Annuals, 5-40 cm. Stems erect. Leaves mostly cauline; proximal opposite, distal alternate; sessile; blades linear, margins entire or toothed, faces usually hirsute, sometimes minutely stipitate-glandular as well (glands usually black, sometimes yellowish). Heads radiate, borne singly or in loose, ± umbelliform to corymbiform arrays. Peduncular bracts: pit-glands, tack-glands, and spines 0. Involucres obovoid to obconic, 2-5+ mm diam. Phyllaries 3-8 in 1 series (lanceolate to oblanceolate, herbaceous, strongly conduplicate, each wholly enveloping a ray ovary). Receptacles flat to convex, glabrous or setulose, paleate (paleae falling, in 1 series between rays and discs, distinct or weakly connate, phyllary-like, more scarious). Ray florets usually 3-8, pistillate, fertile; corollas bright yellow (laminae flabelliform to obovate). Disc florets 7-30, bisexual and fertile or functionally staminate (sometimes in same head); corollas bright yellow, tubes shorter than narrowly funnelform throats, lobes 5, deltate (anthers yellowish to brownish; styles glabrous proximal to branches). Ray cypselae (black) terete to ± compressed, weakly arcuate, gibbous or not, beaked or beakless, glabrous; pappi 0 or of 3-12 lanceolate to subulate, fimbrillate to plumose scales. Disc cypselae (black) ± terete, ± clavate, glabrous or hairy; pappi of 7-11 lance-attenuate, linear, oblong, quadrate, or subulate, fimbriate, fimbrillate, or plumose scales. x = 9.

Members of Harmonia occur in mountains of northwestern California, as far south as the northern San Francisco Bay area. All but H. nutans are known only from serpentine exposures and are probably descended from a common, serpentine-endemic ancestor (B. G. Baldwin 2001). Harmonia has been treated in Madia, which is more closely related to Carlquistia than to Harmonia (B. G. Baldwin 1996). See Baldwin (2001) for discussion of phylogeny within Harmonia.