of this treatment and that goal was met. However, the author noted there were some other benefits to the form of maintenance proposed in this thesis. The reel mower and string trimmer were also effective at cutting down weeds. Depending on the weather conditions, cutting down weeds would kill some of them. This experiment was conducted during a relatively wet and cool summer, so drought pressure never became a serious issue, and many of the weeds, most notably horsetail, grew back after being cut down. There were times when the weeds wilted, but they never reached the permanent wilting point. It was worth noting that the greatest concentration of horsetail was in Sections 1 and 6, shown in Figure 4-2. The growing medium in Sections 1 and 6 was about 15 cm (6 in) deep and the largest areas of exposed media. Other sections of the roof were built with 10 cm (4 in) of media depth, which means that Sections 1 and 6 retained more relatively water. Even if weeds were not killed by being cut down, cutting them down at the right time could prevent them from flowering and reseeding themselves. In the fall a similar treatment could be used, for the purpose of harvesting cuttings, and for the purposes of deadheading flowers, dispersing seed, and killing weeds. Robert Cameron, a Ph. D. student under Dr. Robert Berghage, ran a gasoline powered rotary mower across the roof during the late summer. He set the blades as high as possible so that they did not cut any of the Sedum foliage. His goal was cutting down the aforementioned horsetail because it gave the roof a ragged appearance. Anecdotal evidence suggested that the mower also removed seed pods, dispersing any Sedum seed (Cameron, Personal Communication., 8/2009). Seed pods may be considered unsightly by some people because they are brown and twiggy in appearance, so there is subjective aesthetic value to removing seed pods. If the seed were viable, dispersing it should lead to more new plants during subsequent growing seasons. However, Kathryn Sanford, another Ph. D. student under Dr. Robert Berghage, studying Sedum seed viability, noted that the seed she

90 81 harvested from this experimental roof demonstrated extremely low viability (Personal Communication., 2/2010). Therefore, caution should be used if dispersing seed to increase plant density is the primary goal of any future treatment. Further Research This experiment raised a number of questions that make excellent topics of further research. Interesting areas for further research include finding, adapting, or designing tools that optimized harvesting efficiency; evaluating this method for use in the second or third growing season of a new green roof plant establishment; determining the viability of Sedum cuttings after they experience a hard frost; and evaluating how much foliage can be removed from a single Sedum plant without killing it. Other tools should certainly be evaluated for harvesting efficiency and cutting quality. Some untested tools that may perform well in this method are long handled hedge trimmers or gasoline powered rotary mowers. Hedge trimmers generally have a long blade, which should effectively harvest a large quantity of cuttings with a single pass. Hedge trimmers may provide similar cutting quality as hand shears, because the harvester is provided similar blade control. A long handle will eliminate the need to bend or kneel while harvesting cuttings, so efficiency should be high and worker fatigue low. Gasoline powered, long handled hedge trimmers are commercially available from Stihl, makers of power equipment. Stihl long handled hedge models HL100 and HL 100K feature 20 inch blades and adjustable heads that allow the user to change the angle of the blade,

91 82 allowing it remain parallel to the surface of the green roof for optimal cutting harvest ( Gasoline powered rotary mowers also merit some consideration. A self propelled mower will cover a lot of area very quickly and will certainly cut back large weeds and old flower stems as noted. Research must determine if a rotary mower will actually produce viable cuttings. It is possible that the powerful mower will simply damage cuttings and parent plants beyond viability. Ideally any harvesting tool will combine a cutting mechanism and a collection mechanism in one tool. This will allow a maintenance person to harvest cuttings from densely vegetated areas of a roof and spread the cuttings on poorly vegetated areas without adding the extra step of using a vacuum to collect the cuttings. A potential addition to a reel mower would be a catcher designed to catch grass clippings as they are dispersed. A grass catcher may prove effective for collecting Sedum cuttings also. Grass catchers are commercially available for many manufacturers models of reel mowers. A new tool could be designed that combines a hedge trimmer similar to the Stihl product mentioned with a backpack vacuum or a cutting collection bin. The vacuum engine could be reversed so the vacuum also acts as blower to easily disperse cuttings. If a pressurized hose could be attached device, then a maintenance worker could harvest, collect, disperse, and water cuttings in a single pass, saving time and labor costs. Such a tool has potential to produce new intellectual property. The maintenance method put forth in this thesis could potentially be used as a standard operating procedure during the second or third year of a new green roof installation, or in

92 83 subsequent years if a roof experiences high plant mortality. The treatment has potential to encourage one hundred percent plant coverage faster and at a lower cost than increasing planting densities. If applied in the second growing season, pruning the previous year s plants may discourage flowering and encourage vegetative growth for a second season. The author notes that plugs of S. album, S. kamtschaticum, S. sexangulare, and S. spurium (John Creech) from Emory Knoll Farms Inc., planted in constructed boxes with 10 cm (4 in) of green roof media in his backyard in May 2009 did not flower. Also, no plugs out of about 200 of the same species flowered in a greenhouse on the University Park campus between April 2009 and February In addition to potentially encouraging vegetative growth, pruning in the second year should yield viable cuttings that will grow in the exposed media between the plugs installed the previous year. A concern is that the plants may not be established well enough to withstand the stress of being pruned during their second year on the roof. An interesting study would compare the percent area coverage to three planting treatments: Standard density, 23 plugs per m 2 (2 plugs/ft 2 ), and no treatment the second year; double the standard density, 46 plugs per m 2 (4 plugs/ft 2 ) and no treatment the second year; and 23 plugs per m 2 with treatment the second year. Plant area coverage would be measured upon planting, at the end of the first growing season, at the beginning and end of the second growing season, and at the beginning of a third growing season. The roof maintained by harvesting and spreading cuttings may show greater plant coverage than the control. Labor and plant costs should also be considered during this experiment. A third interesting research topic is the viability of Sedum cuttings after a hard frost. The author spread cuttings of S. acre and S. album in late October. The cuttings received a hard frost and were even blanketed in an early snow. It appears that they survived the cold and began

93 84 rooting, but the experiment was not controlled. If it can be demonstrated that certain species produce cuttings that are viable after a hard frost, then cuttings could be harvested and spread earlier in the spring, before the last day of frost occurs. Treatment in this experiment occurred in late May and early June, well after the last frost of the spring. If the treatment were applied earlier in the season, fewer established plants would be flowering, so theoretically the cuttings collected will be more viable. Also, the earlier cuttings are spread, the longer they have to establish strong roots in their first growing season. Additionally, if cuttings can be harvested and spread before the last frost, the maintenance person has more flexibility to perform this maintenance procedure. Testing for cuttings survival after frost would also show that this for of maintenance could also be used in the fall, and some cuttings could survive, root, and over winter. While testing the viability of cuttings after a hard frost, the survivability of established plants that are pruned then frosted should also be evaluated. This kind of treatment would be ineffective if the parent plants die, even if new cuttings survive. Finally, it may be worth evaluating what percentage of a Sedum plant can be taken as cuttings without killing the plant. The author removed nearly all of the foliage on S. album, S. kamtschaticum, S. sexangulare, S. spurium (John Creech) grown in a greenhouse for 6 months. Plants were left un-watered for weeks with day/night temperatures around 27 /16 C (80 /60 F) and had the added stress of a mealy bug population. Once watering began again, the plants responded by sending out new shoots, even plants that appeared completely dead began to grow again. This evidence is anecdotal because this was not a controlled experiment, but it suggests that established Sedum plants can survive extensive abuse.

94 85 Practical Applications of this Research The thesis showed that an green roof planted with sedum species provided cuttings capable of increasing the number of individual sedum plants where the roof showed areas of exposed media. Additionally, a method of harvesting and collecting cuttings with simple lawn maintenance tools such as a reel mower and a string trimmer. The results have very practical applications for green roof maintenance. Due to poor maintenance, green roofs commercially installed green roofs will show decreased plant coverage over time. So, some form of maintenance will be required to increased and maintain the coverage of desired plants. As show in Table 1-1, extensive green roofs are designed to be relatively low cost and low maintenance structures, so minimizing inputs of labor, new plants, and fertilizers during maintenance is import for minimizing long term costs. The form of maintenance put forth in this thesis requires relatively few man hours, and if combined with some hand weeding would provide excellent Sedum coverage. Excellent Sedum coverage is important to reducing weed populations because weed seeds tend to germinate only when media is exposed. For the best results, this form of maintenance should be used in the spring, before the parent plants begin flowering. This will yield more viable cuttings, and provide the cuttings the longest possible growing season in which to root and prepare to over-winter. If this form of maintenance is used in the fall, some propagations would be successful, though fewer cuttings should be expected to root and survive the winter as compared to cuttings spread in the spring and summer. A study at the Michigan State University found that 81% of plants survived over winter on green roof platforms when planted in the spring, while just 23% survived when planted in the

95 86 fall (Getter, et. al., 2007). All this information suggested that an existing roof should see the best results when cuttings are harvested and spread in the late spring or early summer, and not the fall. An advantage to a fall treatment is that flower heads can be removed, to give the roof a cleaner appearance. Additionally, a second maintenance visit in the fall allows the maintenance workers to fix any problems that may have occurred over the summer.

96 87 WORKS CITED Berghage, R. D., Beattie, D., Jarrett, A. R., & Rezaei, F. (2007). Green Roof Water Use. National Decentralized Water Resources Capacity Project, Berghage, R. D., Beattie, D., & Negassi, A. (2007). Green Roof Capacity to Neutralize Acid Runoff. National Decentralized Water Resources Capacity Project, Cameron, R. D. (2009). Personal communication Cantor, S. L. (2008). Green roofs in sustainable landscape design. New York, NY: W.W. Norton and Company, Inc. Compton, J., S., & Whitlow, T. H. (2006). A zero discharge roof system and species selection to optimize evapotransiration and water retention. Greening Rooftops for Sustainable Communities, Boston. Dillen Products/Myers Industries, I. (2010). Dillen products - molded plastic products for horticulture. Retrieved 3/4/2009www.dillen.com Emilsson, T. (2008). Vegetation Development on Extensive Vegetated Green Roof: Influence of Substrate Composition, Establishment Method, and Species Mix. Ecological Engineering, 33, 265. Emory Knoll Farms, I. (2007). Green roof plants. Retrieved 3/4/2010, 2010, from Getter, K., & Rowe, D. B. (2007). Effect of substrate depth and planting season on sedum plug establishment on extensive green roofs. Greening Rooftops for Sustainable Communities, Minneapolis.

97 88 Ingram, D. S., Vince-Prue, D., & Gregory, P. J. (2002). Science and the garden: The scientific basis of practical horticulture. Oxford, England: Blackwell Publishing. Jarrett, A. R., Hunt, W. F., & Berghage, R. D. (2007). Annual and Individual-Storm Green roof Stormwater ResponseModels. National Decentralized Water Resources Capacity Project, Montrusso, M., A., Rowe, D. B., & Rugh, C. L. (2005). Establishment and Persistence of Sedum Species and Native Taxa for Green Roof Applications. Hortscience, 40(2), Rowe, D. B., Rugh, C. L., & Durhman, A. K. (2006). Assessment of substrate depth and composition of green roof plant performance. Greening Rooftops for Sustainable Communities, Boston. Sanford, K. L. (February 2010). Personal communication Schmidt, M. (2006) The evapotranspiration of greened roofs and facades. Greening Rooftops for Sustainable Communities, Boston. Snodgrass, E. (February 2010). Personal Communication. Snodgrass, E., & Snodgrass, L. (2005). Green roof plants: A resource and planting guide. Portland, OR: Timber Press. Stephenson, R. (1994). Sedum: Cultivated stonecrop. Portland, OR: Timber Press. Stihl Incorporated. (2010). Stihl. Retrieved 2/24/2009, 2010, from Syrett, B. (11/24/2009). Weather observatory, department of meteorology, the Pennsylvania State University

98 University Park Campus Maps with Building Indices (revised April 2009). Retrieved 2/23/2010, 2010, from 89 Vidmar, J., Kelley, K., & Berghage, R. D. (2007). Background, Educational, and Promotional Materials for Green Roofs: A series of Articles to Promote Understanding of the Benefits of using green roofs. National Decentralized Water Resources Capacity Project,

99 90 Appendix A A Collection of Vegetation Maps of the Experimental Green Roof Maps were drawn between May 18 th to 22 nd 2009

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107 98 Appendix B: A Collection of Vegetation Maps of the Experimental Green Roof from 2007 Maps were drawn by Kristen Casale

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