Crofton weed

Ageratina adenophora

Erect, branched herb with glandular and simple multicellular hairs, 1–2 m high, with a short rootstock.

Leaves triangular to rhombic, 4–12 cm long, 3–9 cm wide, apex acute to acuminate, base broad-cuneate, margins crenate to toothed, lamina dark green, slightly hairy or glabrous, veins prominent and hairy; petiole to 4 cm long.

Heads 5–8 mm diam., crowded in corymbs; involucral bracts narrow-lanceolate, 2-seriate, ± equal, glandular, striate, green to reddish. Florets white.

Achenes 1–2 mm long, glabrous; pappus bristles 3–4 mm long, barbellate.