Shrubs, 30-150(-400) cm. Stems erect. Leaves mostly alternate; petioles 0; blades mostly filiform, 5-30(-65+) × 0.5-1.5 mm, sometimes with 3(-5+) filiform lobes, abaxial faces glabrous or glabrate, often vernicose, adaxial faces densely scabrellous (white). Pistillate heads ± intermixed with staminates; florets 1. Staminate heads: peduncles 0-0.5 mm; involucres ± cup-shaped, 2-4 mm diam., ± glabrate, ± vernicose; florets 5-12+. Burs: bodies fusiform to pyriform, 4-5 mm, stipitate-glandular, wings 7-12+, mostly around middles, oblanceolate to cuneiform, 2-3 × 1-2 mm. 2n = 36. Flowering (May-)Aug-Nov. Desert washes, ravines; 10-500 m; Ariz., Calif., N.Mex., Tex.; Mexico (Baja California, Baja California Sur, Chihuahua, Sinaloa, Sonora). Ambrosia monogyra may occur in western Nevada.