Ambrosia pumila

Perennials, 10–20(–40+) cm. Stems erect. Leaves mostly alternate (sometimes crowded at bases of stems); petioles 5–35(–55) mm; blades deltate to elliptic, 15–35(–75) × 12–25(–45) mm overall, laciniately (1–)2(–3)-pinnately lobed, bases cuneate to truncate, ultimate margins entire, abaxial and adaxial faces ± strigillose to sericeous (often grayish) and gland-dotted. Pistillate heads clustered, proximal to staminates; florets 1. Staminate heads: peduncles 0.5–6 mm; involucres obliquely cup-shaped, 3–5 mm diam., ± strigillose; florets 8–25+. Burs: bodies ± fusiform, 2–2.5 mm, strigillose, spines or tubercles 0 or 1–5, mostly distal, stoutly conic, 0.1–0.5 mm, tips straight. 2n = 72.

Phenology: Flowering May–Jun(–Oct).
Habitat: Disturbed sites, damp to wet, alkaline soils
Elevation: 100–200 m

Calif., Mexico (Baja California).

Discussion

Selected References

None.

Lower Taxa