Univ. Calif. Publ. Bot. 40: 63. 1966.
Annuals, to 30 cm. Stems erect, usually branched proximally, sometimes distally, villous. Leaves linear to linear-oblong, 10–80 × 1–5.5 mm, margins usually entire, sometimes 1–2-toothed (teeth to 2 mm), faces hairy. Heads showy. Involucres campanulate to obconic, 5–7 mm. Phyllaries 5, obovate to ovate, slightly hairy. Receptacles subulate, papillate, glabrous. Ray-florets 5–10; (corollas yellow or white) laminae broadly elliptic to oblong, 3–5 mm. Disc corolla lobes 5. Anther appendages deltate (with 1–4 wartlike glands; style apices ± deltate with apical tufts of hairs and subapical fringes of shorter hairs). Cypselae black, ± linear, to 3 mm, hairy; pappi 0, or of 2–4 brown or white, ovate or lanceolate, aristate scales. 2n = 8.
Phenology: Flowering Mar–May.
Habitat: Shaded or open, moist woodland slopes
Elevation: 0–500 m
Lasthenia debilis is inconspicuous and has pale green foliage and lightly pigmented, relatively short rays. Populations with white or nearly white rays, uncharacteristic for lasthenias, are known.