Annuals, (10-)15-25(-30+) cm. Leaves: petioles 10-20 mm; blades either oblanceolate to linear, 5-15+ × 1-2+ mm, or rounded-deltate overall, 10-25(-60+) × 15-25+ mm, (1-)2-3-pinnatisect, ultimate lobes oblanceolate to spatulate or linear, 5-15+ × 0.5-5 mm, bases ± cuneate, ultimate margins entire, sometimes ciliolate, apices obtuse to acute, faces glabrous. Heads usually borne singly, sometimes in open, ± corymbiform arrays. Peduncles 10-20(-90) mm. Calyculi of (1-)3-4 appressed to spreading, spatulate to linear bractlets or bracts 3-10(-25+) mm (sometimes foliaceous: pinnate, lobes 3-5+, linear), margins ciliolate, abaxial faces usually glabrous, sometimes sparsely hispidulous. Involucres ± campanulate to cylindric, 2-3(-8) × 2(-3)[-4] mm. Phyllaries (3-)5, oblong to lanceolate orlinear, (2-)3-8 mm. Ray florets 0 or 1(-3+); laminae whitish, 1-1.5(-3+) mm. Disc florets (3-)5-9; corollas whitish to yellowish, 2-2.5 mm. Cypselae: outer red-brown (sometimes with lighter blotches), ± equally 4-angled, linear-fusiform, 5-6(-8) mm, margins not ciliate, apices ± attenuate, faces 2-grooved, usually glabrous; inner similar, 10-14 mm; pappi of 2-3 erect, retrorsely barbed awns 1-2(-3) mm.

Flowering Sep-Oct. Wettish spots on rocky slopes; 1400-2100 m; Ariz., N.Mex.; Mexico.

Duration: Perennial

Nativity: Native

Lifeform: Forb/Herb

General: Annual herbs, 15-25 cm high or occasionally taller.

Leaves: Opposite, on petioles 1-2 cm long; blades 2-3 times pinnately lobed, the ultimate lobes linear, 1-5 mm wide, glabrous, the margins sometimes ciliate.

Flowers: Flower heads yellow, radiate or discoid, subsessile or on short 1-2(-9) cm peduncles, usually solitary but sometimes arranged in open, flat-topped panicles; calyculi (extra set of bracts just below the involucre) of 3-4 appressed to spreading, linear or pinnately lobed bractlets, 3-25 mm long; involucre (ring of bracts wrapped around the flower head) campanulate to cylindric, to 3 mm or more high and shorter than the calyculi, the bracts (phyllaries) 5, lanceolate; ray flowers absent or up to 3, the corolla laminae (ray petals) whitish, 2 mm long; disc flowers 5-9, the corollas yellow to whitish, 2 mm high.

Fruits: Achenes red-brown, linear, 4-angled, faces 2-grooved, margins not ciliate, with a pappus of 2-3 erect, retrorsely barbed awns, 1-2 mm long.

Ecology: Found in moist microclimates on rocky slopes, from 4,500-7,000 ft (1372-2134 m); flowers September-October.

Distribution: s AZ, s NM; south to MEX.

Notes: Bidens is a genus of herbaceous plants with opposite leaves, discoid or radiate flower heads with yellow-orange flowers, and seeds (achenes) with 2-4 barbed awns. Good indicators for B. lemmonii are the subsessile or short-peduncled heads (B. leptocephala has longer peduncles, 3-8 cm long); the ray flowers which are often missing but when present are white (most Bidens spp. have yellow rays); the leaves with linear or linear-oblong leaf lobes 1-3 mm wide (B. bigelovii has wider leaf lobes); and the calyculi (outer bractlets of flower head) longer than the involucre (the calyculi bractlets are only 1-3 mm long and shorter than the involucre in B. leptocephala).

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 lemmonii is named for Sara Plummer Lemmon (1836-1923) and her husband John Gil Lemmon (1832-1908), who collected plants for Asa Gray all across the west.

Synonyms: None

Editor: LCrumbacher 2011, AHazelton 2015