Coreopsis verticillata, commonly called threadleaf coreopsis or whorled coreopsis, is a rhizomatous perennial which typically grows in dense, bushy clumps to 1-3' tall. Features yellow, daisy-like flowers (1-2" diameter) with yellow untoothed rays and yellow center disks. Flowers appear singly in loose clusters (cymes) in a profuse and lengthy late spring to late summer bloom. Shearing plants in mid-summer will promote a fall rebloom. Palmately 3-parted leaves with thread-like segments lend a fine-textured and airy appearance to the plant.The genus name comes from the Greek words koris meaning bug and opsis meaning like in reference to the shape of the seed which resembles a bug or tick.Specific epithet means having whorls in reference to the leaves.Plants in the genus Coreopsis are sometimes commonly called tickseed in reference to the resemblance of the seeds to ticks.'Zagreb' is more compact (to 1.5' tall) and features bright yellow, daisy-like flowers (1-2" diameter) with untoothed rays and darker yellow center disks.