Burrobush

Hymenoclea salsola Torrey & A. Gray, Mem. Amer. Acad. Arts, n. s. 4: 79. 1849

Shrubs, 20–80(–150+) cm. Stems erect. Leaves mostly alternate; petioles 0; blades mostly filiform, 15–35(–65+) × 0.5–1.5 mm, sometimes with 3(–5+) filiform lobes, abaxial faces sparsely scabrellous, glabrescent, often vernicose, adaxial faces densely scabrellous (white). Pistillate heads ± intermixed with staminates; florets 1. Staminate heads: peduncles 0–0.5 mm; involucres ± cup-shaped, 1–3(–4) mm diam., ± glabrate, ± vernicose or gland-dotted; florets 5–15+. Burs: bodies plumply fusiform, 3–4(–6) mm, stipitate-glandular, wings 5–20+, ± scattered, broadly cuneiform, flabellate, or orbiculate, 3–4(–6) × 2–4(–8) mm. 2n = 36.

Flowering Mar–May(–Jun). Desert washes, sandy and gravelly benches, lava talus; 200–1800 m; Ariz., Calif., Nev., Utah; Mexico (Baja California, Sonora).

Variety salsola refers to plants bearing burs with 6–14 wings in 2–3+ cycles, their tips ± spreading to patent; var. pentalepis (Rydberg) Strother & B. G. Baldwin refers to plants bearing burs with 5–9(–13) wings in 1(–2) cycles, their tips ± spreading to patent; var. fasciculata (A. Nelson) Strother & B. G. Baldwin [= Hymenoclea salsola var. patula (A. Nelson) K. M. Peterson & W. W. Payne, an illegitimate name] refers to plants bearing burs with 10–18 wings in 2–3+ cycles, their tips antrorsely ± appressed (see K. M. Peterson and W. W. Payne 1973).

Hybrids between Ambrosia salsola and A. dumosa have been called A. ×platyspina (Seaman) Strother & B. G. Baldwin.