in W. H. Emory, Not. Milit. Reconn., 140. 1848.
Plants erect, 20–60 dm. Stems erect to spreading; bark distinctively cinnamon-colored, papery-layered; young stem internodes yellowish green, 1.5–7 (–15) mm (marked with slender paired decurrent grooves), finely hirtellous, sessile-glandular. Leaves on slender long-shoots, proximal 1–2 opposite, distal subalternate or alternate; stipules absent; blade yellow-green, linear to terete, (2.5–) 5–14 (–26) × 0.4–0.6 (–0.8) mm, apex recurved-apiculate, surfaces sparsely hirtellous and sessile-glandular. Inflorescences paniculate or reduced to spicate racemes (terminating all distal, long-shoots of season), 0.8–5 (–7.5) cm, hirtellous; subtending flower bracts linear-subulate; bracteoles 5 or 6, outermost subulate, inner oblong-ovate, concave. Pedicels present or absent. Flowers in sessile clusters of 2–3 (or single and pedicellate); hypanthium greenish, 0.6–2 mm, hirtellous, inner rims yellowish; sepals broadly ovate, 0.6–1 mm; petals persistent, whitish, turning rusty brown, elliptic to ovate, 1.5–2.2 mm; stamens 10 (–12), filaments 1–1.5 mm, anthers 0.4–0.6 mm; ovaries obliquely obovoid; styles erect, pinkish, 0.5–1 mm. Achenes ellipsoid, 1.1–1.6 mm, exserted from hypanthium. 2n = 18.
Phenology: Flowering Jul–Aug(–Sep).
Habitat: Dry granitic slopes, mesas, ravines, chaparral, pinyon woodlands
Elevation: 200–2000 m
Calif., Mexico (Baja California)
Adenostoma sparsifolium is known in southern California from San Luis Obispo and Santa Barbara to Riverside and San Diego counties, and in northern Baja California.