Overview and Description
Coreopsis are native American prairie and woodland plants. Their ruggedness and profuse blooms have made them popular with plant breeders and there are over 100 different species available, although not all are perennial plants. Low maintenance, drought tolerant and long blooming, Coreopsis are workhorses in a sunny flower border. Their common name, "tickseed," is supposedly for the seeds' resemblance to ticks.
That doesn't stop the birds from devouring them if you leave the seed heads on during the winter. Goldfinches, in particular, enjoy Coreopsis seeds.
Most Coreopsis are clump forming, holding their daisy-like flowers on tall stems, above the foliage. There the similarity ends. There is a good amount of variety among Coreopsis species. C. grandiflora has bright yellow flowers on tall stems that bloom all summer. C. rosea has finely textured leaves with pink daisy-like flowers with yellow centers. The increasingly popular C. verticillata is called the thread leaf coreopsis because of its extremely fine and ferny leaves. The flowers are also delicate and profuse. A red C. verticillata has recently been introduced.
Hardiness will vary with species and cultivar and not all Coreopsis varieties are perennial plants. Many of the newer varieties are still be tested for hardiness and their ratings may change.
But in general, most of the perennial coreopsis are hardy in USDA Hardiness Zones: 4-9.
Plant size will vary with species, age, and growing conditions, but most correopsis grow somewhere between 10--18 inches tall with a spread of about 12--24 inches. They tend to grow in clumps, but many varieties will self-sow throughout your garden.
Coreopsis will bloom best in full sun, but it can also be successfully grown in partial shade. The plants may get a bit lankier in partial shade, but they will adapt. In areas with intense dry, heat, coreopsis may even prefer some afternoon shade.
Most varieties will start blooming in early summer and repeat bloom periodically through to fall. Deadheading the spent flowers will encourage more blooms.
- C. grandiflora 'Early Sunrise' - Large, semi-double bright yellow flowers starting in early summer (12--24")
- C. grandiflora 'Golden Showers' - profuse cheery yellow blooms on long stems. (18--36")
- C. verticillata 'Moonbeam - buttery yellow flowers, extremely airy. (12--18")
- C. verticillata 'Zagreb' - Golden yellow flowers. Dependable (12--18"')
- C. rosea 'Nana' - Mauve-pink, dwarf variety that spreads nicely (8")
Coreopsis work well in any type of border. Because of their long bloom time, they make great fillers. Coreopsis grandiflora has a strong tendency to self-seed and makes a great choice for cottage type gardens.
The thread-leaf varieties soften both bold leaved plants and hard edges and add airy movement to gardens, but they tend to be short-lived. The yellows blend beautifully with the purples and blues of iris, liatris and salvia 'Victoria'.
Most coreopsis varieties are very easy to grow and are not particular about soil quality or soil pH. Many can be grown from seed, either started indoors, 4-6 weeks before your last expected frost, or direct seeded outdoors. As mentioned, many will seed themselves; however, the hybrid varieties do not grow true to seed.
Coreopsis will need regular water when first planted until they are established. After that, they are quite drought tolerant.
Deadheading will keep the plants blooming throughout the summer. Some of the smaller flowered varieties are difficult to deadhead and you may prefer to shear the plants, once the first flush of flowers fade. They will fill in quickly.
Most coreopsis plants will form tidy clumps, but some of the taller species may require staking to look attractive, especially if grown in partial shade.
Although they are rugged plants, they don't tend to live more than 3 to 5 years. A decrease in flowering is a signal it is time to divide the plants or plant some new ones from seed.
Pests and Problems:
For the most part, coreopsis grow problem free. In damp seasons they many fall prey to snails and slugs and fungal diseases can affect them. To avoid these problems as much as possible, give them plenty of air circulation and plant them in full sun.