Ageratina thyrsiflora
Ageratina lemmonii
congested snakeroot
Lemmon's snakeroot
erect (usually forming compact ‘bushlets’), finely and evenly puberulent (hairs minute, bent).
(commonly purple) erect, puberulous (hairs usually with colored crosswalls).
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.
opposite;
petioles usually 0, sometimes 1–2 mm;
blades ovate-lanceolate, 2–4.5 × 0.5–2.5 cm, margins shallowly serrate, abaxial faces glabrous or glabrate, gland-dotted.
3–8 mm, puberulent.
10–60 mm, puberulent.
2.5–3 mm.
4–5.5 mm.
white (orange-veined), glabrous.
white, lobes densely hispid-villous.
apices acute to obtuse (dark orange-veined), abaxial faces.
(narrowly oblong-lanceolate) apices acute, abaxial faces sparsely hairy to glabrate.
clustered (in dense, terminal aggregates).
in loose, open arrays.
hispid.
sparsely and finely hispidulous.
= 34.
Ageratina thyrsiflora
Ageratina lemmonii
Ageratina thyrsiflora is known from the United States from a single collection dated 1929 from “near Nogales” in Santa Cruz County. It is recognized by its strict, unbranched or few-branched stems with alternate, densely arranged leaves, relatively small heads densely clustered in terminal aggregates, orange-veined phyllaries and corollas, and closely puberulent stems and petioles (hairs minute, sharply upwardly bent).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
WildflowerSearch
iNaturalist
USDA Plants Database
