Ageratina
Ageratina altissima
snakeroot
white snakeroot
usually erect, rarely scandent, sparsely to densely branched.
ascending to erect, sometimes semiscandent, puberulent (hairs minute, crisped).
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).
opposite;
petioles (5–)10–30(–50) mm;
blades usually deltate-ovate to ovate or broadly lanceolate, sometimes ovate-lanceolate, 4–11(–13) × 2.5–8(–9) cm, bases usually rounded to truncate or obtuse, sometimes cordate, margins coarsely and doubly incised-serrate, apices usually acuminate.
1–5 mm, puberulent.
campanulate, 3–6 mm diam.
4–5 mm.
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 sparsely short-villous.
persistent, 8–30 in 2(–3) series, 0- or 2-nerved, lanceolate to linear, ± equal (herbaceous).
apices acute, abaxial faces glabrous or sparsely and finely villous.
discoid, usually in compact, (terminal and axillary) corymbiform arrays, sometimes borne singly.
clustered.
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.
glabrous.
= 17.
Ageratina
Ageratina altissima
Species ca. 250 (14 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Varieties 2 (2 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 |
1. Phyllaries 3–5 mm, apices not cuspidate | var. altissima |
1. Phyllaries 4–7 mm, apices cuspidate to acuminate | var. roanensis |
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