Over 400 species of shrubs, trees, perennials and annuals from the temperate regions of both hemispheres and tropical mountains. They have simple leaves in opposite pairs or rarely three to four whorled and generally yellow five-petalled flowers with a large central tuft or three to five bundles of very slender stamens.
All the small species described are worthy of cultivation on the rock garden and some, notably H. olympicum and cerastioides, have long been included in lists of recommended beginners' alpines. Well drained ordinary soil and a sunny site are necessary for most species, but some require more moisture. Propagation by seed or division in spring or cuttings in late summer.