Hairy milkvine

Sarcostemma heterophyllum Engelmann ex Torrey var. hirtellum A. Gray in W. H. Brewer et al., Bot. California 1: 478. 1876; S. hirtellum (A. Gray) R. W. Holm

Stems hirtellous. Leaves persis­tent or caducous, stipular colleter 1 on each side of peti­ole; petiole 0–1.5 cm, hirtellous throughout; blade linear (linear-lanceolate), 0.7–4 × 0.07–0.5 cm, coriaceous, base cuneate, margins plane, revolute on drying, apex acute or obtuse, 1-veined, surfaces hirtellous, laminar colleters absent. Inflores­cences solitary at nodes, 7–13-flowered; peduncle 0.1–2.7 cm, elongating somewhat in fruit, hirtellous; bracts caducous, 1, at base of each pedicel. Pedicels 5–8 mm, hirtellous. Flowers: calyx lobes linear to narrowly elliptic, 2–2.5 mm, apex obtuse, spreading, hirtellous, colleter 1, in sinuses, or absent; corolla green, cream, or pink, usually tinged pale to deep rose toward center of lobes, rotate-campanulate, tube 0.5–1 mm, lobes ascending, lanceolate to ovate, 3–4 mm, apex acute to obtuse, hirtellous abaxially, minutely hirtellous adax­ially, margins ciliate; corona ring cream or greenish cream, inflated corona segments adnate to corona ring, proximally green, distally glossy white, oblong, 1.5–2 mm; style apex shallowly convex. Follicles solitary or more commonly paired, lance-ovoid, 4–5.5 × 0.3–0.5 cm, apex long-attenuate, hirtellous to puberulent with curved trichomes. Seeds 10–20, light brown, narrowly winged, lenticular, lanceolate, 6–8 × 2.5–3 mm, convex face minutely papillate, flattened face coarsely papillate; coma white, 1.5–2 cm.

Flowering year round; fruiting May–Oct(–Nov). Arroyos, canyons, ravines, cliff bases, plains, gravel, sand, granite, gypsum, desert scrub; 30–900 m; Ariz., Calif., Nev.; Mexico (Baja California).

Funastrum hirtellum most closely resembles F. heterophyllum, with which it is sympatric over much of its range, occurring most commonly in desert arroyos. The hirtellous vestiture, smaller leaves, and corona lobes adnate to the ring distinguish F. hirtellum from F. heterophyllum, and no intermediates are known. Funastrum hirtellum is largely restricted to watersheds of the lower Colorado River in western Arizona, southeastern California, extreme southern Nevada, and extreme northern Baja California.