Ageratina rothrockii
Ageratina
Rothrock's snakeroot
snakeroot
ascending to erect, puberulent to glabrate.
usually erect, rarely scandent, sparsely to densely branched.
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.
cauline; mostly opposite (distal sometimes alternate); petiolate;
blades 3(–5)-nerved from bases, usually deltate, lanceolate, ovate, rhombic, or triangular, sometimes orbiculate, margins entire, crenate, dentate, or serrate, faces glabrous or hispidulous, pilose, or puberulent, sometimes gland-dotted (A. occidentalis, A. adenophora).
5–12(–20) mm, puberulent.
5–7 mm.
campanulate, 3–6 mm diam.
convex (glabrous or hairy), epaleate.
10–60;
corollas white or lavender, throats obconic to campanulate (lengths 1.5–2 times diams.);
styles: bases sometimes enlarged, glabrous, branches linear, seldom distally dilated.
white, lobes short-villous.
apices acute, abaxial faces glabrous or glabrescent, eglandular.
persistent, 8–30 in 2(–3) series, 0- or 2-nerved, lanceolate to linear, ± equal (herbaceous).
clustered.
discoid, usually in compact, (terminal and axillary) corymbiform arrays, sometimes borne singly.
sparsely and finely strigose-hirsute.
prismatic or ± fusiform, usually 5-ribbed, scabrellous and/or gland-dotted;
pappi usually persistent, sometimes fragile, rarely falling, of 5–40, barbellulate bristles in 1 series.
on label].
= 17.
= 85 [ca. 100, fide A. M.
Ageratina rothrockii
Ageratina
Ageratina rothrockii is similar to A. altissima, probably its western vicariant, and the two perhaps would be justifiably treated as conspecific.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Species ca. 250 (14 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Shrubs | → 2 |
1. Perennials or subshrubs | → 3 |
2. Petioles (2–)3–5 mm; leaf blades 1–2 cm, margins entire or shallowly crenate, facesgland-dotted | A. wrightii |
2. Petioles 3–10(–15) mm; leaf blades (2–)3–5(–7) cm, margins coarsely crenate, facesnot gland-dotted | A. havanensis |
3. Leaves alternate on at least distal 1/4–1/2 of stems | → 4 |
3. Leaves opposite | → 6 |
4. Heads usually borne singly (rarely 2s or 3s); involucres 11–12 mm | A. shastensis |
4. Heads usually 5–10 (axillary clusters usually forming elongate or broad aggregates); involucres 2.5–3.5(–4) mm | → 5 |
5. Leaves alternate on distal 1/4–1/2 of stems; involucres 3–3.5(–4) mm; corollas pink, bluish, or white tinged with purple (not orange-veined); cypselae sessile-glandular | A. occidentalis |
5. Leaves alternate (from bases to apices of stems); involucres 2.5–3 mm; corollaswhite (prominently orange-veined); cypselae eglandular | A. thyrsiflora |
6. Peduncles densely stipitate-glandular | A. adenophora |
6. Peduncles puberulent, glabrous, or glabrescent (not glandular) | → 7 |
7. Flowering in spring; leaves usually narrowly lanceolate, 0.5–1.5 cm wide,apically long-acuminate; involucres 2.5–3 mm; cypselae glabrous | A. paupercula |
7. Flowering in fall; leaves ovate to lanceolate-ovate, triangular, or lanceolate, (0.5–)1.5–9 cm wide, apically acute to acuminate; involucres (in A. jucunda 2.5–)3.5–7 mm; cypselae usually hairy (glabrous in A. altissima) | → 8 |
8. Leaves mostly sessile; heads in open, loose arrays, peduncles 10–60 mm | A. lemmonii |
8. Leaves distinctly petiolate; heads in compact clusters, ultimate peduncles 1–15(–20) mm | → 9 |
9. Petioles 1–22 mm (distal leaves greatly reduced in size well proximal to heads); leaf blades 2–7(–9) × 1.5–4 cm (relatively thick) | → 10 |
9. Petioles (5–)10–70 or 2–20 (in A. rothrockii) mm; leaf blades 2–11(–13) × 1.5–9 cm (relatively thin) | → 11 |
10. Petioles 1–8(–12) mm; leaf margins crenate or less commonlycrenate-serrate to dentate or subentire | A. aromatica |
10. Petioles 7–15(–22) mm; leaf margins coarsely serrate or incised orless commonly crenate to subentire | A. jucunda |
11. Leaves (yellow-green or grayish yellow-green): blades triangular to lanceolate-ovate or ovate, 2–5(–7) × 1.5–3.5(–4.5) cm; phyllariesusually granular-puberulent | A. herbacea |
11. Leaves (green, rarely yellowish): blades lanceolate to lanceolate-ovate, 4–11(–13) × 2.5–9 cm; phyllaries glabrous, villous, or villous-puberulent | → 12 |
12. Stems glabrous; leaf blades broadly deltate-ovate (thin, delicate), apices obtuse; corolla lobes glabrous or sparselypuberulent | A. luciae-brauniae |
12. Stems puberulent; leaf blades deltate-ovate to ovate or broadly lanceolate, apices acute to acuminate; corolla lobes short-villous | → 13 |
13. Peduncles 1–5 mm; involucres 4–5 mm; cypselae glabrous;e United States and Canada | A. altissima |
13. Peduncles 5–12(–20) mm; involucres 5–7 mm; cypselae sparsely and finely strigose-hirsute; Arizona, New Mexico, sw Texas | A. rothrockii |
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