Ageratina adenophora (Spreng.) R. King & H. Rob.

Subshrubs, 50–220 cm. Stems (usually purplish when young) erect, stipitate-glandular. Leaves opposite; petioles 10–25 mm; blades (abaxially purple) ovate-lanceolate or ovate-deltate to lanceolate-ovate, (1.5–)2.5–5.5(–8) × 1.5–4(–6) cm, bases cuneate to obtuse or nearly truncate, margins serrate, apices acute to acuminate, abaxial faces stipitate- to sessile-glandular. Heads clustered. Peduncles 5–12 mm, densely stipitate-glandular and sometimes also sparsely viscid-puberulent. Involucres 3.5–4 mm. Phyllaries: apices acute, abaxial faces stipitate-glandular. Corollas white, pink-tinged, lobes sparsely hispidulous. Cypselae glabrous. 2n = 51.

Eupatorium adenophorum Sprengel, Syst. Veg. 3: 420. 1826, based on E. glandulosum Kunth in A. von Humboldt et al., Nov. Gen. Sp. 4(fol.): 96, plate 346. 1818; 4(qto.): 122, plate 346. 1820, not Michaux 1803