Shrubs, 30-80+ cm. Stems erect. Leaves mostly alternate; petioles 5-12+ mm; blades deltate to lance-deltate, 12-25(-35) × 5-12(-18) mm, bases cuneate to truncate, margins toothed, abaxial faces ± densely tomentulose (between veins), adaxial faces sparsely tomentulose, glabrescent. Pistillate heads clustered, proximal to staminates; florets 2-3. Staminate heads: peduncles 0.5-3(-5) mm; involucres ± cup-shaped, 4-8 mm diam., tomentulose; florets 12-30+. Burs: bodies ± fusiform to globose, 3-4 mm, usually stipitate-glandular (little, if at all, tomentulose), spines 20-30+, scattered or on distal ¹/2, ± subulate (the proximal basally flattened), 1-3 mm, tips usually straight, sometimes uncinate. 2n = 36. Flowering Feb-May. Sandy washes, benches; 200-1000 m; Ariz.; Mexico (Baja California, Sonora). Some specimens are intermediate for the char­-acteristics that distinguish Ambrosia deltoidea and A. chenopodiifolia. The type of A. deltoidea may be better treated as conspecific with that of A. chenopodiifolia.

Notes: receptacle envelopes pistils in spiny covering References: L. Benson & R. Darrow. Trees and Shrubs of the Southwestern Deserts. Kearney & Peebles. Arizona Flora. ASU specimens.