View source for Ageratina

{{Treatment/ID
|accepted_name=Ageratina
|accepted_authority=Spach
|publications={{Treatment/Publication
|title=Hist. Nat. Vég.
|place=10: 286. 1841
|year=1841
}}
|common_names=Snakeroot
|basionyms=
|synonyms=
|hierarchy=Asteraceae;Asteraceae tribe Eupatorieae;Ageratina
|hierarchy_nav=<div class="higher-taxa"><div class="higher-taxon"><small>family</small>[[Asteraceae]]</div><div class="higher-taxon"><small>tribe</small>[[Asteraceae tribe Eupatorieae]]</div><div class="higher-taxon"><small>genus</small>[[Ageratina]]</div></div>
|etymology=Generic name Ageratum and Latin - ina, diminutive
|volume=Volume 21
|mention_page=page 461, 462, 541, 552
|treatment_page=page 547
}}<!--

--><span class="statement" id="st-undefined" data-properties=""><b>Perennials,</b> subshrubs, or shrubs [trees], mostly 20–220 cm. <b>Stems</b> usually erect, rarely scandent, sparsely to densely branched. <b>Leaves</b> 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 (<i>A. occidentalis</i>, <i>A. adenophora</i>). <b>Heads</b> discoid, usually in compact, (terminal and axillary) corymbiform arrays, sometimes borne singly. <b>Involucres</b> campanulate, 3–6 mm diam. <b>Phyllaries</b> persistent, 8–30 in 2(–3) series, 0- or 2-nerved, lanceolate to linear, ± equal (herbaceous). <b>Florets</b> 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. <b>Receptacles</b> convex (glabrous or hairy), epaleate. <b>Cypselae</b> 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. <b>x</b> = 17.</span><!--

-->{{Treatment/Body
|distribution=North America;Mexico;Central America;Andean South America.
|discussion=<p>Species ca. 250 (14 in the flora).</p>
|tables=
|references={{Treatment/Reference
|id=clewell1971a
|text=Clewell, A. F. and J. W. Wooten. 1971. A revision of Ageratina (Compositae: Eupatorieae) from eastern North America. Brittonia 23: 123–143
}}
}}<!--

--><div class="treatment-key">
==Key==
<div class="treatment-key-group">
  
{| class="wikitable fna-keytable"
|-id=key-0-1
|1
|Shrubs
|[[#key-0-2| > 2]]
|-id=key-0-1
|1
|Perennials or subshrubs
|[[#key-0-3| > 3]]
|-id=key-0-2
|2
|Petioles (2–)3–5 mm; leaf blades 1–2 cm, margins entire or shallowly crenate, facesgland-dotted
|[[Ageratina wrightii|Ageratina wrightii]]
|-id=key-0-2
|2
|Petioles 3–10(–15) mm; leaf blades (2–)3–5(–7) cm, margins coarsely crenate, facesnot gland-dotted
|[[Ageratina havanensis|Ageratina havanensis]]
|-id=key-0-3
|3
|Leaves alternate on at least distal 1/4–1/2 of stems
|[[#key-0-4| > 4]]
|-id=key-0-3
|3
|Leaves opposite
|[[#key-0-6| > 6]]
|-id=key-0-4
|4
|Heads usually borne singly (rarely 2s or 3s); involucres 11–12 mm
|[[Ageratina shastensis|Ageratina shastensis]]
|-id=key-0-4
|4
|Heads usually 5–10 (axillary clusters usually forming elongate or broad aggregates); involucres 2.5–3.5(–4) mm
|[[#key-0-5| > 5]]
|-id=key-0-5
|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
|[[Ageratina occidentalis|Ageratina occidentalis]]
|-id=key-0-5
|5
|Leaves alternate (from bases to apices of stems); involucres 2.5–3 mm; corollaswhite (prominently orange-veined); cypselae eglandular
|[[Ageratina thyrsiflora|Ageratina thyrsiflora]]
|-id=key-0-6
|6
|Peduncles densely stipitate-glandular
|[[Ageratina adenophora|Ageratina adenophora]]
|-id=key-0-6
|6
|Peduncles puberulent, glabrous, or glabrescent (not glandular)
|[[#key-0-7| > 7]]
|-id=key-0-7
|7
|Flowering in spring; leaves usually narrowly lanceolate, 0.5–1.5 cm wide,apically long-acuminate; involucres 2.5–3 mm; cypselae glabrous
|[[Ageratina paupercula|Ageratina paupercula]]
|-id=key-0-7
|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)
|[[#key-0-8| > 8]]
|-id=key-0-8
|8
|Leaves mostly sessile; heads in open, loose arrays, peduncles 10–60 mm
|[[Ageratina lemmonii|Ageratina lemmonii]]
|-id=key-0-8
|8
|Leaves distinctly petiolate; heads in compact clusters, ultimate peduncles 1–15(–20) mm
|[[#key-0-9| > 9]]
|-id=key-0-9
|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)
|[[#key-0-10| > 10]]
|-id=key-0-9
|9
|Petioles (5–)10–70 or 2–20 (in A. rothrockii) mm; leaf blades 2–11(–13) × 1.5–9 cm (relatively thin)
|[[#key-0-11| > 11]]
|-id=key-0-10
|10
|Petioles 1–8(–12) mm; leaf margins crenate or less commonlycrenate-serrate to dentate or subentire
|[[Ageratina aromatica|Ageratina aromatica]]
|-id=key-0-10
|10
|Petioles 7–15(–22) mm; leaf margins coarsely serrate or incised orless commonly crenate to subentire
|[[Ageratina jucunda|Ageratina jucunda]]
|-id=key-0-11
|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
|[[Ageratina herbacea|Ageratina herbacea]]
|-id=key-0-11
|11
|Leaves (green, rarely yellowish): blades lanceolate to lanceolate-ovate, 4–11(–13) × 2.5–9 cm; phyllaries glabrous, villous, or villous-puberulent
|[[#key-0-12| > 12]]
|-id=key-0-12
|12
|Stems glabrous; leaf blades broadly deltate-ovate (thin, delicate), apices obtuse; corolla lobes glabrous or sparselypuberulent
|[[Ageratina luciae-brauniae|Ageratina luciae-brauniae]]
|-id=key-0-12
|12
|Stems puberulent; leaf blades deltate-ovate to ovate or broadly lanceolate, apices acute to acuminate; corolla lobes short-villous
|[[#key-0-13| > 13]]
|-id=key-0-13
|13
|Peduncles 1–5 mm; involucres 4–5 mm; cypselae glabrous;e United States and Canada
|[[Ageratina altissima|Ageratina altissima]]
|-id=key-0-13
|13
|Peduncles 5–12(–20) mm; involucres 5–7 mm; cypselae sparsely and finely strigose-hirsute; Arizona, New Mexico, sw Texas
|[[Ageratina rothrockii|Ageratina rothrockii]]
|}
</div></div><!--

-->{{#Taxon:
name=Ageratina
|author=Guy L. Nesom
|authority=Spach
|rank=genus
|parent rank=tribe
|synonyms=
|basionyms=
|family=Asteraceae
|distribution=North America;Mexico;Central America;Andean South America.
|reference=clewell1971a
|publication title=Hist. Nat. Vég.
|publication year=1841
|special status=
|source xml=https://jpend@bitbucket.org/aafc-mbb/fna-data-curation.git/src/f50eec43f223ca0e34566be0b046453a0960e173/coarse_grained_fna_xml/V19-20-21/V21_1389.xml
|tribe=Asteraceae tribe Eupatorieae
|genus=Ageratina
}}<!--

-->[[Category:Treatment]][[Category:Asteraceae tribe Eupatorieae]]