The “Flower Tower’ flowers expand up to 2 1/2 inches across and often bloom from August into September. (Photo by Ginny Rosenkranz)

Coreopsis is a wonderful native herbaceous perennial that comes up out of the ground every spring, has dark green foliage and beautiful bright daisy-like yellow flowers in the summer.
Like all plants, Coreopsis has a common name, Tick Seed, but it does not attract ticks into the garden, it just has seeds that can look like ticks.
All Coreopsis are very late to emerge from the cold ground in the spring, they like to wait until the ground warms up before venturing into the garden.
It is always a great idea to trim down the frost-killed tops to about 1-2 inches off the ground in the late fall to remember where they were so new spring plants aren’t planted on top of the late-emerging Coreopsis.
The only problem with Coreopsis was that some of the species did not live past the required three years that could name them “perennials.”
We have a wonderful Botanical Arboretum, Mt. Cuba Center, located in Hockessin, Del. which does a lot of research on many of our native perennials including the cheerful flowers of Coreopsis.
The center trialed 13 different coreopsis species and the related cultivars and hybrid to check for their growing habits, the flowering display, any diseases that might attack them and best of all, how long they will live in the garden.
They found that the cultivars of Coreopsis were able to thrive for many years in full sun, well drained soils, and tolerant of both heat and high humidity making them perfect for all the sunny gardens on the Eastern Shore.
The Coreopsis with the highest ratings was Coreopsis palustrsis “Summer Sunshine.”
It had very vigorous mounds of deep green foliage that stayed lush and green all growing season and grew up to 30 inches tall.
The flowers explode into color in late September and create a wave of yellow gold petals that surround a dark brown cone.
“Summer Sunshine” blooms for up to 6 long wonderful weeks which give the gardens lots of color and provides the pollinators a long term banquet.
This beautiful cultivar spreads slowly by underground rhizomes and has proved to be the most disease-resistant Coreopsis of all that were trialed.
Another lovely addition to the summer gardens is Coreopsis tripteris “Flower Tower” that can grow up to 8 feet tall.
This strong stemmed plant can provide a wonderful and colorful background for perennial gardens or even a summer hedge.
The dark yellow gold flowers expand up to 2 1/2 inches across and usually bloom from August into September.
It also spreads slowly by rhizomatous roots and can thrives in poor to sandy well drained soils. Coreopsis tripteris “Gold Standard” also grows tall in the summer garden, reaching a sturdy height up to 5 feet.
“Gold Standard” starts blooming in late July and will continue to bloom for two months with bright yellow petals surrounding the center dark brown cone.
Flowers also bloom on secondary shorter growth which allows the plants to have flowers almost all through the plants.
This cultivar is also very resistant to many of the leaf diseases that the native species succumbs to including powdery mildew, downy mildew, and leaf spot.
Another variety of Coreopsis is the Thread leaf or Coreopsis verticillata.
C. verticillata “Moonbeam” was the first Coreopsis that survived in the garden for decades instead of years, and was the inspiration of many plant growers to create new, longer living, disease resistant varieties and cultivars.
Coreopsis verticillata “Zagreb” is a sturdy plant growing only 20 inches tall that in from May to June is completely covered with tiny yellow dark gold flowers with a darker gold center disk.
The leaves are arranged on the plant in a whorled fashion and are very thin giving the plant a breezy airy look.
The flowers bloom on the tops of the plants creating a floating carpet of color.
“Zagreb” spreads by rhizomes and in moist, fertile soils it can self seed.
Another fall blooming cultivar is Coreopsis integrifolia “Last Dance,” which bursts into bloom with 2-inch bright gold flowers in September through October.
Plants slowly grow up to 2 feet and provide their deep green foliage through the summer until they flood the garden with color in the fall.
There is a lovely hybrid, Coreopsis verticillata “Golden Gain” with parents of C. verticillata and C. verticillata “Zagreb” which combines the compact, sturdy structure of “Zagreb” at the base of the plant and the breezy airy structure of the species.
Coreopsis verticillata “Golden Gain” has both more and larger bright yellow gold flowers than either of its parents, blooming with color from late spring to late summer gardens.
(Editor’s Note: Ginny Rosenkranz is a commercial horticulture specialist with the University of Maryland Extension.)