Annuals, (5-)10-30(-60+) cm. Leaves: petioles 3-20 mm; blades usually rounded-deltate overall, 10-30+ × 5-20+ mm, 1-2-pinnatisect, ultimate lobes linear to filiform, 2-25 × 0.5-1(-2) mm, bases obscurely cuneate, ultimate margins minutely, if at all, ciliate, apices obtuse to acute (sometimes apiculate), faces glabrous or sparsely hirtellous. Heads usually borne singly. Peduncles 10-50(-100) mm. Calyculi of (1-)3(-5), appressed to spreading, linear bractlets (1-)3(-4) mm, margins minutely, if at all, ciliate, abaxial faces usually glabrous, sometimes sparsely hispidulous. Involucres ± cylindric, 3.5-5 × (1-)2-3 mm. Phyllaries 5-6, lance-elliptic to lanceolate, 2.5-4(-5) mm. Ray florets 0 or 1-3+; laminae yellowish, 1-4 mm. Disc florets 5-9(-13); corollas yellowish, 1-1.5 mm. Cypselae red-brown to blackish (sometimes with lighter blotches), outer ± obcompressed and linear, 3-5 mm, margins not ciliate, apices ± truncate, faces 2-grooved, usually glabrous; inner similar, ± equally 4-angled, linear-fusiform, (6-)7-12 mm, apices ± attenuate; pappi 0, or of 2(-3) spreading to divergent, retrorsely barbed awns 1-2 mm. Flowering Sep-Oct. Seeps on rocky slopes; 1500-2800 m; Ariz., Colo., N.Mex.; Mexico (Baja California, Chihuahua, Sinaloa, Sonora).
FNA 2006, Kearney and Peebles 1969
Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Small herbaceous annuals to perennials, to 30 or more cm tall. Leaves: Leaves opposite, pinnatifid 1-2 times, the ultimate lobes linear to filiform, to 1 mm wide or less, margins sometimes minutely ciliate, faces glabrous or sparsely pubescent with minute and somewhat rigid hairs. Flowers: Heads radiate, rays yellow, 1-3, to 4 mm long, disks 5-9 with yellowish corollas, outer row of bracts linear, appressed to spreading bractlets, involucres cylindric, 2-3 mm high, heads in groups of 5-9, borne singly at branch tips. Fruits: Achenes red-brown to black, elongate, usually twice as long as the inner phyllaries, glabrous, 3-5 mm long, linear, dorsally compressed, margins not ciliate, faces with 2 grooves, the pappus of 2-3 spreading to divergent, retrorsely barbed awns. Ecology: Found near seeps, on rocky slopes, from 5,500-9,000 ft (1676-2743 m); flowering September-October. Distribution: Southern Colorado to New Mexico, Arizona; Mexico. Notes: The genus Bidens is easy to identify by its yellow flowers and achenes which readily attach to clothing, fur, and everything else. Good indicators for this species are the linear, glabrous achenes, the 1-2 times pinnately dissected leaves and narrow, linear leaf divisions, the cylindric heads, and the groups of 5-9 flower heads. Ethnobotany: Unknown for this species, others in genus have many uses. Etymology: Bidens is derived from the Latin bis, twice and dens, tooth, hence meaning 2-toothed, while heterosperma means different seed. Synonyms: None Editor: LCrumbacher 2011