Ambrosia tomentosa
Gen. N. Amer. Pl. 2: 186. 1818.
Perennials, 10–30+ cm. Stems erect. Leaves mostly alternate; petioles 8–25(–35+) mm; blades elliptic to lance-elliptic, 50–80(–180+) × 12–20(–50+) mm overall, (1–)2(–3)-pinnately lobed (lobes ± deltate), bases cuneate, ultimate margins with ± deltate teeth, abaxial faces densely finely scabrellous (silvery gray), adaxial faces strigillose. Pistillate heads clustered, proximal to staminates; florets (1–)2. Staminate heads: peduncles 2–9 mm; involucres saucer-shaped (with black nerves), 3–6+ mm diam., strigillose; florets 25–40+. Burs: bodies ± pyriform, somewhat flattened, 1.5–2.5(–4) mm, finely scabrellous, spines (1–)8–12+, scattered, stoutly conic, 0.5–1+ mm, tips straight.
Phenology: Flowering Jun–Sep.
Habitat: Seasonally wet clays or sands, disturbed sites
Elevation: (200–)1200–2100 m
Distribution
Ariz., Colo., Idaho, Ill., Iowa, Kans., Mo., Mont., Nebr., N.Mex., N.Dak., S.Dak., Tex., Utah, Wis., Wyo.
Discussion
Selected References
None.