Ageratina thyrsiflora

Perennials or subshrubs, 50-100 cm. Stems erect (usually forming compact `bushlets´), finely and evenly puberulent (hairs minute, bent). Leaves usually alternate, sometimes subopposite (densely overlapping internodes); petioles 3-20 mm; blades ovate-lanceolate to triangular, 2.5-6.5 × 1-2.5(-3) cm, bases obtuse to cuneate, margins shallowly and coarsely crenate to serrate to subentire, apices rounded-obtuse, abaxial faces hirtellous. Heads clustered (in dense, terminal aggregates). Peduncles 3-8 mm, puberulent. Involucres 2.5-3 mm. Phyllaries: apices acute to obtuse (dark orange-veined), abaxial faces. Corollas white (orange-veined), glabrous. Cypselae hispid.

Flowering Sep-Nov. Rocky sites, oak woodland; 1000-2200 m; Ariz.; Mexico (Chihuahua, Durango, Jalisco, Sinaloa, Sonora).