The daisy or Compositae family is so large—950 genera, 20,000 species and even more cultivated varieties and hybrids—that you could fill hundreds of gardens with family members without even thinking about plants from outside the clan. Over the last three decades or so, individual daisy genera, including coneflower, asters, Shasta daisies and blanketflower, have caught the eyes of plant breeders, resulting in an avalanche of new introductions.
Coreopsis, or tickseed as it is known to its oldest friends, is one of those daisy genera that has bedazzled plant breeders in the U.S. as well as Europe. As the result, the plant-buying public is now so spoiled for coreopsis choice that confusion inevitably results.
It all started with a gang of between 50 and 100 annual and perennial species native to the Americas. The flowers of all coreopsis have the conventional daisy configuration—flowerheads composed of a round or disk-shaped centers housing the tiny true flowers, surrounded by long petals or rays in shades of golden yellow, white or rose. The flowerheads may be quite small—less than one inch across—or larger, at up to two and a half inches in diameter. The green leaves range from thread-like to lobed or dissected. Coreopsis plants may be up to about four feet tall, but some hybrids and varieties are considerably smaller.
Before all the hybridizing started, home gardeners grew only a few perennial species and varieties. Large-flowered coreopsis—Coreopsis grandiflora—grows up to two feet tall on slender stems, bearing golden yellow flowers and slender oblong leaves. Newer grandiflora varieties, like ‘Early Sunrise’ boast fluffy double flowers. Coreopsis grandiflora is very similar to another coreopsis often used in breeding, lance-leaf or Coreopsis lanceolata. Versatile thread-leaf coreopsis—Coreopsis verticillata—can grow even taller and also bears yellow flowers. The leaves are slender green filaments. Thread-leaf coreopsis is quite amenable to breeding efforts and new verticillata varieties abound. Coreopsis rosea features pink daisies. The rosea species is most likely responsible for the introduction of the pink/red coloring now present in many coreopsis varieties. Like their daisy-family relatives, the common coreopsis types are very attractive to butterflies and other pollinators.
The big news in coreopsis is the same as the big news in other flowering species—wider color range, compact forms that fit better in containers or small spaces, increased hardiness and more flowers more often. This last feature is especially important, as many modern gardeners want perennials that perform like traditional bedding annuals, providing near constant bloom from spring through frost.
Massachusetts-based breeder Darrell Probst grew up within shouting distance of the fabled Longwood Gardens in Pennsylvania. His work with coreopsis is characteristic of modern breeding efforts. Famed for hybridizing ground-covering epimediums as well as coreopsis, Probst created the Big Bang coreopsis series, including burgundy and yellow ‘Cosmic Eye’, yellow-flowered ‘Full Moon’ and deep red ‘Mercury Rising’. All are medium height—18 to 24 inches tall—with large, colorful flowers and a repeat-blooming habit. Because the hybrids are sterile, they do not set seed, so there will be no offspring, wanted or unwanted. The sterile trait also means that deadheading is not needed to stimulate further flower production.
Another big American coreopsis vendor is Terra Nova Nurseries, a company that has long aimed to increase the color quotient—both from foliage and flowers—in gardens and containers. Terra Nova’s coreopsis introductions frequently feature a mounding habit that makes them good ground cover or container subjects. The company has developed annual coreopsis, like the compact Lemonade Series, with stems that rise to 8 inches tall and bear hot-colored blooms. The foliage is gold-tinged. Among Terra Nova’s perennial offerings are the low-growing Jewel Collection, which also tops out at eight to nine inches tall and bears warm-colored flowers. Earlier generations of pink or red coreopsis varieties were not really hardy in cold-winter climates. Newer introductions in the pink-red-orange range are more reliably cold tolerant.
The European and Japanese share a love affair with native American plants and have also produced new coreopsis varieties and hybrids. Like its relative, goldenrod, tickseed has become a world plant.
Coreopsis is easy to grow and not fussy about soil type. Most species, varieties and hybrids are at their best and produce abundant flowers in full sun, though the vendors often like to broaden the appeal by specifying “part to full sun.” If you plant in the shade, make sure it is very light shade. Once established, most coreopsis are at least somewhat drought tolerant as well.
Most well-stocked plant merchandisers have an array of coreopsis on display this spring. For Terra Nova retailers, use the search tool available at http://www.terranovanurseries.com/gardeners/retail_sources.php. Find a good coreopsis selection, including some Darrell Probst varieties at White Flower Farm, P.O. Box 50, Route 63 ~ Litchfield, Connecticut 06759 , (800) 420-2852, www.whiteflowerfarm.com. Free catalog.