Ambrosia acanthicarpa

Annuals, 10–80+ cm. Stems erect. Leaves opposite (proximal) and alternate; petioles 5–15(–25+) mm; blades ± deltate, 15–40(–85+) × 12–35(–80+) mm, 1–2-pinnately lobed, bases cuneate, ultimate margins entire or toothed, abaxial faces hispid and strigillose to sericeous, adaxial faces strigillose and gland-dotted. Pistillate heads clustered, proximal to staminates; florets 1. Staminate heads: peduncles 0.5–2 mm; involucres shallowly cup-shaped (usually each with 1–5+ black nerves), 3–5(–7) mm diam., sparsely hirsute or glabrous; florets 6–12(–20+). Burs: bodies fusiform to obpyramidal, 3–5 mm, ± hirsutulous or glabrate, spines 8–18+, scattered, stoutly subulate (sometimes basally flattened or navicular), 2–4(–5) mm, tips straight or uncinate. 2n = 36.

Phenology: Flowering (Apr–)Jul–Nov.
Habitat: Canyons, sandy flats, dunes
Elevation: 10–3000 m

Alta., Man., Sask., Ariz., Calif., Colo., Idaho, Kans., Minn., Mo., Mont., Nebr., Nev., N.Mex., N.Dak., Okla., Oreg., S.Dak., Tex., Utah, Wash., Wyo.

Discussion

Selected References

None.

Lower Taxa