Herbs or subshrubs, annual or perennial, densely pubescent or glabrous, rhizomatous. Stems ascending, decumbent, or prostrate, herbaceous or suffrutescent, usually bearing buds at base in perennial species. Leaves: distal leaves opposite, proximal leaves sometimes alternate, sessile or petiolate; blade lanceolate to circular, chartaceous to fleshy, base attenuate, cuneate, cordate, or oblique, margins entire, apex acute to obtuse. Inflorescences axillary, sessile dichasium, subtended by 2 subopposite, involucral leaves that become indurate and connate in age. Flowers bisexual, sessile or short-pedicellate; tepals 5, distinct, keeled, inner 2 distinctly shorter than outer 3, scarious or coriaceous, base cuneate, margins entire or distally crenate, apex acute or obtuse [aristate], glabrous or lanuginose; trichomes completely and partially candelabriform or with random projections [barbed]; stamens 5; filaments connate at base into low cups, usually equal; anthers 2-locular; pseudostaminodes triangular short lobes [linear, equalling filaments] or absent; staminodes present or absent; ovule 1, membranous; styles absent or short; stigmas 2-fid or seldom irregularly 3-fid (in var. oblongifolia), deltoid. Utricules subglobose, proximally membranous, distally hyaline, indehiscent. Seeds 1, brown-red or white, obovoid. x = 10.
|[For Ivar T. Tidestrom, 1864-1956, Swedish-born American botanist noted for floras of central and western United States]|