Annuals, (10–) 20–40 cm. Leaves: petioles 5–40 mm; blades rounded-deltate to ovate overall, 20–50+ × 15–35+ mm, (1–) 2–3-pinnatisect, ultimate lobes ± linear, (2–) 5–15+ × (0.5–) 2–3+ mm, bases ± cuneate, ultimate margins entire, sometimes ciliolate, apices acute to attenuate, faces usually glabrous, sometimes hispidulous. Heads usually borne singly, sometimes in 2s or 3s. Peduncles 20–30 (–80) mm. Calyculi of 6–12 ± appressed, linear bractlets 5–7 mm, margins scabro-ciliate, abaxial faces usually pilosulous to hirsutulous, rarely glabrous. Involucres campanulate to hemispheric or broader, (5–) 6–7 × 4–8 mm. Phyllaries 8, lance-linear, 5–7 mm. Ray-florets 0 or 3–6; laminae yellow, 4–6 mm. Disc-florets (5–) 12–20 (–45); corollas yellow, 2–3 mm. Cypselae: outer redbrown, flat or weakly 4-angled, linear, 6–8 mm, margins not ciliate, apices somewhat attenuate, faces obscurely 2-grooved, often tuberculate, glabrous or ± strigillose; inner similar, blackish (sometimes with pale tips), ± equally 4-angled, linear-fusiform, 8–15 mm, margins not ciliate, apices attenuate, faces 2-grooved, glabrous or, toward tips, strigillose; pappi of 2 (–3), spreading to divergent, retrorsely barbed awns (1–) 1.5–3 mm.

Phenology: Flowering (Jul–)Aug–Sep(–Oct).
Habitat: Meadows, along streams
Elevation: 1800–2600 m

Distribution

• Generated Map
• Legacy Map

Ariz., Colo., Idaho, N.Mex., Utah, Mexico (Chihuahua)

Discussion

Reports of Bidens tenuisecta from Maryland, Massachusetts, and New York may be based on ephemeral introductions.

Selected References

None.

Lower Taxa

None.