Bidens hyperborea Greene

Annuals, (5–)10–30(–70+) cm. Leaves sessile or petioles 5–25 mm (± winged); blades oblanceolate to linear, 15–40(–100+) × (3–)6–10(–15+) mm, bases cuneate, margins entire or ± serrate, sometimes ciliate, apices rounded or obtuse to attenuate, faces glabrous. Heads borne singly or in 2s or 3s. Peduncles 10–60 mm. Calyculi of 2–3(–9) erect, oblanceolate to lance-linear (± foliaceous) bractlets or bracts (6–)10–20(–75+) mm, margins usually ciliolate, abaxial faces glabrous. Involucres usually ± campanulate to cylindric, sometimes ± hemispheric, 5–7(–9) × (4–)7–10 mm. Phyllaries 6–8(–12), oblong, 6–11 mm (tips usually yellow, as are tips of paleae). Ray florets 0 or 3–7; laminae pale yellow, 4–12 mm. Disc florets 15–30(–60); corollas yellow (often orange-tipped), 3–4 mm. Cypselae blackish to olive, flattened, narrowly cuneate, outer 4–9 mm, inner 5–10 mm, margins retrorsely barbed, apices ± truncate to convex, faces ± 1-nerved, ± striate, glabrous; pappi of (2–)3–4 ± erect, retrorsely barbed awns 2–5 mm.

Bidens hyperborea var. arcuans Fernald; B. hyperborea var. cathancensis Fernald; B. hyperborea var. colpophila (Fernald & H. St. John) Fernald; B. hyperborea var. gaspensis Fernald; B. hyperborea var. svensonii Fassett