Shrubs, 15-450 cm (prostrate and mat-forming to erect and rounded, much branched). Stems spreading to ascending, dark brown, shiny, striate-angular, glabrous, often ± scurfy, usually resinous and sticky. Leaves present at flowering; sessile or short-petiolate; blades (1- or 3-nerved) oblanceolate to obovate, the smaller 5-40 × 2-15 mm (thick), bases cuneate, margins entire or coarsely dentate (teeth 3-9 distal to middles), faces glabrous, gland-dotted, resinous. Heads (100-200+) in (leafy) paniculiform arrays. Involucres hemispheric to campanulate; staminate 3.2-5 mm, pistillate 3-6 mm. Phyllaries ovate to lanceolate, 1-3 mm, margins yellowish, scarious, medians yellow proximally, green distally, apices obtuse to acute or acuminate (erose, abaxial faces papillose-scurfy). Staminate florets 20-34, 3-4 mm. Pistillate florets 19-43; corollas 2.5-3.5 mm. Cypselae 1-2 mm, 8-10-nerved, glabrous; pappi 6-9 mm.
Baccharis pilularis can be distinguished by its dark brown stems, and serrate, obovate to oblanceolate leaves. In addition, plants from some dunes of the California coast are prostrate, a growth form unique to this genus in our region.
The common, weedy, widespread form is subsp. consanguinea, which is typically erect, with its larger leaves 15-40 mm. Subspecies pilularis is known only from exposed sandy dunes and bluffs along the central coast of California. Its growth habit is matlike, and its larger leaves are 5-15 mm. The prostrate habit of subsp. pilularis is strikingly different from the upright habit of subsp. consanguinea.