Rock Rose is a charming, low growing perennial that blooms late spring to early summer. Simple five-petaled flowers come in shades of red, apricot, orange, yellow, pink, rose, and white. Plants are 6 or so inches high and spread to 18 inches. Leaves are green to grey-green and are finely textured. Unlike some spring bloomers, Rock Rose has very nice summer foliage, making it an good choice for a groundcover, though one that doesn't receive foot traffic.
Grow in well drained soil and full sun to part shade. Deadheading isn't necessary, but cutting the whole plant back by a third in mid summer can result in more dense foliage and, sometimes, a second blooming in the fall, though it will be less showy. In mild winters, foliage may be evergreen, but summer sun may score the leaves; evergreen boughs are useful as a protective cover. There are helianthemum planted at the Washington Square Conservation Garden.