Coreopsis verticillata at Kingwood Center, Mansfield, Ohio

Coreopsis ‘Jethro Tull’ (photo from ItSaul Plants, Inc.)

Threadleaf coreopsis (Coreopsis verticillata), also called tickseed, is a popular summer flowering  perennial. Coreopsis are native to the U.S. and produces hundreds of pale-yellow blooms. Depending on cultivar, plant grows 12 to 18 inches tall and 2 feet wide. Some gardeners even plant old-time favorites like ‘Zagreb’ and ‘Moonbeam’ as annuals (USDA hardiness zones 4 – 9).

Big flower tickseed (C. grandiflora) produces larger flowers on taller plants, up to 3 feet high. Flowers are bright yellow and daisy-like. Many cultivars re-bloom a second and even third time if mowed back after a bloom cycle has finished. They tolerate hot, humid summers, but garden soil should not be allowed to dry out. Height and spread vary by cultivar and level of care (irrigation + fertilizer).

Coreopsis are one of the easiest perennials to grow. For best show plant 3 or more of one cultivar for a sea of color in a sunny front garden border or in containers. Set out plants anytime from late April through September. Plant 12 to 18 inches apart in a sunny spot and in well-drained soil. Plant the crown just at or above the soil surface.

Removing spent flowers encourage re-blooming, prevents reseeding, and gives the flower bed a neater look. Yellow to gold flowers attract numerous nectar seeking bees and butterflies. Leaving the seedpods on plants will attract large numbers of goldfinches.

Divide clumps every 3 years for optimum plant performance. Aphids may be occasionally pests. Powdery and downy mildew on foliage in garden areas with poor air circulation; some cultivars are rated better for mildew resistance.

Recent Coreopsis Introductions:
‘Cosmic Eye’-  daisy blooms with wine-red petals, tipped in soft yellow and surrounding an orangey yellow button eye; grows 18 inch high by 24 inch wide. Introduced by Darrell Probst and is reliably hardy in zones 4 – 9 with winter snow cover.

‘Jethro Tull’ – compact grower, 18 inches high by 24 inches wide with dark-green leaves and blanketed with single golden-yellow daisies with a ring of tubular petals; hybrid introduced by ItSaul Plants in Georgia.

‘Mercury Rising’ – another Darryl Probst introduction large velvety-wine daisy flowers with contrasting gold-orange button center, appearing in succession from mid summer to mid autumn. Some flowers may appear frosted in creamy-white. Cut plants by half in mid-July if plants begin to flop. (hardy in zones 4 – 9 with winter snow cover).

‘Route 66’ – threadleaf coreopsis discovered in 2005 in a Pennsylvania garden; plants grow 24-28 inches tall with bright yellow petals with large red eye; long blooming period from late June until mid October.