Plants annual or perennial. Taproots slender to stout, sometimes absent; perennials often with stout, branched caudices, some with adventitious roots from decumbent stems or elongating rhizomes. Stems erect, ± sprawling, or less often decumbent or prostrate, usually branched, terete. Leaves briefly connate proximally, sessile; blade 1- or 3–5-veined, linear to oblong or ovate, apex rounded or obtuse to acuminate. Inflorescences dichasial cymes or thyrses, diffuse (to subcapitate in G. oldhamiana); bracts paired, proximal bracts foliaceous, distal ones smaller, herbaceous with scarious margins; involucel bracteoles absent. Pedicels erect in fruit. Flowers: sepals connate proximally into cup, 1–5 mm, cup green and white, 5-veined, not winged, obconic to campanulate, terete to 5-angled, commissures between sepals veinless, broad, scarious; lobes green at least along midrib, usually ovate to elliptic, equaling or longer than cup, margins white, scarious, apex rounded to obtuse, sometimes mucronate; petals 5, white, pink, or rose-purple, claw poorly differentiated, auricles absent, coronal appendages absent; blade apex entire or shallowly emarginate to 2-fid, nectaries at filament bases; stamens 10, arising with petals from low nectariferous disc; filaments distinct nearly to base; staminodes absent; ovary 1-locular; styles 2(–3), clavate, 1.2–2.5 mm, glabrous proximally; stigmas 2(–3), subterminal, papillate (30×). Capsules globose or ellipsoid-ovoid, opening by 4(–6) slightly distally recurving valves; carpophore absent. Seeds 4–36, brown to black, reniform to snail-shell-shaped, laterally compressed, tuberculate, marginal wing absent, appendages absent; embryo peripheral, curved. x = 17, 12 (Eurasia), 18 (Eurasia); aneuploidy occasional.