Asthmaweed

Conyza bonariensis is widespread in tropical and warm-temperate regions of the world. It is thought to be native to South America.

Plants erect, 10–100(–150+) cm, branched mostly distally. Leaves: faces ± densely strigose or hispidulous; proximal blades oblanceolate, 30–80(–120+) × 10–25+ mm, obscurely lobed to coarsely toothed or entire; distal narrowly oblanceolate to linear, 10–50 × 2–10 mm, obscurely toothed or entire. Heads usually in paniculiform to racemiform, rarely corymbiform arrays. Involucres 3.5–5 mm. Phyllaries usually strigose or hispidulous; outer greenish to purplish, lanceolate, shorter; inner stramineous to purplish, linear-attenuate (more chartaceous to scarious, less hairy). Receptacles 3–5 mm diam. in fruit. Pistillate florets 60–150+; corollas ± equaling or surpassing styles, laminae 0 or to 0.3 mm. Disc florets 8–12+. Cypselae pale tan, 1–1.5 mm, faces glabrous or sparsely strigillose; pappi of 15–25+, pinkish, sordid, or tawny bristles 3–4+ mm. 2n = 54.

A pantropic weed of American origin.

1400-2800 m

Erigeron bonariensis Linnaeus, Sp. Pl. 2: 863. 1753