Plants robust. Flowering stems simple, 20-55 cm. Leaves in basal rosette and cauline, basal leaves 3-5-lobed, cauline (1-3), deeply 3-lobed, usually reduced, similar to basal; stipules narrow, not decurrent on petiole base, (margins fimbriate); petiole to 22 cm; blade dark green, orbiculate to reniform, (base cordate), surfaces variously hairy. Inflorescences 1-9(-15), (often lax), nodding racemes, simple, 3-9(-15)-flowered, (10-60 cm). Pedicels equaling or shorter than hypanthium. Flowers deciduous if unfertilized, not fragrant, horizontal; hypanthium obconic, elongating in fruit, throat constricted or partially open, (length 2 times diam.); sepals erect, often remaining slightly erect in fruit, triangular; petals (exserted), not widely spreading, white with obscure venation, ovate-elliptic, narrowly clawed, usually shallowly 3-lobed, rarely unlobed, (sinuses extending to 1/2 distance to base), 4-13 mm, ultimate margins entire, sometimes with extra tooth, (lobes acute); ovary ± completely inferior; styles included in fruit; stigma papillae in narrow subapical, sometimes apical bands. Seeds 0.5-0.6 mm, smooth, sometimes rough. 2n = 14, 21, 28, 35.
Flowering Mar-May. Coastal mountains, open, well-drained, grassy slopes, clearings, open bluffs in oak or coniferous-oak woodlands, sometimes in semishade or coastal north-facing canyons; 0-2000 m; Calif., Oreg.
Flowering in Lithophragma affine is dependent upon sufficient rainfall. Often-abundant vegetative reproduction is by aerial or subterranean bulbils. The southern California specimens form a polymorphic complex related to the topography of the region, seasonal precipitation, and reproductive biology. The north-coastal distribution is complicated by introgression with L. parviflorum. Similar transitional forms occur in central coastal California to the Sierra Nevada foothills.
The Mendocino Indians used the root of Lithophragma affine to treat colds and stomach aches (D. E. Moerman 1998).