Annuals, 8-100(-150) cm. Stems ± erect. Leaves mostly cauline; proximal opposite, most alternate; ± sessile; blades narrowly elliptic to linear or (proximal) oblanceolate to spatulate, margins usually entire (proximal sometimes toothed), faces hirsute to strigose, sericeous, or villous (all or distal sometimes stipitate-glandular as well). Heads radiate, in ± paniculiform arrays or in glomerules. Peduncular bracts: pit-glands, tack-glands, and/or spines 0. Involucres ± hemi-spheric or obovoid to obconic, 3-6+ mm diam. (sometimes subtended by calyculi of 2-5 bractlets). Phyllaries 5 in 1 series (linear to oblanceolate, herbaceous, each wholly enveloping a subtended ray ovary, abaxially piloso-hirsute to hirtellous or scabrellous). Receptacles flat to convex, densely hirtellous, paleate (paleae in rings between rays and discs, distinct or proximally connate, scarious). Ray florets 5, pistillate, fertile; corollas yellow (often nerved with red to purple abaxially). Disc florets 6, functionally staminate; corollas yellow, tubes shorter than funnelform throats, lobes 5, deltate (anthers ± dark purple; styles glabrous proximal to branches). Ray cypselae ± obcompressed (attachments basal, apices beakless, faces glabrous); pappi 0. Disc cypselae 0; pappi 0. x = 7.

Molecular phylogenetic data have indicated that Lagophylla is sister to Layia (S. Carlquist et al. 2003). Members of Lagophylla are easily overlooked in the field; leaves usually wither before flowering and heads often close at midday. Ray laminae often shrivel greatly in pressed specimens (making lengths difficult to assess). The species are moderately interfertile (W. C. Thompson 1983); most do not co-occur and no natural hybrids have been documented.