North of California, northwards to south Washington, and eastwards to Utah
Open, rocky locations in chaparral and coniferous forests; up to 12,000 feet
Triangular, up to 2 inches long, stalked, with irregularly serrate edges
Ageratina occidentalis grows in mountainous locations, in the north half of California and parts of most of the northern states. Stems (woody at the base) grow mostly upwards, and bear broad, triangular leaves at quite closely-spaced intervals, oppositely arranged near the ground and alternate higher up. Stems are light green in color, often with purplish blotches.
The inflorescence is a branched cluster of narrow flowerheads that contain disc florets only; typically ten per head. Florets are about half an inch long, mostly pale pink but darker at the base, and they open to five tiny lobes. Several stamens project well beyond the lobes. At the base of the flowers is a ring of equal-length phyllaries, covered by very fine, short hairs, sometimes glandular.