Nodding Beggartick

Foodplant / internal feeder
larva of Dioxyna bidentis feeds within capitulum of Bidens cernua
Remarks: Other: uncertain

In Great Britain and/or Ireland:
Foodplant / parasite
Podosphaera fusca parasitises live Bidens cernua

Bidens cernua is used medicinally to treat urinary-tract infections.

Annuals, (2–)20–100(–400+) cm (stems sometimes rooting at proximal nodes). Leaves (rarely in 3s) sessile; blades lance-ovate or oblanceolate to lanceolate or linear, 40–100(–200+) × (2–)5–25(–45+) mm, bases cuneate to rounded, margins usually coarsely dentate to serrate, sometimes entire, sometimes ciliate, apices acute to acuminate, faces glabrous. Heads (erect or nodding at flowering, usually nodding in fruit) borne singly or in open, ± corymbiform arrays. Peduncles 10–40(–100+) mm. Calyculi of (3–)5–8(–10) spreading to reflexed, oblong to lance-linear, often ± foliaceous bractlets or bracts (3–)8–12(–25+) mm, margins usually ciliate, abaxial faces usually glabrous, bases sometimes hispidulous. Involucres ± hemispheric or broader, (3–)6–10 × (8–)12–20+ mm. Phyllaries 6–8+, ovate or lance-ovate to lanceolate, 2–10 mm. Ray florets usually 6–8, sometimes 0; laminae orange-yellow, 2–15(–18) mm. Disc florets (10–)40–100(–150+); corollas orange-yellow, 3–4 mm. Cypselae blackish or brown, usually ± flattened, sometimes ± 4-angled, ± cuneate, outer (3–)5–6+ mm, inner 4–8 mm, margins (± thickened or winged) retrorsely ciliate, apices ± truncate to convex, faces ± striate, glabrous or tuberculo-strigillose; pappi of (2–)4, ± erect, retrorsely barbed awns (1–)2–4 mm. 2n = 24, 48.

Widespread in N. Hemisphere.

2300-2600 m

Bidens cernua var. elliptica Wiegand; B. cernua var. integra Wiegand; B. cernua var. minima (Hudson) Pursh; B. cernua var. oligodonta Fernald & H. St. John; B. cernua var. radiata de Candolle; B. filamentosa Rydberg; B. glaucescens Greene; B. gracilenta Greene; B. minima Hudson; B. prionophylla Greene

Bidens cernua is a species of flowering plant in the aster family, Asteraceae. Bidens cernua is distributed throughout much of Eurasia and North America. It is commonly called nodding beggarticks or nodding bur-marigold.