Perennials, 60-210 cm (rhizoma-tous, forming colonies). Stems erect to ascending, striate, glabrous, gland-dotted, resinous. Leaves present at flowering; short-petiolate; blades (1- or 3-nerved, larger prominently 3-nerved) lanceolate, 50-130 × 8-30 mm, bases tapered to petioles, margins entire or finely dentate, apices acute to acuminate, faces glabrous, black gland-dotted. Heads in dense, terminal, flat-topped, corymbiform arrays. Involucres hemispheric; staminate 3.5-5 mm, pistillate 3.8-4.8(-6) mm. Phyllaries narrowly lanceolate, 2-4 mm, inner series ± equal, margins yellowish, medians green to purplish, apices acuminate, erose or ciliate, faces glabrous, gland-dotted, resinous. Staminate florets 26-40; corollas 3.5-4 mm. Pistillate florets 80-150; corollas 1.7-3 mm. Cypselae 0.6-1.5 mm, 5-nerved, glandular, hispidulous distally; pappi 2.6-4(-7) mm. 2n = 18.

Flowering Jul-Oct (all year). Moist salt marshes, coastal strands, stream edges, hillsides, railroads; 0-1200 m; Calif., Oreg.; Mexico (Baja California).

Occurring along the coast and in interior valleys, Baccharis douglasii is recognized by the erect, simple stems growing in patches from rhizomes, large lanceolate leaves with three veins and blackish glandular dots, heads in dense, compact, terminal, corymbiform arrays and more or less uniform inner phyllaries. G. L. Nesom (1990h) noted that it is similar to forms of the South American species Baccharis pingraea de Candolle, and that the two taxa may be conspecific.