Plants spreading, decumbent, prostrate, or rarely slightly erect, 0.3-1(-1.5) × 0.5-2(-10) dm, villous. Leaves basal; petiole 0.2-1.8(-2) cm; blade oblanceolate, 0.3-2 × 0.1-0.4 cm, villous. Inflorescences rather dense with secondary branches suppressed, white to greenish; bracts 2, similar to leaf blades at proximal nodes only reduced, short-petiolate, becoming linear and aciculate at distal nodes, acerose, 0.3-2 cm × 1-4 mm, awns absent. Involucres 1, mostly greenish, cylindric, not ventricose, 2-2.5 mm, with thin to broad and then conspicuous white or pinkish to purple, scarious margins extending nearly full length of awn, not corrugate, villous-hirsute; teeth spreading to divergent, equal, 0.5-1 mm, awns uncinate with longer ones 1-2 mm, anterior one mostly 2 mm, alternating with shorter (0.5-1 mm) ones. Flowers exserted; perianth bicolored with floral tube lemon-yellow and tepals white, campanulate, 2.5-3 mm, glabrous; tepals connate ca. 1/ 3 their length, monomorphic, oblong, acute to obtuse and entire apically; stamens 3-9, slightly exserted; filaments distinct, 1.5-2 mm, glabrous; anthers yellow, oval, 0.3-0.4 mm. Achenes dark brown, globose-lenticular, 2-2.5 mm. 2n = 38, 40, 42. Flowering Apr-Jul. Sandy to gravelly flats and slopes, coastal scrub communities, pine-oak woodlands; 30-800 m; Calif. The involucral margins of Chorizanthe diffusa vary greatly. In some individuals, the white margins are barely visible. Plants with the margins of the involucre are predominantly white have been designated var. nivea. A full gradation between the extremes may be observed in most populations, although in coastal sands var. nivea is often the dominant expression. Diffuse spineflower occurs near the coast and in the Coast Ranges of central California.
Chorizanthe diffusa has been shown to inhibit carcinogen-induced preneoplastic lesions in a mouse mammary-organ culture model. This inhibitory activity is known to correlate with cancer chemopreventive effects in full-term models of tumorigenesis (see H. S. Chung et al. 1999).