Plants 0.2-0.5 dm, often with 1-3+ simple, ascending branches; hypocotyl 0.3-1.5 cm. Stems 2-5-noded. Leaf blades to 0.4-0.7 × 0.4 cm. Cymes 1-branched, 2-10-flowered, 1-2 cm. Flowers 3-4 mm diam.; calyx base tapering to pedicel; petals first ascending, soon erect, separated, later appressed to utricles, yellowish becoming pale, closely red-lineolate except margins, narrowly lanceolate or arcuate, 2.5-3.5 × 0.5-0.9 mm, apex subacuminate; stamens 5; pistils 1.5-2 mm, subglabrous; styles erect, 0.2-0.4 mm. Utricles ascending, 2-2.5 mm. Seeds 1-1.3 mm. 2n = 18.

Flowering spring. Dry vernal pools and clay flats; of conservation concern; 500-700 m; Calif.

The utricles of Sedella leiocarpa have a conspicuous ventral flange 0.2 mm wide. The plants grow in dense colonies; the species is very local, thus far found in only two places, south of Clear Lake, Lake County.