Annual Coreopsis for the Mid-Atlantic Region

Transcription

1 Annual Coreopsis for the Mid-Atlantic Region George Coombs, Assistant Research Horticulturist Annual coreopsis, or tickseed, is undergoing a period of rediscovery by American gardeners. Once a widely cultivated wildflower, annual coreopsis fell out of favor long ago as the design of modern gardens became more intentional and organized. However, new breeding efforts are bringing annual coreopsis back into today s mainstream gardens as bedding and container plants. Many of these new cultivars have been hybridized from two species, Coreopsis tinctoria and Coreopsis rosea, to produce plants that are compact, floriferous and bloom in numerous colors and patterns. In 2012, Mt. Cuba Center initiated a trial of 27 cultivars of annual coreopsis. Our goal was to evaluate the horticultural and ecological potential that this new group of plants has to offer. Top performing plants were selected based on their habit, floral display and disease resistance. With the addition of seven new cultivars released since our trial began, it is clear that the rise in popularity of annual coreopsis is just beginning. Clockwise from top left: Coreopsis Fruit Punch, C. tinctoria Mahogany Midget, C. Pumpkin Pie, and C. Cha Cha Cha.

2 Coreopsis tinctoria, commonly known as golden tickseed or plains coreopsis, is the species people find most familiar. The yellow-and-red bicolor flowers can be found throughout the continental United States. Originally native to the Great Plains and southern United States, Coreopsis tinctoria has escaped cultivation and naturalized throughout much of the eastern U.S. Coreopsis rosea, also known as small rose tickseed, is a perennial species native to the southeastern United States and has been used by plant breeders to introduce varying shades of pink to annual coreopsis flowers. Recent breeding efforts have led to a multitude of colors, including red, orange, pink, white and nearly every shade in between. Breeders have turned annual coreopsis from tall, wispy wildflowers with fleeting blossoms into compact blooming machines that provide bright color all summer long. Top-rated Plants After evaluating 27 cultivars of annual coreopsis for two seasons, five selections stood above the rest for their outstanding garden performance. What follows is a description of the top-rated cultivars and the reasons for their ratings. Also mentioned are four cultivars of the Lemonade Series that scored lower than the top-rated selections but have sufficiently interesting foliage that may justify their inclusion in some gardens. See the chart on page 6 for detailed performance information on each of the cultivars in the trial. Coreopsis Salsa Coreopsis Salsa was consistently noted for its extremely floriferous display of yellowand-red bicolor flowers. The compact 15 tall plants are upright and bushy and begin flowering earlier than most other cultivars. Salsa starts blooming in May and continues through August. It reaches its peak floral display in early June and maintains a tremendous number of flowers throughout the remainder of its bloom period. These flowers differ from the similarly colored Cha Cha Cha in that the central red portion of the flower is much larger on Salsa. Powdery mildew was barely a concern with Salsa, having only observed the disease three times over the entire two-year trial. Coreopsis Jive Coreopsis Jive is similar to Salsa with a compact, upright and well-branched habit. This cultivar stood out as being the most resistant to powdery mildew of any in our trial. Powdery mildew was observed on this plant only once during the entire two-year period. Jive is a fantastic selection because the eye-catching white-and-red bicolor flowers create an attractive display that grabs your attention long before you approach the plants. The flowers are slightly larger than one inch in diameter and have a dark red central core with brilliant white outer petals. Jive is an early flowering cultivar with a bloom period that is nearly identical to Salsa. Page 2

3 Coreopsis RP #1 (Little Penny) Coreopsis Pineapple Pie Coreopsis RP #1, commonly sold as Little Penny, has an incredibly compact habit. Measuring only 10 tall and wide, Little Penny was the smallest cultivar in our trial. The terra cotta flowers are also petite, measuring only ¼ of an inch in diameter. The plants were so uniform in shape and densely packed with flowers that they almost looked artificial. Little Penny would make a fabulous container plant for the patio or deck. Coreopsis Pineapple Pie rated very highly because of its ability to maintain a dense and upright habit with healthy foliage for the entire summer. The floral display was also excellent, although it was not as impressive as Salsa, Jive or RP #1 (Little Penny). This cultivar reached its peak display in late June but continued to delight with bright yellow flowers with cherry-red s until the very end of summer. Powdery mildew resistance also proved to be one of the best in the trial. Coreopsis verticillata Golden Dream Coreopsis verticillata Golden Dream was one of the standout performers in our trial because of its lush green foliage and excellent habit throughout the entire summer. Being more similar to the perennial Coreopsis verticillata types, the floral display was never as impressive as some of the other annuals. However, what it lacks in flower quantity, Golden Dream makes up with its healthy late season foliage. The sunshine yellow flowers measure one inch in diameter and begin to appear in late June. They reach their peak display in mid-july and continue to provide cheerful color well into September. Page 3

4 Special Mention- Lemonade Series The Lemonade Series deserves a special mention because even though they were not the top performing plants in our trial, they do have the added benefit of several weeks of ornamental foliage before flowering begins. There are four cultivars in this series: Cherry Lemonade, Pink Lemonade, Strawberry Lemonade and Tropical Lemonade. Each has electrifying chartreuse foliage and flowers in red, pink, fuchsia, or orange. Coreopsis Cherry Lemonade Chartreuse foliage in early May. Coreopsis Tropical Lemonade What is Powdery Mildew? Powdery mildew is a fungal disease that appears as a whitish fuzz or haze on the leaves and stems of many different plants. This fungus is ubiquitous in the environment and requires only proper weather conditions to develop. Powdery mildew develops in periods of warm, dry weather and does not require high humidity to initiate an infection. The humid conditions most people associate with the development of powdery mildew are only required for the formation of spores which allow the fungus to spread to nearby plants. However, once the spores have contacted susceptible foliage, the disease can develop quickly in humid or dry weather. While powdery mildew is usually only a cosmetic nuisance, severe cases can cause defoliation. Nothing that extreme was observed on any of the annual coreopsis. In 2013, the worst incidence of powdery mildew was an infection spanning 6 weeks; however, the worst incidence in 2012 lasted 15 weeks. The extremely wet weather in 2013 likely reduced the disease pressure because the fungal spores cannot survive in freestanding water. Three cultivars, Coreopsis Jive, Salsa, and RP #1 (Little Penny), stood out for being exceptionally resistant to powdery mildew. Page 4

5 Weather Impacts In 2013, nearly all of the cultivars finished their lifecycle approximately three weeks earlier than they did in One possible explanation was the extremely wet soil throughout much of the summer set a record for the most rainfall ever recorded in the month of June with 12.5 inches. To put that in perspective, 12 inches of rain is typically what we would receive over the course of the entire summer. Coreopsis are notorious for requiring well-drained soil, and while no deaths were caused by the extremely wet weather, the added stress likely contributed to their early decline. Month Avg. Temp. High/Low ( F) Historical Avg. Temp. High/Low ( F) Monthly Precipitation Total (inches) Historical Avg. Precip. (inches) May 76/56 72/51 76/ June 81/58 81/61 85/ July 88/67 86/68 88/ August 85/64 80/62 87/ September 76/56 75/52 80/ and 2013 data provided by DEOS weather station at Mt. Cuba Center. Historical data provided by the National Weather Service for Wilmington, DE ( ). Plants for Pollinators One reason annual coreopsis merit a place in our gardens and landscapes is for the ecological benefits they can provide. Throughout the two-year period we made weekly observations of whether pollinators were present on each cultivar. Every cultivar we trialed was observed to support various insects with the exception of Coreopsis tinctoria Roulette. The absence of observed pollinators on this cultivar is likely a result of its few and fleeting flowers rather than any inherent inability to support pollinating insects. In 2013, we tasked our intern, Bethany Troy, to collect and identify the pollinators and other insects visiting four different cultivars of annual coreopsis. The four cultivars were chosen as representatives of the various flower colors found among the group. Over a period of three weeks, more than 200 insects representing 29 different species were collected and identified. More information about this project is available on our website. The incredible variety of pollinators found on annual coreopsis demonstrates the potential benefits a garden or landscape can provide to the local wildlife. Bright yellow pollen adheres to one of the pollinators. Mt. Cuba Center has recently partnered with researchers at the University of Delaware to further explore how cultivar selection and hybridization affect plant-pollinator interactions. Bethany Troy collecting pollinators. Page 5

6 Plant Characteristics and Performance Summary Ratings COREOPSIS RATING AVG. H x W C. 'Cha Cha Cha' " x 14" FLOWER COLOR yellow with red FLOWER SIZE BLOOM PERIOD WEEKS OF POWDERY MILDEW OVER 2 YRS SERIES 1.5" late May - late Aug. 12 Coloropsis C. 'Cherry Lemonade' " x 14" red.75" mid-june - early Sept. 14 Lemonade C. 'Cherry Pie' " x 14" red 1" mid-june - mid-aug. 8 Pie C. 'Fruit Punch' " x 16" C. 'Garnet' " x 20" C. 'Jive' " x 12" light pink with dark pink pink with dark pink white with red 1.25" mid-june - mid-sept. 5 Punch 1.25" late June - early Sept. 8 Hardy Jewel 1.25" late May - late Sept. 1 Coloropsis C. 'Limbo' " x 18" white 1.25" mid-june - late Sept. 9 Coloropsis C. 'Limerock Dream' " x 18" pinkish-orange 1.25" mid-june - early Sept. 18 C. 'Limerock Passion' " x 18" pink 0.75" late June - early Sept. 14 C. 'Limerock Ruby' " x 18" pinkish-red 1.25" mid-june - early Sept. 13 C. 'Mambo' " x 16" C. 'Pineapple Pie' " x 12" light pink with dark pink yellow with red 1.25" late May - late Aug. 9 Coloropsis.75" mid-june - mid-sept. 5 Pie C. 'Pink Lemonade' " x 14" pink.75" mid-june - early Sept. 12 Lemonade C. 'Pumpkin Pie' " x 14" orange 1" mid-june - late Aug. 4 Pie C. rosea 'Tahitian Sunset' " x 18" pinkish-orange 1.25" mid-june - early Sept. 13 C. 'RP #1' (Little Penny) " x 10" terra cotta.25" mid-june - early Sept. 4 Pie C. 'RP #4' (Lemon Punch ) " x 16" yellow 1" late June - late Aug. 19 Punch C. 'RP #5' (Mango Punch ) " x 16" orange 1" late June - early Sept. 9 Punch C. 'Rum Punch' " x 18" pinkish-orange 1.25" mid-june - late Sept. 14 Punch C. 'Salsa' " x 14" yellow with red 1.5" mid-may - late Sept. 3 Coloropsis C. 'Strawberry Lemonade' " x 14" dark pink 1" mid-june - early Sept. 12 Lemonade C. 'Strawberry Punch' " x 18" pinkish-red 1" late June - early Sept. 15 Punch C. 'Summer Punch' " x 20" gold with red 1.75" early June - mid-sept. 5 Punch C. tinctoria 'Mahogany Midget' " x 12" red 1.25" early June 5 C. tinctoria 'Roulette' " x 14" red with smaller yellow petals 1.25" mid-july - mid-aug. 0 C. 'Tropical Lemonade' " x 14" orange 1" mid-june - early Sept. 14 Lemonade C. verticillata 'Golden Dream' " x 16" yellow 1" late June - mid-sept. 12 Ratings: 5 = Excellent, 4 = Good, 3 = Fair, 2 = Poor, 1 = Very Poor More About the Trial The evaluation took place at Mt. Cuba Center, located near Wilmington, DE (USDA Hardiness Zone 7a/6b). Twenty-seven cultivars of annual coreopsis were trialed over a two-year period ( ). These plants were evaluated weekly to assess the following horticultural attributes: bloom time, flower coverage, habit, disease and pest resistance, and adaptability to environmental conditions. Each cultivar was grown in a block of ten plants arranged in two rows of five with plants spaced on one foot s. They were grown in full sun in a clay-loam soil with a ph around 6.5. Each cultivar was measured weekly and assigned a rating based on a 1-5 scale. Floral display was also recorded based on the percentage of the mass that was covered in flowers. Additionally, observations were made for the presence of disease, particularly powdery mildew, as well as any visiting pollinators. Each cultivar was planted from 1-qt. size pots in early May. Supplemental water was given as needed only during the first month to promote establishment, and no fertilizer was provided outside of the original starter charge used in growing the plants. Pesticides and fungicides were not used. The plants were removed as they began to wane in September 2012, and replanted in the same manner the following year. Page 6

7 Coreopsis Cha Cha Cha Coreopsis Cherry Lemonade Coreopsis Cherry Pie Coreopsis Fruit Punch Coreopsis Garnet Coreopsis Jive Coreopsis Limbo Coreopsis Limerock Dream Coreopsis Limerock Passion Coreopsis Limerock Ruby Coreopsis Mambo Coreopsis Pineapple Pie Coreopsis Pink Lemonade Coreopsis Pumpkin Pie Coreopsis rosea Tahitian Sunset Coreopsis RP #1 (Little Penny) Coreopsis RP #4 (Lemon Punch ) Coreopsis RP #5 (Mango Punch ) Coreopsis Rum Punch Coreopsis Salsa Coreopsis Strawberry Lemonade Coreopsis Strawberry Punch Coreopsis Summer Punch Coreopsis tinctoria Mahogany Midget Coreopsis tinctoria Roulette Coreopsis Tropical Lemonade Coreopsis verticillata Golden Dream Page 7

8 Tips for Getting the Most From Your Annual Coreopsis Siting Coreopsis are best planted in gardens or containers that receive a minimum of 6 hours of direct sunlight. They also prefer moist but well-drained soil. These conditions are easily met in any large container, but moist, well-drained soil can be hard to find in the average garden. An easy trick to create well-drained soil in areas with heavy clay is to incorporate a 4-6 inch layer of compost into the existing soil, helping create a bed that is slightly higher than the area around it. This simple technique can mean all the difference when dealing with plants that require good drainage. Even though moist soil is preferred, annual coreopsis can go several days without supplemental water. So if you re heading out of town for the weekend, you don t need to fret about your coreopsis. Coreopsis are great in containers. Uses Annual coreopsis pair perfectly with sun loving perennials like summer phlox (Phlox paniculata), coneflowers (Echinacea spp.), butterfly weed (Asclepias tuberosa), bee balm (Monarda spp.) and their cultivars. Containers are also a great option for patios and balconies. Deadheading Deadheading annual coreopsis provided little benefit when weighed against the time required. We evaluated two methods: complete shearing and individual removal of spent flowers. Shearing was the quickest and most efficient method, but the complete removal of spent and developing flowers left the plants without blooms for approximately three weeks, during what would have otherwise been a period of peak display. The second method, individual deadheading, did allow for the continuous production of new flowers, but was very time consuming. Both of these methods extended the period of bloom for many cultivars by a couple of weeks, but neither method warrants the required sacrifices. Shearing annual coreopsis greatly reduces the floral display for at least three weeks. Fertilizer We were slightly disappointed with the late season appearance of many of the annual coreopsis in our evaluation. Other trial locations that provide regular water and fertilizer observed plants to be much healthier in late summer/early fall. The addition of fertilizer, particularly late in the season, may help to delay their decline and provide a longer period of display. Conclusion As a group, annual coreopsis were not overly impressive when compared to more traditional annuals like geraniums or petunias. Many selections did not provide sufficient color from spring until frost. However, cultivars like Salsa, Jive, Pineapple Pie, RP #1 (Little Penny), and Golden Dream stood out from the crowd because of their excellent habit, floral display and disease resistance. Their vibrant blooms and ability to attract a multitude of pollinators are sure to bring color and joy to any garden or patio. References Armitage, A. M. Herbaceous perennial plants: A treatise on their identification, culture, and garden attributes. 3rd ed. Champaign, IL: Stipes, Coreopsis tinctoria. Missouri Botanical Garden Plant Finder. Missouri Botanical Garden. 04 Feb < DEOS Historical Monthly Station Summary Retrieval. Delaware Environmental Observing System. 10 Feb < Klett, D., D. Staats, and K. Christ Annual Flower Trial Garden Performance Report. Annual Flower Trial Garden at Colorado State University Feb < NOWData - NOAA Online Weather Data. National Weather Service Forecast Office. 10 Feb < Trial Flower Gardens. - Penn State Variety Trials. 04 Feb < Troy, B. Observing Pollinators on Annual Coreopsis. 04 Oct Mt. Cuba Center. 04 Feb < Page 8