Thread-leaved coreopsis is very easy to grow. It is drought tolerant and grows well in sandy soils, but it fares less well in heavy, wet ones. Feed with a low-nitrogen plant food immediately after the first flush of flowers has been cut back. Divide after 2 to 3 years. Propagate by rooting summer cuttings taken from nonflowering stems (see page 118).
Thread-leaved coreopsis is noted for its yellow (but sometimes pink) flowers that appear in prodigious quantities all summer. It is indispensable in the garden and looks its best planted in sweeps of ten or more (you simply can’t have too many). Its colors blend well with every other color in the rainbow, and the foliage is neat and tidy. Thread-leaved coreopsis is a thoroughly well-behaved perennial, deserving of a reputation as one of the world’s great garden plants. It has one minor flaw: a tendency to spread a little too freely in climates that remain warm and moist all summer.
Without qualification, thread-leaved coreopsis belongs in every perennial bed or mixed border; it is that good. It adds lots of color to plantings of ornamental grasses, especially those that give their main show in fall when they blossom. Although it blooms most heavily in full sun, in the South coreopsis needs light shade. It’s also useful as a ground cover since its dense habit will choke out all but the most persistent of weeds. Coreopsis adds consistent color to shrub plantings, most of which bloom in spring. It’s nearly impossible to plant it with a color with which it clashes.
ZONES: 3–9
BLOOM TIME: Midsummer until frost
LIGHT: Full sun in the North; light shade in the South
HEIGHT: 24–36 inches
INTEREST: Lacy green foliage topped with myriad bright yellow flowers