Approximately 300 species of annuals, perennials and subshrubs of almost worldwide distribution. They have opposite pairs of usually simple leaves and tubular two-lipped, hooded flowers from the upper leaf axils, or forming terminal spikes or racemes.
Several of the small mountain species are desirable rock garden and raised bed plants, and make attractive pan specimens for the alpine house. Well drained but not dry soil is needed and a site in sun, though a little shade is tolerated. Propagated by division in autumn or spring or seed in spring in a cold frame.