Conyza
conyza, horseweed
usually erect, branched mostly distally (spreading and branched throughout in C. ramosissima), glabrous or hispid, hispidulous, strigillose, or strigose.
basal and cauline (mostly cauline at flowering); alternate;
petiolate or sessile;
blades mostly lanceolate to oblanceolate or linear, margins rarely lobed, ultimate toothed or entire, faces usually hispid, hispidulous, strigillose, or strigose (eglandular).
± turbinate, 2–5[–7+] mm diam.
± flat, pitted or smooth, epaleate.
3–30+, bisexual, fertile;
corollas yellowish (nerves sometimes prominently resinous), tubes shorter than narrowly funnelform throats, lobes 5, erect or spreading, deltate;
style-branch appendages deltate.
20–40+ in 2–4 series, appressed (usually reflexed in fruit), the larger usually 3-nerved (midnerves orange to brownish; not notably keeled), lanceolate to linear, unequal, ± herbaceous medially, margins membranous, abaxial faces glabrous or hirsutulous, hispidulous, or strigose.
radiate or disciform, usually in spreading to strict, paniculiform or corymbiform arrays (borne ± singly in C. ramosissima).
compressed, oblong to elliptic, 1-nerved on each edge, faces glabrous or strigillose (hairs 0.05–0.1+ mm), eglandular;
pappi persistent, of 15–25+ pinkish, sordid, tawny, or white, ± equal, barbellulate, apically attenuate bristles in 1 series.
(“ray”) florets pistillate, fertile: either 20–45+ in 1–2+ series, corollas white to purplish (filiform with laminae filiform to elliptic, 0.1–1[–1.5+] mm), or 20–150+ in 2–5+ series, corollas ochroleucous (filiform, laminae lacking, distally truncate or 2–5-toothed).
= 9.
Conyza
Species 25–40+ (4 in the flora).
Distinctions between Conyza and Erigeron, as usually circumscribed in the past 50+ years, are not always clear. Usually, conyzas have unequal (graduated) phyllaries and 2–20+ times as many pistillate florets as bisexual florets in each head (rarely more bisexual than pistillate), and corollas of pistillate florets either lack laminae or have laminae usually less than 1(–1.5) mm. Erigerons usually have subequal phyllaries and more bisexual than pistillate florets (rarely more pistillate than bisexual) and corollas of pistillate florets (if any) usually have laminae 2–10+ mm.
In studies by R. D. Noyes (2000) and by Noyes and L. H. Rieseberg (1999), Conyza, as traditionally circumscribed, was found to be nested within Erigeron and to be para- and/or polyphyletic. Here, absent an alternate taxonomy, four species traditionally treated in Conyza are retained in Conyza and a separate suite of six species that have usually been included in Conyza are treated in Laënnecia.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Plants spreading, 5–25 cm, branched throughout (stems usually ± strigose); receptacles 0.7–1 mm diam. in fruit | C. ramosissima |
1. Plants erect, (10–)30–350+ cm, branched mostly distally; receptacles 1–5 mm diam. in fruit | → 2 |
2. Phyllaries usually hispidulous or strigose; receptacles 3–5 mm diam. in fruit; pistillate florets 60–150+; pappi 3–4+ mm | C. bonariensis |
2. Phyllaries glabrous or sparsely strigose; receptacles 1–3 mm diam. in fruit; pistillate florets 20–45+; pappi 2–3 mm | → 3 |
3. Phyllaries usually sparsely strigose; corollas of pistillate florets with laminae 0 or to 0.3 mm; cypselae pale tan (usually some in each head with reddish nerves) | C. floribunda |
3. Phyllaries usually glabrous, sometimes sparsely strigose; corollas of pistillate florets with laminae 0.3–1+ mm; cypselae uniformly pale tan to light gray-brown | C. canadensis |
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WA
Flora NW
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
