About 60 species of annuals, perennials and shrubs from U.S.A. and Mexico. They have alternate, usually pinnately lobed leaves covered with minutely barbed hairs and terminal clusters of flowers with five spreading petals and a prominent boss of stamens. In some species, the outer stamens are petallike, even lacking anthers, in others, the filaments are flattened with teeth-like flanges or lobes.
Several species are just about small enough for the larger rock garden but they resent winter wet and are short-lived and look rather out of place in the alpine house. Freely draining but ordinary soil and plenty of sun are required. Propagation by seeds in situ or sown in containers and planted out with a minimum of root disturbance.