Ageratum conyzoides
Asteraceae tribe eupatorieae
tropical whiteweed
erect, sparsely to densely villous.
blades ovate to elliptic-oblong, 2–8 × 1–5 cm, margins toothed, abaxial faces sparsely pilose and gland-dotted.
usually cauline, sometimes basal or basal and cauline; usually opposite, sometimes whorled or alternate; usually petiolate, sometimes sessile;
blade margins entire, toothed, lobed, or dissected.
minutely puberulent and sparsely to densely pilose, eglandular.
3–3.5 × 4–5 mm.
usually flat to convex, sometimes spheric or conic, usually epaleate, rarely paleate (paleae readily falling).
0.
bisexual, fertile;
corollas white, ochroleucous, or pink to purplish, not yellow, not 2-lipped (sometimes ± zygomorphic), lobes (4–)5, usually ± deltate to lance-ovate, sometimes lanceolate to lance-linear;
anther bases obtuse, rounded, or truncate, not tailed, apical appendages usually ovate to lanceolate, sometimes 0;
styles abaxially papillate to hirsutulous (usually distally, sometimes at bases), branches ± linear, adaxially stigmatic in 2 lines from bases to appendages, appendages usually terete to clavate (lengths often 2–5+ times lengths of stigmatic lines), usually papillate.
usually blue to lavender, sometimes white.
oblong-lanceolate (0.8–1.2 mm wide), glabrous or sparsely pilose (margins often ciliate), eglandular, tips abruptly tapering, subulate, 0.5–1 mm.
usually persistent (readily falling), usually in 2–8+ series, distinct, and unequal, sometimes in 1–2 series, distinct, and subequal to equal, usually herbaceous to chartaceous, margins and/or apices sometimes scarious (abaxial faces often striate-nerved).
0.
homogamous (usually discoid [radiant]), usually in corymbiform, paniculiform, racemiform, or spiciform arrays, sometimes borne singly or in glomerules.
sparsely strigoso-hispidulous;
pappi usually of scales 0.5–1.5(–3) mm, sometimes with tapering setae, rarely 0.
usually ± monomorphic within heads, usually columnar to fusiform, sometimes prismatic or compressed to flattened, rarely, if ever, beaked, bodies often 10-ribbed or (4–)5-angled, smooth or papillate to rugose between ribs or angles (glabrous or hairy);
pappi (rarely 0) usually persistent, usually of fine to coarse, barbellulate to plumose bristles, sometimes of scales (scales often aristate) or awns, sometimes of bristles and scales.
= 20, 40.
Ageratum conyzoides
Asteraceae tribe eupatorieae
Ageratum conyzoides is apparently native to South America. North American plants were escapes and naturalized from cultivation.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Genera 170, species 2400 (27 genera, 159 species in the flora).
In a survey of Compositae, G. Bentham (1873) noted 35 genera and 750 or so species for Eupatorieae; he treated more than 50% of those species as belonging within one genus, Eupatorium. The current view of circumscriptions of most genera within Eupatorieae has stemmed largely from the work of H. Robinson, which was summarized by R. M. King and Robinson (1987), who reported 45 species for Eupatorium (i.e., ca. 2 % of the total species in the tribe).
Authors of molecular studies have repeatedly found Eupatorieae to be a coherent clade “nested” within Heliantheae (broad sense) (e.g., R. K. Jansen et al. 1990). Some of those authors have suggested inclusion of Eupatorieae within Heliantheae in the broad sense as a subtribe; others have suggested break-up of Heliantheae into a dozen or so tribes (e.g., J. L. Panero and V. A. Funk 2002).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Involucres narrowly cylindric, (1–)2–3 mm diam.; phyllaries 4 or 5(–6) in ± 1–2 series; florets 4 or 5(–6) | → 2 |
1. Involucres campanulate, cylindric, ellipsoid, hemispheric, or obconic, (2–)3–7(–25) mm diam.; phyllaries (5–)8–45(–65+) in (1–)2–8+ series; florets (3–)10–125(–200+). | → 3 |
2. Subshrubs or shrubs; phyllaries 5(–6); florets 5(–6) | Stevia |
2. Vines; phyllaries 4; florets 4 | Mikania |
3. Cypselae 8–10-ribbed | → 4 |
3. Cypselae (3–)4–5(–8)-ribbed | → 9 |
4. Pappi of 0–5+, muticous, erose, lacerate, or lanceolate to subulate scales (1–4 mm) plus [5–]9–12+, aristate scales (10–15 mm) | Carphochaete |
4. Pappi of 10–100+ bristles | → 5 |
5. Leaves basal or basal and cauline (cauline mostly sessile) | → 6 |
5. Leaves mostly cauline (at flowering; mostly petiolate, sometimes sessile) | → 7 |
6. Heads usually in spiciform or racemiform, rarely corymbiform or thyrsiform, arrays; receptacles epaleate; pappi of 12–40 coarsely barbellate to plumose bristles | Liatris |
6. Heads in corymbiform to paniculiform arrays; receptacles sometimes (at least partially) paleate; pappi of 35–40 barbellulate to barbellate (subequal) bristles | Carphephorus |
7. Leaves all or mostly alternate (at flowering) | Garberia |
7. Leaves all or mostly opposite | → 8 |
8. Leaf blades deltate, lance-elliptic, lance-linear, lanceolate, lance-ovate, lance-rhombic, linear, oblong, obovate, ovate, rhombic-ovate, spatulate, or suborbiculate, margins crenate, dentate, entire, laciniate-dentate, lobed, or serrate; style bases enlarged, hairy | Brickellia |
8. Leaf blades linear (distal sometimes scalelike), margins entire; style bases not enlarged, glabrous | Asanthus |
9. Pappi usually 0 or of 2–6(–12), muticous or aristate to subulate scales plus 0–6(–12), setiform scales or bristles, rarely coroniform (Ageratum) or of 1–5 ± glandular setae (Hartwrightia) | → 10 |
9. Pappi of (5–)10–80+ barbellulate, barbellate, or plumose bristles or setiform scales | → 18 |
10. Pappi usually 0, rarely 1–5 ± glandular setae (Hartwrightia) | → 11 |
10. Pappi usually of 2–6(–12) muticous or aristate to subulate scales plus 0–6(–12),setiform scales or bristles, rarely coroniform (Ageratum) | → 14 |
11. Leaves basal and cauline, mostly alternate; cypselae obpyramidal (gland-dotted) | Hartwrightia |
11. Leaves cauline, all or mostly opposite; cypselae prismatic (not gland-dotted) | → 12 |
12. Heads in dense to open, cymiform or corymbiform arrays; phyllaries 30–40; style branches ± linear to clavate (distally dilated) | Ageratum |
12. Heads in tight, corymbiform to subcapitate arrays or borne singly; phyllaries 10–30; style branches ± filiform or linear-filiform (little, if at all, distally dilated) | → 13 |
13. Leaves sessile; phyllaries not notably nerved; receptacles epaleate; stylebases not enlarged | Shinnersia |
13. Leaves petiolate or sessile; phyllaries 2- or 3-nerved; receptacles paleate(paleae similar to inner phyllaries); style bases enlarged | Isocarpha |
14. Phyllaries unequal; receptacles flat to convex (not warty) | → 15 |
14. Phyllaries ± equal; receptacles convex to conic or hemispheric (sometimes warty) | → 16 |
15. Leaves mostly sessile (or nearly so), blades linear; cypselae ± fusiform | Malperia |
15. Leaves petiolate, blades ovate, deltate, or rhombic to lanceolate; cypselae prismatic | Pleurocoronis |
16. Leaves whorled (4 or 6 per node), blades linear; heads borne singly | Sclerolepis |
16. Leaves mostly opposite (distal sometimes alternate), blades elliptic, lanceolate, or oblong; heads usually in cymiform to corymbiform arrays, sometimes borne singly | → 17 |
17. Leaves petiolate; involucres 3–6 mm diam.; phyllaries usually 2-nerved; pappi usually of 5–6 aristate scales, rarely coroniform | Ageratum |
17. Leaves sessile; involucres 3–4(–5) mm diam.; phyllaries obscurely 3–4-nerved; pappi of 2–6 setiform scales | Trichocoronis |
18. Involucres cylindric (3–4+ mm diam); pappus bristles plumose (basally coherent or connate, falling together or in groups) | Carminatia |
18. Involucres usually obconic to hemispheric, sometimes campanulate, cylindric, or ellipsoid (2–7 mm diam.); pappus bristles smooth to barbellulate or barbellate (not plumose) | → 19 |
19. Phyllaries ± equal | → 20 |
19. Phyllaries unequal (outer shorter) | → 23 |
20. Receptacles conic | Conoclinium |
20. Receptacles flat or convex | → 21 |
21. Phyllaries 2- or 3-nerved, or not notably nerved, or pinnately nerved; style bases usually puberulent (glabrous in Eupatorium capillifolium); cypselae usually gland-dotted | Eupatorium |
21. Phyllaries 3-nerved, or 0- or 2-nerved; style bases glabrous; cypselae sometimes gland-dotted | → 22 |
22. Involucres 2–3 mm diam.; phyllaries 7–16 in 1–2 series; florets 3–13 | Koanophyllon |
22. Involucres 3–6 mm diam.; phyllaries ca. 30 in 2–3 series; florets 10–60 | Ageratina |
23. Style bases usually puberulent (glabrous in Eupatorium capillifolium); cypselae usually glabrous and gland-dotted, sometimes scabrellous on ribs | → 24 |
23. Style bases usually glabrous (hirsute in Flyriella); cypselae glabrous or hirsute, hirtellous, hispidulous, hispidulo-strigose, puberulent, or scabrellous (sometimes gland-dotted) | → 25 |
24. Leaves mostly opposite (sometimes whorled, distal sometimes alternate) | Eupatorium |
24. Leaves mostly whorled (3–7 per node), rarely opposite | Eutrochium |
25. Annuals or perennials; involucres 2–5+ mm diam.; florets 10–30 | → 26 |
25. Perennials, subshrubs, or shrubs; involucres (2–)4–7 mm diam.; florets (3–)25–50 | → 27 |
26. Perennials, 20–60 cm (viscid); corollas white to ochroleucous, throats ± cylindric (± contracted distally, lengths 4–6 times diams.) | Flyriella |
26. Annuals or perennials, 30–120+ cm (not viscid, stems usually puberulent, hairs curled); corollas bluish, pinkish, purplish, or white, throats funnelform (not contracted distally, lengths 2.5–4 times diams.) | Fleischmannia |
27. Phyllaries usually readily falling, 18–65+ in 4–6+ series, 3–5-nerved; cypselae (3–)5-ribbed, scabrellous, usually gland-dotted | Chromolaena |
27. Phyllaries usually persistent, 7–35 in (1–)2–4 series, 2- or 4-nerved, 3-nerved, or obscurely nerved; cypselae 5(–7)-ribbed, hispidulous, hispidulo-strigose, puberulent, or sparsely scabrellous (sometimes gland-dotted) | → 28 |
28. Phyllaries 2- or 4-nerved; corollas white to yellowish white; pappi readily falling or fragile | Brickelliastrum |
28. Phyllaries 3-nerved or obscurely nerved; corollas usually blue, lavender, or pinkish, sometimes white; pappi persistent | → 29 |
29. Involucres 5–7 mm diam.; phyllaries 30–35; florets 30–50 | Tamaulipa |
29. Involucres 2–3 mm diam.; phyllaries 7–16; florets 3–13 | Koanophyllon |
CalFlora
Go Botany
MD Biodiversity
MO Plants
WildflowerSearch
iNaturalist
USDA Plants Database
