University of Tennessee Instructor Copy. Growing Vegetables in the 11Tennessee Home Garden NATALIE BUMGARNER

Transcription

1 Growing Vegetables in the 11Tennessee Home Garden NATALIE BUMGARNER Assistant Professor & Extension Specialist University of Tennessee

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3 CONTENTS INTRODUCTION 11-5 LOCATING AND PREPARING THE GARDEN SITE 11-5 Selecting the Garden Site Light Soil Characteristics Previous Site Activity Drainage Slope Other Considerations Soil Testing Site Preparation PLANNING AND PREPARING FOR THE GARDEN 11-8 Selecting Vegetable Crops for Growing Seasons Selecting and Ordering Seeds Selecting and Purchasing or Starting Transplants Locations and Materials Media and Fertilization Temperature Moisture Lighting PLANTING AND MANAGING THE GARDEN Seeding Transplanting ph and Fertility Management Initial Fertilizer Application Fertilization During the Growing Season Mulching Natural or Organic Mulches Inorganic Mulches Watering and Irrigation Overhead Irrigation Drip Irrigation Soaker Hoses Trickle or Drip Tape Soil Water Management Plant Maintenance Plant Support Ways of Supporting Vegetable Crops Stakes Cages

4 Trellises Stake-and-Twine Systems Pruning RAISED BED GARDENING Purposes and Benefits Raised Bed Design and Construction Materials Design Growing Medium Crops and Management Crops Management Irrigation Weeding, Mulching, and Rotation Support and Training EXTENDING THE GARDENING SEASON Cultural Practices that Can Extend Seasons Site Selection Raised Beds Transplants Temporary Methods and Structures Mulches Floating Row Covers Low Tunnels Shade Structures Permanent Structures Cold Frames High Tunnels Greenhouses STEWARDSHIP PRACTICES FOR THE HOME VEGETABLE GARDEN Supporting Soil Quality Nutrient Management Compost Crop Residues Cover Cropping Supporting Plant Health and Productivity Cultivar Selection Crop Rotation Supporting Biodiversity Integrated Pest and Disease Control Practices SUMMARY

5 SOURCE: Natalie Bumgarner, University of Tennessee INTRODUCTION Home vegetable production is both an important part of Tennessee culture and an area of increasing interest to homeowners. Home vegetable gardening can provide economic and nutritional benefits through ready access to fresh vegetables and enhances personal health and well-being through gardening activities. To take full advantage of these many benefits, it is important to understand and be able to share essential information about gardening practices. From soils and sites to crops and management methods, gardens in Tennessee are as diverse as the state s geography and climate, reflecting a wide range of practices. To meet these differing needs, this chapter provides an overview of key vegetable gardening topics. It is impossible for this manual to provide all the needed information, however, and many topics will require additional reading and research. In particular, it is always helpful to remain current on newly introduced plant cultivars. This chapter begins with the attributes of a productive garden site and how to prepare the soil. Next, characteristics of cool-season crops versus warm-season crops is presented, along with guidance on how to plan a garden that makes the best use of the season. Planting, watering, weeding, and plant maintenance are all addressed in the management section. The last few pages in this chapter delve into ancillary topics such as the use of raised beds and ways to extend the gardening season. By studying these topics, Extension Master Gardeners should find themselves prepared to answer questions about the installation of a healthy vegetable garden and to troubleshoot problems when confronted with unhealthy gardens. LOCATING AND PREPARING THE GARDEN SITE Watermelon Selecting the Garden Site LIGHT Selecting a garden location with adequate sunlight is one of the most important factors in 11-5

6 home vegetable production and sometimes one of the most challenging. Not only does sunlight provide energy for plant production and growth, but it also provides heat through solar radiation. Full sunlight is optimum for a garden, and a minimum of 6 to 8 hours of daylight should be provided for most crops. The garden should be located away from buildings or trees that would shade it. During summer, when the sun is high in the sky, trees will shade a smaller area. However, during the fall and spring seasons when the sun is lower in the sky, trees and other objects will cast longer shadows. Such shading is an important consideration if the gardener plans for early- or late-season production. Another way to consider lighting is the garden s aspect. Garden sites that face south or southeast often receive sunlight for longer periods of the day, and their soils also commonly warm up and dry out faster than soil on more protected north-facing sites. Temperatures may be more variable on southern sites, though. SOIL CHARACTERISTICS In addition to available light, characteristics of the soil on the potential garden site are also quite important. Not all soils are the same, and they vary in their ability to provide for plants. Soil provides physical support as well as access to water, nutrients, and air. Successful vegetable production is possible across a range of soils, but some may take more amending than others or require modified management practices. (See Chapter 6.) Ideal garden soils are of medium texture, meaning that they are a mixture of sand, silt, and clay, often referred to as a loamy soil. (See Chapter 5). Soils with high levels of clay are found in many areas of Tennessee and can hold water so tightly that it may not be available for plants, while sandy soils may not retain enough water or nutrients. Loamy soils provide a good middle ground for plant production. The way soil fits together called its structure is also important for gardening. Soil with good structure contains plenty of spaces for water and air to be held for access by plant roots, as discussed in Chapter 5. Addition of organic matter can improve soil structure, and this is one of the main reasons that adding materials like compost benefit the garden. Soil with more organic matter can lead to better water- and nutrient-holding capacity. (See Chapter 6.) Soils vary significantly across the state of Tennessee. It is important to understand the characteristics of soils in the local area. Soil test results (see Chapter 6) give specific recommendations for management. In addition, county Extension agents can provide valuable information on soil management in the area. Both of these types of information are important to get the most out of a home vegetable garden. PREVIOUS SITE ACTIVITY Knowing what has happened on the site in the past is important because construction may have compacted the soil and reduced the spaces for water and air, or native soil may have been removed to accommodate construction, or it may have been buried by development. For plant production, the A horizon (the topsoil) generally provides the best conditions for water, air, and nutrient access. It often has the highest amount of organic matter and the best structure. The B layer (called subsoil) may not be as wellstructured and usually does not contain as much organic matter. Layer C is material that is only one step away from bedrock. Most management practices for vegetable gardens focus on the upper 6 to 8 inches of the soil profile (as shown in the photo on page 11-7), which may include soil from both the A and B horizons. Over time, organic matter can be added and properties of subsoils improved, but vegetable gardening in native topsoil is ideal. Other information about previous activity on the potential garden site may include whether or not it was used recently for pasture production, is a former orchard site, has been used as a refuse area, or if previous or current uses include power-line or railroad rights-ofway. In all of these cases, there is a potential for the presence of residual pesticides, such as heavy metals in previous agricultural production areas or other materials that could affect vegetable production. DRAINAGE Ideal garden soils allow water to drain through the profile but also hold some water for plant 11-6

7 use. Soil texture greatly influences drainage, as large sand particles tend to allow water to drain faster than smaller silt and clay particles. Soils that are rich in clay more easily trap water and can be slow to drain. Loamy soil that has a mix of clay, sand, and silt often provides good intermediate drainage. The presence of organic matter can improve the ability of soil to hold water while also supporting structure and better drainage. SLOPE Slope, or change in elevation over distance, influences water infiltration. On steep slopes, precipitation is much more likely to run off rather than enter and move through the soil profile. Less infiltration and higher runoff of precipitation reduces the amount of water available for plants, and water moving across the soil surface can lead to erosion of topsoil. Gardening in an area with steep slopes and frequent erosion can reduce crop productivity while degrading soils for future use. In these situations, it is often best to select another location for the garden or add terraced beds. Slope can also influence the microclimate (climate conditions in the area immediately surrounding the plants). A slight slope can often allow cold air to drain down the slope and prevent it from settling and forming what is called a frost pocket. These small differences in temperature can be important in protecting crops in the spring and fall. Methods for protecting crops and extending the season are discussed later in this chapter. OTHER CONSIDERATIONS Accessibility for maintenance and harvesting, proximity of water for irrigation, and avoiding areas where soil has been degraded by previous use are also important. Look for weed problems, rocky or shallow areas, or other challenges that would reduce the potential for success. Keep in mind that poor soil conditions and heavy weed pressures can be addressed, but the time investment may significantly outweigh the benefit, especially early in the gardening journey. Soil Testing Soil testing can provide the gardener with important information needed to optimize SOURCE: Natalie Bumgarner, University of Tennessee productivity on the site. The most important thing to remember in soil sampling is that soil test results are only as good as the soil sample. See Chapter 6 for detailed descriptions of soil sampling methods. Site Preparation Proper preparation of soil helps germination and growth, and it can also help reduce maintenance during the growing season. All debris including rocks and any previous plastic mulches or plant supports should be removed. Crop debris should be composted or plowed into the ground only if it is disease free. If there was disease in Mediumtextured soil that is workable 6 to 8 inches deep is most desirable for gardens. 11-7

8 A smooth seedbed in a well-tilled and prepared garden. the previous crop, dead plant materials should be disposed of elsewhere. If the selected site is not currently in production, existing vegetation should be killed by herbicides, solarization (see Chapter 15), or mulching it or plowing it under. It is important to allow adequate time for the organic matter, such as sod, to break down after killing or tilling. Planting a new garden into recently tilled sod is a challenge for the gardener and can also potentially reduce crop productivity. A discussion of tillage practices may be found in Chapter 6. No-till practices can be used in many home vegetable gardens. If traditional tillage is chosen, garden soil should be mechanically tilled or worked by hand to provide uniform soil pieces to a depth of 8 inches if possible, as shown below. The amount of moisture present at the time of soil preparation is vitally important because working with soil when it is too wet can cause compaction and thereby reduce water infiltration and aeration. If a handful of soil sticks together when rolled into a ball and does not easily crumble, then the site is likely too wet to prepare. Patience in waiting for soil to dry to a level appropriate for working reduces compaction and provides future gardening benefits. PLANNING AND PREPARING FOR THE GARDEN Garden planning has the potential to save time, money, and space. Garden plans enable growers to allocate space for crops ahead of time, estimate seed quantities to improve economy, and provide a guide when seeding and transplanting time arrives. It is best to lay out the planting arrangement on graph paper or enter it into one of many gardening computer programs. This approach allows the gardener to visualize the garden and supports the efficient use of space and time. In addition, effective planning and record-keeping is an asset in cultural management and disease prevention because proper spacing and crop rotation can reduce disease pressure, as discussed later in this chapter. Selecting Vegetable Crops for Growing Seasons One of the most important considerations when selecting crops for home vegetable gardening SOURCE: Natalie Bumgarner, University of Tennessee 11-8

9 is an understanding of the seasons and temperature ranges to which each crop is best suited. Vegetable crops are generally grouped into two broad categories: warm-season and coolseason vegetables. Warm-season vegetables are most productive in higher temperature ranges (as in late spring and summer) and are better able to grow and produce a quality crop through Tennessee s summer heat. They are damaged or killed by frost and freezing conditions; even cool, nonfreezing temperatures may prevent them from growing and yielding well. Paying attention to local frost dates is especially important in selecting planting dates. Cool-season vegetables can withstand temperatures below 32 F (how far below varies with crop and situation), and they are generally more productive and have higher quality produce when grown during cooler spring and fall seasons. Because of these attributes, coolseason crops are planted early in the spring to avoid the hottest part of the summer and then can often be seeded again in late summer to provide for another crop during the fall season. Refer to Table 1 for a general listing of cool- and warm-season crops and planting seasons. Selecting and Ordering Seeds Selecting plant varieties for home gardens should be based on the level of disease resistance required, how well the growth habit of the crop will fit the garden space and cropping plan, and the taste preference of the gardener. UT Extension trial information is included in the supplementary digital materials. Procuring high-quality seed is essential for the home gardener so that garden space and time is not wasted on poor-quality seed or weak seedlings. Seed should be purchased from a reputable supplier for the current growing season and stored properly to ensure maximum productivity. Seeds should be stored in a cool, dark place where they will remain dry. An airtight container in the refrigerator is a practical option for the home gardener. Seed can be collected from previous crops in some instances, but caution is required. Many crops are hybrids, which means that the seed were produced from a cross of two specific parents to produce plants with desirable traits. A plant grown from seed collected from a hybrid plant will not have identical attributes to either parent, and it will often produce low yields or inferior produce. Seed should be saved only from nonhybrid crops. In addition, many diseases can be seed-borne, so collect and reuse seed only from healthy plants. Selecting and Purchasing or Starting Transplants There are two main methods of planting vegetables. The first is by directly seeding into well-prepared soil. The second is to purchase or grow plants for transplanting into the garden soil. Most gardeners use both methods, selecting some crops for direct seeding and others for transplanting. Both warm- and cool-season crops are commonly transplanted. (See Table 1). Some of the most common crops to be transplanted are tomatoes (see page 11-11), peppers, eggplants, cabbage, cauliflower, broccoli, and Brussels sprouts. While roots are somewhat tender in cucumbers, muskmelons, watermelon, and squash, these plants can also be transplanted if handled carefully. These crops can also be seeded in biodegradable pots so that roots will not need to be disturbed when planting into the garden. Large-seeded crops, such as beans, peas, and corn, as well as root crops, such as radishes, beets and carrots, are generally direct seeded. Home gardeners can purchase transplants at a greenhouse or garden center, but transplants can also be produced at home with proper care and attention. The latter can be an advantage in providing preferred or heirloom cultivars for your home garden. Keep in mind, though, that it will take several weeks preparation to have plants ready for transplanting into the garden at an appropriate time. (See Table 2.) Specific practices are discussed in the next section. When purchasing vegetable transplants from a greenhouse or garden center, select carefully. Choose healthy plants that are free from all signs of insects or disease, that are stocky, and that do not have damaged or yellow leaves. (See page ) Use care to select 11-9

10 TABLE 1 Suggested Planting Seasons and Methods for Common Vegetable Crops PLANTING TIME VEGETABLE EARLY TO MID-SPRING LATE-SPRING TO SUMMER SUMMER TO EARLY FALL Beans (bush/pole/lima) - seeds - Beets seeds - seeds Broccoli transplants - transplants Cabbage transplants - transplants Carrots seeds - seeds Cauliflower transplants - transplants Collards seeds or transplants - seeds or transplants Corn (sweet) - seeds - Cucumbers - seeds or transplants seeds or transplants Eggplant - transplants - Kale seeds or transplants - seeds or transplants Kohlrabi seeds or transplants - seeds or transplants Lettuce seeds or transplants - seeds or transplants Muskmelon - seeds or transplants - Mustard seeds - seeds Okra - seeds - Onions sets - - Peas (English/snap) seeds - - Peas (field/southern) - seeds - Peppers (sweet/hot) - transplants - Potatoes (Irish) seed piece - - Pumpkins - seeds or transplants - Radishes seeds - seeds Spinach seeds seeds (Malabar spinach) seeds Squash (summer/winter) - seeds or transplants - Squash (summer) - - seeds or transplants Sweet potatoes (slips) - transplants - Swiss chard seeds - seeds Tomatoes - transplants - Turnips (roots and greens) seeds - seeds Watermelon - seeds or transplants - HARVEST LATE SPRING/EARLY SUMMER SUMMER AND EARLY FALL FALL AND EARLY WINTER 11-10

11 SOURCE: Natalie Bumgarner, University of Tennessee plants that are not too old or stunted because very mature transplants (especially broccoli, cauliflower, and cucurbits) may not produce well after transplanting. Transplants should be a healthy green color to indicate that they are not nutrient deficient. This is not the time to shop for bargains because transplant health will often directly affect production. Also consider the conditions that the transplants are being grown in when purchased. Sometimes if purchased directly from a greenhouse, plants may not have been hardened off. This term refers to slowly subjecting plants to outside conditions more like those they will experience in the garden. This process lowers stress and loss when the plants are transplanted. Typically, plants are hardened for one to two weeks before transplanting them into the garden. See Table 2 for additional information on hardening vegetable transplants. LOCATIONS AND MATERIALS The best location for starting vegetable garden transplants is a home greenhouse. A greenhouse provides the opportunity to control temperature and humidity while maintaining optimum light. However, relatively few people have this option. Transplants can be started indoors if proper conditions, especially light and temperature, can be maintained. In addition, a cold frame or hotbed can be an economical and suitable location for starting transplants. The most common materials needed for transplant production are containers and equipment for temperature and light management. Containers, such as seeding flats and pots, are best purchased new or thoroughly cleaned and sterilized before reuse. The horticulture industry offers a large selection of pot sizes in plastic and biodegradable materials. MEDIA AND FERTILIZATION One of the advantages of vegetable transplants is that they can be started in a medium optimized for seed germination and young plant growth. Often the germination and growing medium used for transplant production is formulated from peat moss, as well as perlite, and vermiculite (superheated rock and clay materials). These materials provide optimum water-holding and aeration characteristics. All three of these materials can also be purchased in a premixed medium for seed germination. Fertilization depends upon the growing medium. Many mixes specifically prepared for seedling transplant production include Young tomato seedlings in the greenhouse 11-11

12 These tomato transplants show yellowed leaves caused by water or nutrient stress. Also visible is insect damage on the leaves. SOURCE: Natalie Bumgarner, University of Tennessee fertilizers to provide nutrients to the young plants. If using media without fertilizers included, add a premixed soluble fertilizer at half strength to the water used irrigate the seedlings once or twice a week. Monitor leaves for strong green color. Yellowing or purpling can suggest nutrient deficiencies or other issues with ph or temperature. (See Table 3.) TEMPERATURE For optimum germination and young plant growth, temperature is critical. In fact, poor germination is often caused by temperatures below or above optimum levels. Table 2 describes important temperature conditions for a range of common transplant crops. In general, temperatures for seed germination and seedling production (after germination) are lower for cool-season crops. Temperatures should be kept relatively consistent during germination. An electric germination mat can also be useful to provide the optimum temperature for starting seeds. Heat mats can be purchased in a variety of sizes, and the best types are those with thermostats to precisely maintain optimum temperature ranges for specific crops. After germination, young transplants generally respond well to night temperatures that are slightly cooler than daytime temperatures. Providing this temperature change can assist in producing shorter, stockier plants ready for successful transplanting. MOISTURE Maintaining appropriate moisture in the growing media is essential for proper plant growth and health. The medium should be kept slightly moist but not saturated from seeding through early growth to avoid damping off, which is the death of a seed before germination or of a young plant soon after emergence. It is caused by a group of diseases of seeds and young plants that are most damaging when the medium is kept too moist. In addition to proper watering, a challenging aspect of maintaining proper moisture conditions for young transplants is providing adequate ventilation. Maintaining gentle but consistent air movement enables growing media to slowly dry. Slow drying creates a regular need for watering and helps prevent constant saturation and disease development in 11-12

13 VEGETABLE TABLE 2 Germination, Growth, and Transplant Hardening Conditions Required for Home Vegetable Transplants APPROX. GROWING TIME (WEEKS) GERMINATION TEMP. ( F) GROWING TEMP. ( F) COOL-SEASON PLANTS CONDITIONS FOR HARDENING Broccoli, cabbage, cauliflower Lettuce 5 to 7 3 to to to 65 Over several days, introduce plants to outdoor conditions by increasing light and wind exposure. Do not immediately expose young plants to subfreezing conditions. WARM-SEASON PLANTS Cucumber, squash 2 to to 75 Over several days, introduce Eggplant 6 to 8 75 to to 75 plants to outdoor conditions by slowly increasing their exposure Pepper 7 to 9 75 to to 75 to full sunlight and wind. Reduce watering slightly, but don't allow Tomato 5 to 7 75 to to 75 the plants to wilt down. Do not expose young plants to night Watermelon, muskmelon 3 to 5 80 to to 85 temperatures below 50 or 55 F. TABLE 3 Troubleshooting Common Vegetable Transplant Production Issues COMMON PROBLEM Seedlings do not emerge Seedlings look pinched at the soil line and fall over or die (often referred to as damping off, which can be caused by more than one pathogen) Tall, spindly seedlings Older, yellow leaves POSSIBLE CAUSE(S) Seed is old or was improperly stored A pathogen-free medium was not used Medium is too wet or dry Temperature is too low or high Seed was planted too deep Overwatering that leads to poor aeration and higher disease risk Temperature is too high or low Poor ventilation (lack of air movement) Medium or containers were not sterile Light intensity is too low Nitrogen fertilization is too high Night temperature is too high Plants are too closely spaced Nitrogen fertilization is needed Plants have dried out Purple leaves Phosphorus is deficient (could be ph related) Temperature is too low 11-13

14 young seedlings. A small fan is often helpful in moving air within the seedling production area. LIGHTING Providing adequate lighting can be challenging for home transplant production. Even strong light from a south-facing window is generally not sufficient to produce healthy and stocky transplants. Higher levels of natural sunlight or supplemental lighting are often needed to produce ideal transplants. Fluorescent grow lights are common and cost-effective for smallscale transplant production. Newer technologies such as light emitting diodes (LEDs) can be good light sources for young plants, but the initial purchase price can be higher than for other lighting types. Fluorescent and LED lights produce less heat than high-intensity lights, such as metal halide or high-pressure sodium lamps. This feature simplifies home transplant production because the lights can be placed closer to the plants. A general rule of thumb is to place a fluorescent or LED light 4 to 8 inches from the plants. Closely observe the seedlings. If stems elongate and have long distances between leaves, stretching may be occurring because lights are either too high or need to be on for a longer time. (See Table 3.) Use care to purchase lights that were developed specifically for plant growth to ensure that they produce the optimum wavelengths of light. High-quality lights should provide years of safe, effective service. PLANTING AND MANAGING THE GARDEN Seeding Many crops are seeded directly into wellprepared garden soil. To ensure proper germination, it is important to understand planting times as well as rates and depth. Planting times correspond to warm- and coolseason plant classifications. Keep in mind that the seasonal differences in temperature mean that the dates given in companion resource materials are estimates, and some areas of the state may use slightly different planting times. Seeding rate must be high enough to ensure that an adequate number of plants are grown to provide a good yield, but not so high as to cause overcrowding that can reduce yield, increase management time, heighten disease risks, and waste seeds. Seeding depth is important to ensure that seeds can take up enough water to germinate and begin rooting but also emerge quickly. It is common to plant small seeds at a shallow level and larger seeds more deeply. The soil in a seedbed should be moist, crumbly, and fine so that seeds have good contact with soil particles and can quickly take up water and begin germination. (See photo on page ) A common rule of thumb is to plant seeds at a depth that is two to four times their diameter. Table 1 in the companion section provides additional information on seeding rates and depths. Transplanting Successful transplanting of seedlings depends on using quality plants that have been hardened off as previously described. It also relies on choosing a day and time when the young plants will experience the least stress. Planting on a cloudy day or during the late afternoon or evening can reduce daytime heat and light stress on the young plants. Good soil preparation and moisture content also aid the young plants. Most seedlings are placed in the garden soil at or slightly below the soil level in the current container. It is best to slightly cover the growing media with soil to prevent rapid drying and possible damage to young roots. A starter fertilizer, which is soluble and readily taken up by the young roots without the risk of salt damage, as well as consistent watering after transplanting will ease transplant stress. ph and Fertility Management Fertility and ph levels are some of the most important aspects that gardeners monitor and manage. Soil test results (see Chapter 6) should guide the fertility program, as they provide information on the current ph level and available nutrients in the soil as well as when and in what quantity the appropriate soil amendments should be applied. Gardeners 11-14

15 SOURCE: Natalie Bumgarner, University of Tennessee can apply organic matter in the fall to allow several months for it to break down before crops are planted. They may also apply lime at that time so it has time to react with the soil and have the desired effect on ph. Fertilizers are generally applied at planting time or a short time thereafter to enable plants to access nutrients and reduce the chance for leaching. INITIAL FERTILIZER APPLICATION Different vegetable crops may require slightly different amounts of specific nutrients, but the closeness of crops and the limited size of home gardens make it difficult to manage fertility for the various crops separately. For that reason, it is common for initial fertilization to be applied by the broadcast method. Soil test reports list the recommended amounts of nitrogen (N), phosphorus (P), and potassium (K) needed. Most commonly, fertilizer recommendations are listed in terms of pounds of a specific fertilizer per 1,000 square feet. Sometimes calculations are needed, so a couple simple calculations are shown as examples. (See Chapter 6.) Typically, the calculated amount of fertilizer is evenly applied to the top of the soil before planting (a process called broadcasting) and incorporated through tilling or by hand to thoroughly mix the fertilizer with the soil. It is also possible to apply the fertilizer at planting time using a method called banding, whereby a narrow band of fertilizer is applied approximately 2 inches to the side and 2 inches below the seed or seedling. This method of fertilization ensures that the soil serves as a buffer to prevent fertilizer salts from burning the seed or young plant yet keeps nutrients near young plant roots. Table 4 provides information on converting the recommended amount of fertilizer for 1,000 square feet to the amount needed for 100-foot rows if banding is preferred to broadcasting. FERTILIZATION DURING THE GROWING SEASON Garden vegetables can benefit from the addition of nutrients during the growing season. Nitrogen is the nutrient most commonly applied at that time because it is readily leached by water in the soil, but P and K can also be applied as needed. The term most often used for this fertilization method is sidedressing, which means that the fertilizer is added to the side of the row and gently incorporated. Fertilizer Newly planted radish seeds showing good contact with a fine seed bed, which is optimum for rapid germination. The seeds should be covered with approximately ¼ to ½-inch of soil and watered

16 should always be applied 6 to 8 inches from the plants to prevent salt burn. Applying water after sidedressing is also important to dissolve the fertilizer and move it into the rooting zone where it can be used. Soil tests often include recommendations for sidedressing, which can be carried out with complete or incomplete fertilizers. (See Chapter 6.) Ammonium nitrate is a common sidedressing fertilizer that adds only N, but it should be applied carefully because it can burn TABLE 4 Approximate Amount of Fertilizer to Apply to 100-foot Rows Based on Recommended Broadcast Rates from Soil Test RECOMMENDED RATE PER ACRE FROM SOIL TEST (POUNDS) CROP EQUIVALENT RATE PER 1,000 SQUARE FEET (POUNDS) leaves if it contacts them directly. Carefully follow suggestions for timing and rate because over- or under-supply of nutrients can both interfere with crop productivity. For instance, tomatoes are generally sidedressed after the first cluster of fruit has set and the young tomatoes are the size of a golf ball or slightly smaller. Young tomatoes that are supplied with too much nitrogen will produce much stem and leaf growth, which can slow or reduce fruit set and yield. EQUIVALENT FERTILIZER RATES IN POUNDS PER 100- FOOT ROW FOR VARIOUS ROW WIDTHS 18" 24" 30" 36" 48" , , Cucumbers, cantaloupe, pumpkin, squash, watermelon Tomato, eggplant, pepper TABLE 5 Recommendations for Applying Nitrogen as a Sidedressing to Garden Vegetable Crops AMMONIUM NITRATE PER 100-FT ROW AMMONIUM NITRATE PER PLANT TIMING OF APPLICATION 1 to 1½ pounds 1 tablespoon When vines are 1 foot long 1 to 1½ pounds 1 tablespoon When first fruits are 1 inch or more in diameter Sweet corn 1 to 1½ pounds -- When 12 to 18 inches tall Okra 1 to 1½ pounds -- After the first picking Lettuce 1 to 1½ pounds -- 3 to 4 weeks after seeding Turnips, spinach, collards, kale, mustard Broccoli, cabbage, cauliflower, Brussels sprouts 2 to 3 pounds -- 6 weeks after seeding 1 to 1½ pounds 1 tablespoon 3 to 4 weeks after transplanting 11-16

17 Peppers being grown using organic mulch and drip irrigation U ni ve rs ity of T en n es se e In s tru A mulch is essentially any material that covers the surface of the soil. Mulching has several benefits that include discouraging weed growth, retaining moisture, moderating temperatures, and improving soil structure. Mulches commonly used in vegetable gardens are listed in Table 6. They can be divided into two broad categories: organic and inorganic. SOURCE: Natalie Bumgarner, University of Tennessee op y ct or Mulching NATURAL OR ORGANIC MULCHES The term organic as used here describes materials that are or were at one time living; it does not refer to the term certified organic as defined by the USDA National Organics Program. Organic mulches include hay, straw, bark, wood chips, compost, and leaves as well as newspapers and cardboard. All of these materials help prevent weeds from emerging and competing with crop plants. Organic mulches are most effective in preventing annual weeds because perennial weeds can sometimes grow through such mulches. Organic mulches also add to the organic matter content of the soil as they decay. Their decomposition also saves time because it is not necessary to remove the mulch at the end of the season. An additional advantage is that organic mulches are porous and allow water to flow through to the soil, so irrigation may not be required, as it is with many plastic mulches. Use caution when incorporating bark or other woody mulch materials into the soil. Microbial processes that break down these high-carbon mulches make use of soil nutrients (especially N) and can compete with crops for C If the soil test does not provide general instructions for the rate and timing of nitrogen fertilizer applications during the growing season for specific crops, consult Table 5. Keep in mind that without soil testing, a nitrogen fertilizer application may not be effective because the soil ph or the availability of P, K, or other nutrients may be the factors limiting plant growth. It is always best to manage fertility by conducting yearly soil tests

18 the available nutrients. If left on the soil surface, organic materials break down slowly and pose less risk of disrupting uptake of soil nutrients by plants. A wider range of organic and biodegradable mulches are becoming available to home gardeners. Starch and a range of other polymers can be manufactured into sheets that can be installed and used much like plastic mulch. These products are designed to be broken down by microorganisms in the soil so that removal is not needed. Research is still under way to determine how adequately these materials control weeds and how environmental conditions affect their breakdown. INORGANIC MULCHES A range of inorganic mulches, such as black polyethylene plastic, are available for the home gardener. Black plastic mulch warms soil in the spring and suppresses most weeds if it remains intact. Clear plastic is not very useful as mulch because it allows light to pass through and can actually encourage weed growth under some conditions. White plastic generally prevents weed growth because it reflects light. Reflecting TABLE 6 Potential Benefits and Drawbacks of Common Mulching Materials for Home Gardens MATERIAL BENEFITS POTENTIAL DRAWBACKS Black plastic sheeting Woven ground cover Biodegradable mulches (manufactured) Straw or hay Sawdust or wood chips Grass clippings Compost Cost effective, preserves soil moisture, absorbs light, and retains heat May be reused, permeable to water and air Does not have to be removed, acts much like plastic mulch Biodegradable, adds organic matter, low cost Adds organic matter over time, often available free Biodegradable, adds organic matter, low cost Adds organic matter and essential nutrients solar radiation can also be beneficial under warm summer conditions in keeping the soil cooler. There are also other colors of plastic specifically designed to reflect or transmit certain wavelengths of light. Irrigation (generally of the drip type, as discussed below) is required with all of these plastic mulches. Landscape cloth, which is often woven plastic, is a good option for gardeners because it is more permeable to water. It can also sometimes be used for more than one crop rather than being thrown away after every crop, as is the case for other plastic mulches. Watering and Irrigation Soil moisture is critical for seed germination, transplant establishment, and proper plant development. Because of their rooting patterns, warm- and cool-season crops differ in their ability to tolerate low soil moisture. Cool-season crops often have shallow root systems that do not withstand the stress of water deficiency well. Warm-season crops often have deeper tap roots and are better able to survive under low water conditions. Regardless of the plant type, Must be used with irrigation, difficult to recycle, typically used for only one year More expensive, must be removed at the end of the growing season Timing of breakdown uncertain (depends on location and weather), cost may be higher Can add weed seed, keep soil cooler in early season. Be sure that no damaging residual herbicides are present on hay. Should not be incorporated with soil or it can tie up soil nitrogen Can add grass or weed seed Must be properly composted or can add seeds or disease inoculum 11-18

19 the yield and often the crop quality will be reduced if consistent watering is not maintained throughout the growing season. General estimated water needs for garden crops are 1 to 1.5 inches per week, or more for some crops under some conditions. If rainfall does not reach these levels, then supplemental watering is needed. In Tennessee, late summer and early fall are often the lowest rainfall times of year. Many crops are setting fruit and filling fruit or germinating (fall cool-season crops) during this time, so irrigation is often needed to optimize crop productivity. OVERHEAD IRRIGATION One of the most common methods of applying water to home gardens is from above the plants. Water can be applied by carrying and delivering it by hand or using a water hose. Another overhead method is the use of sprinkler systems, such as those used to water lawns. A benefit of sprinklers is their relative cost efficiency and ease of use. They can be connected to a water hose and moved to different areas of the garden as needed. Drawbacks include nonuniform water delivery and the fact that water is always applied to the leaves. Care must be taken to allow the leaves to dry before nightfall or there is an increased risk of disease. Finally, overhead irrigation often results in more water use because all crop rows and walkways are irrigated, and the water evaporates from the surfaces of both the soil and the leaves. DRIP IRRIGATION Irrigation systems that apply water slowly and steadily directly to the surface of the soil are known as drip irrigation systems. Simple drip irrigation systems can be relatively economical and work quite well for the home gardener. (See image on page ) Leaf surfaces remain dry, water is conserved by being placed directly where it is needed, and an even application can be achieved. Two similar types are commonly available. Soaker Hoses Through small perforations along the full length of the hose, soaker hoses placed on the ground alongside plants deliver water to the soil at a rate slow enough for it to soak in. These hoses are readily available and can be an easier and more efficient method of watering than overhead irrigation. A drawback is that purchasing the hundreds of feet of soaker hose needed for a large garden can be expensive, although the gardener may opt to buy a smaller number of hoses and move them to water different areas of the garden as needed. Another limitation is that soaker hoses do not always deliver water evenly because of the pressure drop along their length or uneven perforations. Trickle or Drip Tape Some of the most common drip irrigation systems are installed using drip tape. This tape is a thin-walled plastic that has embedded water emitters. The space between emitters can be varied based on soil type (closer for sandy soils), plant type, or seeding rate. Drip systems can be installed to operate automatically by using timers or they can simply be connected to a water hose when irrigation is required. SOIL WATER MANAGEMENT Managing the amount of moisture in soil is related to many other practices in the home garden. Mulching can reduce soil water loss and the need for irrigation. Maintaining proper soil moisture is also useful in making the best use of fertilizers. When the soil is dry, plant nutrient uptake is limited because most nutrients are taken up in water by the roots and move in water throughout the plant. Sidedressing and other fertilization practices are often recommended in conjunction with watering to make the nutrients more available to the plants. Conversely, excessive watering can leach the nutrients away from the plant roots and cause nutrient runoff and soil erosion. Proper water management supports both production and stewardship in the garden. Plant Maintenance PLANT SUPPORT Physically supporting certain vegetable plants (see Table 7) can help produce the best harvest for several reasons: 11-19

20 Vegetable plants that are supported can better intercept light to make sugars and optimize leaf and fruit production. Plants that are supported may be healthier because of increased air movement around the leaves and less splashing of soil particles, which can spread disease. Vegetable plants that are supported may take up less space and require less time to manage. WAYS OF SUPPORTING VEGETABLE CROPS Stakes Metal or wooden stakes can be used to support single plants. This method is common for tomatoes, peppers, eggplants, or other upright fruiting crops. Stakes can improve access to the fruit, but they also require additional time for tying each plant to the stake multiple times during the season. Stakes can also be used to form support tents or teepees, such as those often used for pole beans. Cages These structures are generally free-standing metal units designed to support tomatoes, peppers, or a range of vining bean and pea plants. While they do allow easy access to the fruit, the cage must be carefully sized to support the weight of the mature plant. Metal panels can also support vine crops. The purchase or construction of many cages or panels for the home garden may become unduly expensive. Trellises A trellis system can be constructed of wood, plastic, or twine. The general principle is to provide a flat, vertical structure or a string to support plants as they grow and bear fruit. It is most common to see trellises used for plants that have tendrils or other means to attach themselves to the trellis as they grow. Cucumbers, beans, peas, winter squash, and melons are all crops that can be trellised easily. For the larger fruited vining crops, support must also be added to the trellis to support the fruit. Clips or string can be used to attach plant stems to the trellis for plants such as tomatoes (primarily the indeterminate type, meaning that the primary growing point continues to produce leaves and flowers throughout the growing season), peppers, or other crops without tendrils. Stake-and-Twine Systems One of the most common methods of growing tomatoes commercially mostly with determinate-growth tomatoes having a compact growth habit can also be adapted for the home garden. It is essentially a combination of stakes and twine that creates a twine basket of sorts for a whole row of tomato plants by weaving twine among the plants and around the wooden or metal stakes. This system can be efficient for gardens with plant populations ranging from just a few to many. PRUNING There are several reasons for pruning vegetable plants, and the various methods serve different purposes. Pruning is more complex in perennial TABLE 7 Vegetable Crops Categorized by Their Need for Vertical Supports USE SUPPORT FOR OPTIMUM PRODUCTION AND HEALTH USE SUPPORT FOR SPACE EFFICIENCY COULD BENEFIT FROM SUPPORT DO NOT NEED SUPPORT Pole beans, snap and shell peas, tomatoes Vining cucumbers, watermelons, muskmelons, winter squash Bush beans, compact cucumber and winter squash cultivars, peppers, eggplant, okra Lettuce, beets, spinach, cabbage, broccoli, cauliflower, kale, radish, carrots, Swiss chard, summer squash 11-20

21 op y C ct or tru In s e se es SOURCE: Natalie Bumgarner, University of Tennessee en n plants (such as fruit trees) because pruning affects fruit production for years to come. In annual vegetable crops, the results of pruning are realized more quickly. rs ity of T Pruning increases light and airflow, and it can decrease the risk of disease. Pruning for these purposes is common in fruit trees and grape vines, but it can also be done for vegetables. Any damaged or diseased leaves that could spread pathogens are removed. Sometimes the lower leaves onto which contaminated soil has splashed are also removed. U ni ve Pruning can increase the quality or size of the fruit. One of the most common reasons for pruning is to manage the fruit load. This practice is common in growing tomatoes as well as some muskmelon, winter squash, or watermelon crops. If a plant is allowed to continue to set fruit without any control, there may not be enough plant sugars to support all the fruit. By carefully removing some of the fruit, that which remains can receive more support from the plant in order to reach a better size and uniform quality. One example would be heirloom tomatoes that may set more fruit than they can fill out to a nice, large size. Another example is that in growing pumpkins it may be more desirable to produce one large fruit than five smaller ones. The stake-and-twine support system (also called the Florida weave) combines wooden stakes with multiple levels of twine to support plants in a row. Pruning manages growth and can push plants to invest in fruit production. Indeterminate-growth tomatoes are one of the crops most commonly pruned for this reason. New fruit are constantly being produced while older fruit is maturing. To maintain a balance between growing new leaves and fruit and maturing older fruit, the newer branches can be removed from the plant to indirectly manage the fruit load. This is called removing suckers. Determinate tomatoes are not commonly pruned this heavily because they will produce a set number of leaves from the main growing 11-21

22 point. In these plants, fruit is produced over a shorter window of time and there is less need to prune the plant to maintain balance between leaves and fruit. Removing suckers would also reduce the overall productivity of the plant because it is limited in the number of fruit that can be produced. RAISED BED GARDENING Purposes and Benefits Some home gardeners enjoy the process of improving the soil quality and productivity on their site over time by adding organic matter through compost, cover crops, and other methods. Others, however, prefer to have another option if the soil on their site is too challenging or degraded. Raised beds are a common method used to provide a smaller, intensive growing area. They can be constructed to take advantage of the best lighting, water, and access, and they allow production to be tailored to family needs. In addition, raised beds allow more control over the growing substrate (a term used here to refer to the soil or the mineral and organic material in which plants are grown). An added benefit is that raised beds and containers can allow gardeners who are unable to handle the equipment or labor of traditional gardening to stay active and continue to produce edible crops. While there are many benefits of raised-bed production, there are also limitations: mechanical tillage equipment is difficult to use in raised beds beds must be carefully constructed to withstand the weight of substrate, plants, and management activities over time close spacing of plants can reduce airflow and increase the opportunity for disease infection or shading the growing medium drains faster and requires more frequent watering large vining squash and pumpkin plants may not be well suited to raised beds. Raised Bed Design and Construction MATERIALS Temporary raised beds using soil as the growing medium can be constructed without side supports, although these are mostly used in traditional gardens. A range of materials can be used to construct permanent raised beds including wood, stone, brick, block, or composite materials. Before December 2003, chromated copper arsenate (CCA) was used as a preservative in lumber for residential uses. Older lumber with this compound as well as railroad crossties contains metals that can leach into garden soil. Each gardener should be careful to select and use materials with which they are comfortable for their home vegetable production. See supplementary resources for more details on using treated materials. Raised beds can be lined with plastic to reduce leaching concerns, or gardeners may choose to use cedar, cypress, locust, or redwood lumber that is naturally resistant to decay. In addition, boards made from recycled plastic used for decking are a more expensive but good long-term option for constructing raised beds. It is important to select a material strong enough to construct a stable bed that can support itself plus the growing substrate and the plants. Taller and longer beds contain more substrate and thus hold more weight, so they require more substantial construction, support, and bracing. Small beds may be constructed of 1-inch-thick lumber, but it is more common to use lumber that is at least 2 inches thick. DESIGN A common bed width is 4 feet if accessed from both sides, and 2 to 3 feet if accessed from one side. Beds are generally constructed 6 to 12 inches in height but can be higher. Shallowrooted crops, such as lettuce, spinach, kale, and other leafy crops, may be produced in beds that are only 4 to 6 inches in depth. Taller and deeper-rooted crops, such as tomatoes, peppers, okra, and corn, often require deeper beds for root exploration and stability. A smaller substrate volume will retain less water. Since raised beds drain more rapidly than nearby 11-22

23 level soil, building deeper beds containing more substrate can decrease watering frequency. An additional consideration in bed design is sometimes the ability to accommodate those gardeners who are not able to work at ground level. If the site has usable soil, there may be no concern with leaving the bottom of the bed open and letting the roots of plants grow into native soil. However, hand dig or till to combine the raised bed substrate with the upper layer of native soil to avoid creating an abrupt gradient between amended and native soil. If the native soil is of poor quality or the garden is on a surface other than soil, a wooden or porous ground-cloth bottom can be installed under the raised bed. Newspapers or cardboard can also be used as a barrier to prevent weed or plant growth from underlying soil and sod, but they will be less effective if weed pressure is severe. GROWING MEDIUM If the native soil is of high quality, raised beds can be filled with topsoil from the site. If constructing a taller (12- to 24-inch) raised bed, be aware that drainage may be reduced when using only native soil. Often soilless mixes are used as a substrate to increase drainage, improve aeration, and optimize nutrition. Soilless mixes usually consist of peat moss, compost, vermiculite, and perlite. A common mix is equal volumes (not weight) of (1) peat moss, (2) compost, and (3) vermiculite. (It is best not to use older supplies of vermiculite that may be on site as they may contain asbestos.) Purchased components can also be mixed with high-quality native soil to decrease costs. A common mixture would consist of equal volumes of (1) garden soil, (2) peat moss or compost, and (3) vermiculite or perlite. Keep in mind that testing is important when preparing the substrate for a raised bed to determine if lime or fertilizer is required. If compost is used in the medium, it can provide plant nutrients, but it should still be tested to account for variations in nutritional value. Use caution when introducing any material into the medium (such as soil or compost) that could include weed seeds. If the compost has not heated sufficiently, weed seeds can still be viable. Crops and Management CROPS Many cool-season crops are quite well suited to the conditions of raised beds because of their ability to be closely spaced (see Table 8) and sequentially planted. Raised beds, because of their ease of access and higher spring soil temperatures, can often be planted earlier in the season, providing cool-season crops the opportunity to mature under preferred cooler temperatures. Warm-season crops may have deeper root depths and require more plant support and training for optimum productivity in raised beds. Beginning gardeners often make the mistake of setting plants too closely together, which creates competition for water, light, and nutrients. Even if these factors do not limit the crop, extremely close spacing can reduce air movement in the crops and increase the disease risk. Table 8 provides estimates of spacing for vegetable crops in typical raised beds. One of the benefits of raised beds is that no walking space is needed, so seeds or plants are often placed in a grid rather than rows. MANAGEMENT Irrigation Raised beds have many advantages in producing vegetables in the home garden, and many of them are linked to drainage and aeration in the growing substrate. However, it is important to remember that raised beds dry out faster than level soil. Another consideration is that closer spacing in raised beds means plant roots may not have as much soil volume to take up water. Thus water management is especially important. Typically, garden vegetables require 1 to 1½ inch of water per week. Plants in raised beds require at least this much moisture and likely more during warm or hot weather. Irrigation and watering practices as discussed above are even more important in raised beds than in traditional gardens. Drip irrigation is especially helpful in the close spacing of raised beds to keep leaves dry and prevent the spread of disease

24 TABLE 8 Vegetable Crops Categorized By Typical Spacing in Traditional Raised Beds DISTANCE BETWEEN SEEDS OR PLANTS VEGETABLES 2 to 4 inches Snap beans, beets, carrots, radishes, onions, peas, turnips, garlic, spinach, leaf lettuce, kohlrabi 6 to 8 inches Basil, Swiss chard, Bok choy, small head lettuce, strawberries, kale 12 to 18 inches Cabbage, collards, broccoli, cauliflower, eggplant, peppers, compact determinate tomatoes, compact cucumbers, and summer squash More than 18 inches Weeding, Mulching, and Rotation One of the greatest advantages of raised beds is that the reduced growing area and close plant spacing can reduce weeding chores as compared to traditional gardens. Care in selecting a substrate to avoid introducing weeds or weed seeds into raised beds can prevent future problems. Mulching can also be an excellent way to reduce weeds in raised beds. If multiple raised beds are used, it is best to rotate different types of crops in these beds, as discussed below, to reduce the buildup of pests and diseases. Support and Training Raised bed gardeners should pay special attention to plant training and support (see Table 7) to conserve space. Every inch of the raised bed is valuable growing space, and plant supports are a great way to take advantage of the entire growing area. It is common to plant vining crops (such as cucumbers, winter squash, and pole beans) on the north side of the raised bed so that a trellis can be attached to the bed to support several vining plants while reducing shading on shorter crops on the south side of the bed, as shown in the photo on page EXTENDING THE GARDENING SEASON One of the basic facts of gardening is that crops will grow, develop, and produce when conditions are appropriate. Gardeners carefully plant and manage cool- and warm-season crops so they will grow during the time of year that provides ideal temperature ranges. Managing Most summer and winter squash, watermelon, many determinate and most indeterminate tomatoes crops according to surrounding conditions can work well and fit the needs of many gardeners. However, gardeners have the option of altering the environment around their plants (the microclimate) to enable crops to be grown under a wider range of conditions, as indicated in Table 9, thus extending the season. Season extension involves exercising some control over the environment around crops (the roots, shoots, or both) to enhance productivity or maintain survival until conditions are more appropriate for growth. Certainly there are limits, but adding an extra few days or weeks to the growing season can be quite useful in vegetable gardens. The methods described here will be divided into two main groups: first, cultural management practices that can extend growing periods and second, structures or materials that can be used to alter temperatures and extend seasons. Cultural Practices that Can Extend Seasons SITE SELECTION Selecting sites to take advantage of natural microclimates is practiced, for example, when vineyards are located around lakes because temperatures in the area are moderated by the water. Examples on a smaller scale occur in plantings close to buildings that retain daytime heat, plantings that have the benefit of a windbreak to protect from cold and drying winds, and plantings on slightly sloping sites that enable cold air to drain away from the 11-24

25 SOURCE: Natalie Bumgarner, University of Tennessee plants. Over time, these areas can be identified or created around the residence, so gardeners should pay close attention to locations where microclimates can benefit the home vegetable garden. RAISED BEDS Soil temperatures can affect speed of germination as well as root growth and water and nutrient uptake, which all enhance plant growth. Raised beds have a couple of benefits in altering soil temperatures to extend seasons. In spring, water in garden soils can slow down the warming process because it takes more energy to raise the temperature of water than air. In raised beds, however, water in the soil drains more quickly, allowing warmer air to enter the soil spaces sooner and warming up the soil faster. In addition, raised beds have more surface area that can be exposed to the warming effects of the sun. However, these factors can also lead to more rapid cooling. Another benefit of raised beds is that they are well suited to accommodate other season extension practices. They can easily be fit with plastic mulches, row covers, low tunnels or even soil heating cables to warm the air and soil around plants and make earlier and later gardening possible. TRANSPLANTS One of the most common methods to extend seasons is by transplanting older plants into the garden rather than seeding them into the soil directly. (See page ) This simple practice enables plants to be grown when outdoor conditions would not allow or would slow their growth. In addition, conditions can be tailored for each type of plant, and early stresses that could limit growth can be avoided. Pest pressures may also be reduced by an early planting for some crops. Two of the most commonly transplanted crops are tomatoes and peppers because these longer-season crops can be harvested earlier when transplants are used. Also, planting can be delayed until conditions are more nearly optimal for plant growth. These warm season crops are frost sensitive, but growth can be limited by cool soil temperatures even when air temperatures remain above freezing. Raised bed with a mixture of lowgrowing bush beans and vining pole beans supported by a metal fence panel 11-25

26 Young tomato plant being grown in soilless medium in a greenhouse under optimum conditions for growth before transplantation to the garden or field SOURCE: Natalie Bumgarner, University of Tennessee Cool-season crops such as cabbage and broccoli are also good candidates for spring transplanting to reduce time to harvest and prevent them from maturing during hotter weather, which can reduce crop quality. Similarly, transplanting cool-season plants in the late summer can protect them from the warmest and driest times of the year in midsummer, reducing stress and allowing for higher quality fall-maturing crops. Conditions after transplanting influence how much time to harvest is gained by transplanting. The age of the transplant cannot always be directly subtracted from the number of days to harvest because low temperatures and lack of moisture or nutrients in soil can stress transplants after they are set out in the garden and reduce the benefits of transplanting. Temporary Methods and Structures The basis for most season extension methods involves absorbing or trapping radiation from the sun to warm up the environment around crops. For instance, dark mulches absorb light (or solar radiation) and conduct this heat to the soil below. Clear plastic covers transmit and then trap light, causing the air temperature under the covering to increase. Agricultural plastics have revolutionized season extension and provided a variety of tools that work across a range of scales, as set forth in Table 9. The biggest decision for the gardener is how much to invest in the purchase of materials and the time required to install and manage systems to alter environmental conditions. In passive systems, growers cannot increase the temperature if there is no sunlight to provide heating, although they can temporarily take advantage of heat that has been stored in the soil to provide warmth during brief cloudy periods. Also, they have only natural air movement to provide cooling. In active systems, passive heating is used, but it is combined with active heating and cooling sources to maintain more precise control, which always comes at a price. This discussion focuses on passive systems because they are the most flexible, cost efficient, and applicable for home gardeners. MULCHES Mulches can influence soil temperatures in two important ways. The first is by absorbing or reflecting incoming light. Dark mulches, such as solid black or woven plastic, absorb solar radiation and can transfer this energy to warm the soil below. Lighter mulches, such as white plastic or straw and hay mulches, reflect more light and do not warm soil temperatures as much. Under warm summer conditions, lighter mulches can be a benefit because they may keep soil temperatures lower and less variable, which can be an advantage to plants. The second way that mulches alter soil temperatures is by reducing heat loss. Heat can be lost from soil through the evaporation of water or directly by convection or radiation when air temperatures are lower than soil temperatures, as often occurs at night. Mulches, both plastic and natural, can retain heat by reducing both of these losses. Using mulches can also affect watering methods because irrigation is needed when impermeable plastic mulches are used. Natural mulches must also be carefully chosen to avoid the potential for introduction of weed seeds or herbicides. FLOATING ROW COVERS Also known as direct covers, floating row covers are usually nonwoven plastic films or agricultural fabrics that can be applied directly over crops, as shown on page These covers can be installed in large sections that 11-26

27 TABLE 9 Range of Control Over Growing Environments Provided By Various Growing Practices NO CONTROL HIGH CONTROL SOME CONTROL LOWEST COST HIGHEST COST METHOD DETAILS BENEFITS IN THE HOME VEGETABLE GARDEN Open field* Mulch* + Low tunnel or row cover* + Cold frame* + High tunnel* + Greenhouse** Crops are at the mercy of the surrounding conditions. Plastic that tightly covers soil or natural materials placed on soil surface to reduce weed growth, moderate temperatures, and conserve moisture. A thin, temporary sheet of plastic or agricultural fabric covers the crop to trap sunlight. Can be supported (typically 2 to 3 inches in height) or floating over plants. A permanent structure often made of glass or rigid plastic to trap solar radiation. Can be closed to trap heat or vented to reduce heating. A permanent plastic-covered structure that can be vented to manage temperatures. Typically large enough to walk in and unheated. A permanent structure, covered with glass or plastic, with heating and cooling to manage temperatures. Low cost Dark plastic mulch increases soil temperatures, germination, and early root growth. Organic mulches can reduce summer soil temperatures. Both can conserve soil moisture and reduce weed growth. Warm-season crops can often be planted 1 to 2 weeks earlier. Cool-season crops can be planted earlier or benefit from better early-or late-season growth. Benefit depends on whether heating is used. Transplants can be started several weeks before planting. Cool-season crops can also be grown early and late in the season. Warm-season crops can be planted from 1 to 4 weeks earlier and harvested later. Cool-season crops can often be kept alive all winter. Enables year-round growing and harvesting. * Passive using only solar energy for heating and air movement for cooling ** Active using other energy sources to heat and cool in addition to passive options + Often mulches, low tunnels or row covers, and high tunnels can be used in combination to augment benefits. cover many rows in the garden. The edges are usually secured with soil, wooden posts, or other materials. They increase air and soil temperatures by trapping sunlight. Because of their light weight and permeability, they do not need structural support. However, some crops, such as tomatoes and peppers, have tender growing points that may need protection from abrasion by floating covers. Because these covers are permeable to air and water, irrigation may not be required. Also, these covers are naturally vented because of the ability of air to move through the material. These aspects of floating row covers make them attractive to home gardeners. Additional benefits are their ability to protect plants and soil by reducing the speed of rain drop impact (reducing erosion and crusting) and the fact that they can serve as a protective barrier from insects, such as flea beetles on eggplant. Row covers are generally used as a temporary measure in spring and fall because they can trap sunlight and cause plants to overheat under warm and sunny conditions in late spring and summer. Overheating can cause leafy crops to be lower in quality and can reduce fruit set in some warm-season crops, so it is important to remove covers when the weather warms. Row covers must also be removed when crops that require pollination by insects begin 11-27

28 Floating row covers are applied over crops in a raised bed. Soil or other weights can be used to hold down the cover, or it can be secured to the raised bed itself. to flower. Often this coincides with warmer temperatures when additional heating is no longer desired. Because of the improved climate under row covers in early and late seasons, weeds can also thrive along with the crops, so proper weed control is essential. Row covers come in a variety of thicknesses that vary in their ability to increase daytime temperatures and retain heat at night. Thicker covers retain more heat but also block more incoming sunlight. It is common for gardeners to use thinner covers in the warmer seasons to retain some heat and protect crops from insects. Thicker covers are more commonly used for fall to spring cropping of cool-season vegetables where they may be installed in the late afternoon and removed in the morning. Row covers can often be reused from season to season if managed carefully and kept clean. All things considered, row covers of permeable nonwoven plastic may be the most versatile, useful, and cost-effective tool for the home gardener seeking to extend growing seasons. LOW TUNNELS Low tunnels, shown on page and in the background in the photo above, provide SOURCE: Natalie Bumgarner, University of Tennessee many of the same benefits as row covers, and sometimes the terms are used interchangeably. In this discussion, we will use the term low tunnels to describe a temporary hoop-supported structure. Often polyethylene plastics are used over these 2- to 3-foot-tall wire or plastic hoops and stretched tight to create the appearance of a miniature greenhouse. Commercial wire hoops can be purchased, or other materials, such as electrical conduit, can be used to form tunnels. These tunnels are installed along the length of a row to create a distinct air space around the crops. Low tunnels can be an asset because the larger air space around crops can provide a more consistent temperature around plants than floating covers. Also, the hoops protect sensitive crops from abrasion by the covering and from cold temperature damage caused by contact with the covering during freezing conditions. Like floating row covers, these tunnels are often removed to prevent overheating when warmer late spring and summer temperatures arrive. They also must be removed when the crop outgrows the structure or when pollinating insects need access to the crop

29 Drawbacks are that these small polyethylene tunnels can heat rapidly under bright sunlight and should be vented to prevent crop damage from overheating. Slits along the top of the tunnels (as seen in the photo below) or small perforations are common as a part of the manufacturing process. These slits reduce heat retention at night, but they lower the risk of daytime high-temperature damage. Polyethylene tunnels generally shed water, which can be a benefit in protecting crops, but as a result it is usually necessary to provide irrigation under the tunnel. Another limitation of polyethylene low tunnels is that the plastic is more difficult to reuse from season to season. It is common for plastic mulch, drip irrigation, and polyethylene low tunnels to all be installed together to achieve maximum benefit for early planting of warm-season crops. Agricultural fabrics can also be installed over hoops to form low tunnels, which can protect sensitive crop growing points or create a larger air space to retain heat. SHADE STRUCTURES Most of the season extension tools discussed so far have centered on adding and retaining heat for early- and late-season garden production. SOURCE: Natalie Bumgarner, University of Tennessee However, shade structures installed in garden areas can also extend seasons by reducing light and temperature accumulations. Benefits in Tennessee climates could include being able to harvest cool-season crops, such as leafy greens, for a longer period of time as spring temperatures rise. Additional benefits could be realized by seeding or starting fall coolseason crops earlier than normal under summer conditions. White or black shade netting can be placed over metal or plastic hoops to create shaded areas of various sizes. These commercial materials are described by how much sunlight they block and are sold in a range of percentages. To extend the growing season for cool-season crops, it is most common to use material that provides between 30 and 50 percent shade. Make sure that shade structures are well ventilated to prevent trapping heat under the netting. Permanent Structures COLD FRAMES Cold frames are familiar to many home gardeners. Often constructed of wooden frames with glass, Plexiglas, or polycarbonate Low tunnels installed in home garden plot for fall leafy crops 11-29

30 panels, these structures have long been used for transplant production. It is also common to use cold frames for early-or late-season root or leafy vegetable production. Cold frames can retain heat well when closed, and hinged lids on the boxes provide ventilation to prevent overheating on warm, sunny days. Some gardeners also set up a composting system under their cold frames to provide heating. This is often referred to as a hot bed. If the frames have access to electricity, then electric soil heating cables can be used to add heat. Limitations of cold frames are their size, accessibility, and construction expense. In addition, cold frames with hinged lids typically require close management to prevent damage to crops when bright sunlight can rapidly increase the internal temperature. Automatic opening and closing mechanisms are available as well for gardeners who are willing to invest in tools to reduce management time. HIGH TUNNELS High tunnels are more permanent, plasticcovered structures built over growing areas. They can provide warmer temperatures for crops but can also keep leaves drier and potentially reduce the incidence of foliar diseases. However, this exclusion of rainfall means that irrigation is necessary. While row covers and low tunnels are generally removed after a certain period of time, crops are usually grown in high tunnels for the entire season. The sizes of high tunnels can vary greatly from smaller structures (12 feet wide by 24 feet long) to more commercial-sized units (30 feet wide by 80 feet long). Typically, a high tunnel is tall enough for a person to work in comfortably while standing. Definitions vary, but it is common for high tunnels to be described as unheated greenhouses. This obviously limits the environmental control that can be practiced and is one of the main distinctions between high tunnels and greenhouses. High tunnels are generally constructed of wood or steel frames covered with flexible or rigid plastic. Material choices depend on cost, length of productive life, and the weather conditions of the area. Snow and wind loads are two of the most common determining factors for high tunnel design and construction. Many aspects of high tunnel design are related to the crops that will be grown in them and the seasons during which they will be used. Most high tunnels have doors and sidewalls that can be used for ventilation, while others have vents in the end walls that can provide additional air movement. Managing these methods of ventilation is one of the most time-consuming aspects of high tunnel growing. Venting, shading, and the use of multiple layers of plastic or row covers are all practices that enable more environmental control in the high tunnel. The photo on page illustrates the use of low tunnels inside a high tunnel. When these methods are combined, the growing season for cool-season crops can be extended because more heat is retained during the night. Likewise, sidewall venting, shading, or both could extend the growing season for cool-season crops in the warmer times of year. GREENHOUSES While greenhouses do use passive solar heating, the addition of active heating and often active evaporative cooling distinguishes them from other season extension practices. Because of these heating and cooling systems, the installation and operating costs of greenhouses are generally much higher than the other methods discussed here. Please refer to home and commercial greenhouse publications to learn more about the design, installation, and uses of greenhouses for home vegetable production. STEWARDSHIP PRACTICES FOR THE HOME VEGETABLE GARDEN Supporting Soil Quality The concept of long-term environmental stewardship as presented in Chapter 4 has many applications to the home vegetable garden. Two central aspects of stewardship are the connection to soil quality and nutrient management 11-30

31 SOURCE: Natalie Bumgarner, University of Tennessee the use of pest management practices to address insect and pathogen challenges. Soil health and quality are central to productivity and sustainability. In some garden sites, construction or previous site activity have degraded the soil quality. Other sites may have high-quality soils that need good management to maintain productivity. Either situation requires attention by the gardener. One of the most important things that any homeowner can do to enhance soil quality is to increase the organic matter content of the soil over time, as described in Chapter 6. This process can be a challenge in warm, moist regions because organic matter breaks down rapidly. Keep in mind that vegetable gardening is an intensive use of soil and that vegetable crops are often heavy feeders. Producing multiple crops every year leads to high nutrient use and often to frequent tillage, which can lead to reduced soil quality if not properly managed. Composting, cover crops, and appropriate management of crop residues and rotations are discussed here as methods of sustainably managing soils in the home garden. In residential gardens of any size, applying responsible management practices can benefit Tennesseans and others now and in years to come. NUTRIENT MANAGEMENT Nutrient management in the home garden should be both appropriate and intentional. Soil tests, as discussed in Chapter 6, are an excellent tool for assessing existing nutrient levels and determining whether adjustments are needed. Nutrients can be applied through the addition of organic matter, such as compost, or the use of organic and chemical fertilizers. Soil testing is important for growers who rely on any of these materials because application of unnecessary nutrients can lead to excess concentrations in the soil or to leaching of the nutrients, in addition to being a waste of time and money. Each gardener should decide which fertilizer materials he or she is comfortable using. Regardless of the specific materials selected, it is best to consider garden management methods that address both organic matter content and soil nutrients. In fact, many gardeners find that appropriate management of organic matter may over time reduce the Low tunnels can be installed within high tunnels

32 Organic material recently applied over garden soil. Be sure compost has finished decomposing before applying it to the garden. Unfinished compost will compete with plants for soil nutrients. need for added fertilizer because mineralization of organic matter produces plant-available nutrients. COMPOST Compost can be produced on site or purchased. In either case, it is best to use a source known to maintain consistent quality and to produce compost free from weed seeds, pathogens, or herbicide residues that could damage crops. Not all composts are equal, so monitor or inquire about the materials used to produce the compost. Whether home-composted or purchased, only stable compost should be added to the garden before planting, as shown below. Refer to the Chapter 6 companion digital section for more complete instructions on home composting. Also keep in mind that increasing the organic matter in soil is ideally accomplished over time. Materials that contribute organic matter also contribute nutrients, potentially in excess. For instance, high phosphorus levels can result from repeated applications of some compost materials, so soil tests should be used to monitor nutrient changes over time. Nutrients can be leached from compost if they are available in larger quantities than needed by plants. In addition to increasing the possibility of losing nutrients to the environment, excessive levels of some nutrients can create issues in the uptake of other nutrients. CROP RESIDUES Plant residues remaining after harvest are a significant source of organic material. These residues can be left on the soil surface as mulch, composted, or incorporated into the soil. These options all have positive and negative aspects. Leaving plant residues on the surface protects the soil from erosion and supports earthworm populations. However, pests and disease pathogens can overwinter in the debris, so pest survival can often be reduced by incorporating the residues into the soil. Nonetheless, turning crop residues under also causes them to break down faster, which may speed nutrient release. Quicker release of nutrients could mean that SOURCE: Natalie Bumgarner, University of Tennessee 11-32

33 they are less available later in the growing season when most needed by plants. Also consider that it may be best to remove crop debris entirely if disease levels were high in the crop during the growing season. When deciding whether to incorporate residues, consider both the need to protect the soil surface (and whether cover crops will be used) and the potential for pest and disease impacts. COVER CROPPING The term cover crop refers to any living plant that acts as a ground cover and can provide many benefits. (See Chapter 6, Table 2.) Cover crops can be used in the garden in three main ways. The first and most common is as a green manure. This means that the cover crop is sown, allowed to grow, and then killed by tilling it into the soil. This practice adds nutrients and organic matter to the soil as the plants break down. Green manures can be winter cover crops or a summer cover between a spring and fall crop. The second way to use a cover crop is as living mulch grown with the main crop. These SOURCE: Natalie Bumgarner, University of Tennessee living mulches, such as white clover, can block weed growth, reduce erosion and over time add organic matter to the soil. Crop species to be grown as living mulch must be carefully selected so they will not detrimentally compete with the main crop for water and nutrients. A third way that cover crops can be used in the garden is as a killed mulch. This means that a cover crop is sown and grown much in the same way as a green manure. However, instead of killing and tilling it into the soil, the plants are killed and left on the soil surface as mulch. In this manner, organic matter can be slowly added to the soil while reducing weed growth and protecting the soil surface from erosion. See the digital companion section for additional information. Supporting Plant Health and Productivity CULTIVAR SELECTION The use of resistant cultivars is one of the most effective tools available to home gardeners A cover crop grown over the winter in a raised bed to provide organic matter 11-33