Ageratina rothrockii

(A. Gray) R. M. King & H. Robinson

Phytologia 19: 216. 1970

Common names: Rothrock’s snakeroot
Basionyms: Eupatorium rothrockii A. Gray in A. Gray et al., Syn. Fl. N. Amer. 1(2): 102. 1884
Treatment appears in FNA Volume 21. Treatment on page 550. Mentioned on page 548.
Perennials, (20–)40–70(–150) cm (slender, fibrous-rooted crowns, with slender rhizomes). Stems ascending to erect, puberulent to glabrate. Leaves opposite; petioles 2–20 mm; blades (3–5-nerved) lanceolate to lanceolate-ovate, mostly 3–6 × (1.5–)2–3 cm, bases obtuse to truncate, margins serrate to crenate, apices acute to acuminate, sparsely puberulent abaxially, mostly along nerves. Heads clustered. Peduncles 5–12(–20) mm, puberulent. Involucres 5–7 mm. Phyllaries: apices acute, abaxial faces glabrous or glabrescent, eglandular. Corollas white, lobes short-villous. Cypselae sparsely and finely strigose-hirsute. 2n = 85 [ca. 100, fide A. M. Powell on label].

Phenology: Flowering (Jul–)Aug–Oct.
Habitat: Rocky slopes and ledges, in oak-juniper, pine-oak, pine, aspen, and spruce-fir woodland
Elevation: 1700–2400 m



Ariz., N.Mex., Tex., Mexico (Chihuahua, Coahuila, Durango, Sonora).


Ageratina rothrockii is similar to A. altissima, probably its western vicariant, and the two perhaps would be justifiably treated as conspecific.



Lower Taxa

No lower taxa listed.