Conyza canadensis
Canadian fleabane, Canadian horseweed, horseweed, vergerette du Canada
faces usually glabrate (proximal margins ± ciliolate, hairs usually stiff, spreading and hispid on nerves, hairs erect);
proximal blades oblanceolate to linear, 20–50(–100+) × 4–10(–15+) mm, toothed to entire;
distal similar, smaller, entire.
3–4 mm.
1–1.5(–3) mm diam. in fruit.
20–30(–45+);
corollas ± equaling or surpassing styles, laminae 0.3–1 mm.
8–30+.
usually glabrous, sometimes sparsely strigose (margins chartaceous to scarious);
outer greenish to stramineous, lanceolate to linear, shorter;
inner stramineous to reddish, lance-attenuate to linear.
usually in paniculiform, sometimes corymbiform arrays.
uniformly pale tan to light gray-brown, 1–1.5 mm, faces sparsely strigillose;
pappi of 15–25, white bristles 2–3 mm.
= 18.
Conyza canadensis
Conyza canadensis is thought to be native to North America and is now widely adventive, e.g., in South America, Europe, Asia, and Africa. Plants with stems glabrous and phyllaries red-tipped are sometimes treated as var. pusilla; similar plants with stems glabrous and phyllaries stramineous (not red-tipped) are sometimes treated as var. glabrata.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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