Bidens aristosa
Bidens pilosa
bearded beggarticks, long-bract beggar-ticks, midwestern beggar-ticks, tickseed sunflower
bident poilu, cobbler's pegs, common beggar-ticks, hairy beggar-ticks, Spanish needle
petioles 10–30 mm;
blades lanceolate to lance-linear overall, 30–80(–150) × 10–30(–50) mm, usually laciniately pinnatisect, primary lobes 3–7+, 15–60+ × 2–20 mm, bases cuneate, ultimate margins laciniate to serrate, ciliate, apices acuminate, faces glabrous or sparsely scabrellous.
petioles 10–30(–70) mm;
blades either ovate to lanceolate, 30–70(–120) × 12–18(–45) mm, or 1-pinnately lobed, primary lobes 3–7, ovate to lanceolate [linear], (10–)25–80+ × (5–)10–40+ mm [blades 2(–3)-pinnatisect], bases truncate to cuneate, ultimate margins serrate or entire, usually ciliate, apices acute to attenuate, faces pilosulous to sparsely hirtellous or glabrate.
(10–)30–80+ mm.
10–20(–90) mm.
± hemispheric or broader, 6–8(–12) × 10–15 mm.
turbinate to campanulate, 5–6 × (6–)7–8 mm.
(5–)8–10+;
laminae yellow, 10–25 mm.
0 or (3–)5–8+;
laminae whitish to pinkish [yellowish], 2–3 or 7–15+ mm.
(12–)20–40+;
corollas yellowish, 2–3+ mm.
20–40(–80+);
corollas yellowish, (2–)3–5 mm.
7–8(–13), lance-ovate to lance-linear, 6–8(–12) mm.
(7–)8–9(–13), lanceolate to oblanceolate, 4–6 mm.
of 8–12(–16) usually spreading to reflexed, linear, seldom foliaceous bractlets (4–)5–7(–12) mm, margins entire, ciliate, abaxial faces glabrous or ± scabrellous.
(6–)7–9(–13) ± appressed, spatulate to linear bractlets (3–)4–5 mm, margins ciliate, abaxial faces usually hispidulous to puberulent.
in ± corymbiform arrays.
usually borne singly, sometimes in open, ± corymbiform arrays.
red-brown to blackish, ± flattened (unequally 3–4-angled), broadly cuneate, outer (4–)5–6 mm, inner 5–7 mm (lengths mostly 1.5–2.5 times widths), margins (± corky-winged) patently to antrorsely barbed, apices truncate to concave, faces weakly striate, sometimes tuberculate, glabrous or sparsely strigillose;
pappi 0, or of 2(–4) spreading to divergent, antrorsely or retrorsely barbed awns (0.5–)2–4(–6) mm.
outer red-brown, ± flat, linear to narrowly cuneate, (3–)4–5+ mm, margins antrorsely hispidulous, apices ± truncate or somewhat attenuate, faces obscurely 2-grooved, sometimes tuberculate-hispidulous;
inner blackish, ± equally 4-angled, linear-fusiform, 7–16 mm, margins antrorsely hispidulous, apices ± attenuate, faces 2-grooved, tuberculate-hispidulous to sparsely strigillose;
pappi 0, or of 2–3(–5), erect to divergent, retrorsely barbed awns (0.5–)2–4 mm.
= 24, 36, 48, 72.
Bidens aristosa
Bidens pilosa
R. Ballard (1986) adopted a narrower circumscription of Bidens pilosa than that used here. He used: B. pilosa for plants with outer phyllaries 7–10, ray florets usually 0 (when present, laminae 2–3 mm), disc florets 35–75, pappi of 3(–5) awns 1–3 mm, and 2n = 72; B. alba for plants with outer phyllaries (8–)12(–16), ray florets 5–8 (laminae 5–16 mm), pappi of 2 awns 1–2 mm, and 2n = 48; and B. odorata for plants with outer phyllaries (6–)8(–12), ray florets 5–8 (laminae 3–18 mm), disc florets 12–61, pappi 0, or of 1–2 awns 1–3 mm, and 2n = 24.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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