Short-crowned or shortcrown milkweed

Herbs. Stems 4–25, erect, unbranched or branched near base, 20–40 cm, tomentulose, not glaucous, rhizomes absent. Leaves opposite to subopposite, petiolate, with 1 or 2 stipular colleters on each side of petiole; petiole 2–8 mm, tomentulose; blade linear-lanceolate, 5–15 × 0.3–1.3 cm, chartaceous, base cuneate to rounded, mar­gins often obscurely crisped, apex acute, mucronate, vena­tion brochidodromous, surfaces tomentulose to glabrate, midvein puberulent with curved trichomes, margins minutely ciliate, laminar colleters absent. Inflo­rescences extra-axillary, pedunculate, 4–15-flowered; peduncle 0.2–1.5 cm, tomentose, with 1 caducous bract at the base of each pedicel. Pedicels 9–15 mm, tomentose. Flowers erect; calyx lobes ovate-lanceolate, 2–3 mm, apex acute, tomentulose; corolla red-violet, sometimes green with red tinge, lobes reflexed, ovate, 4–6 mm, apex acute, minutely pilosulous; gynostegium subsessile; fused anthers brown, cylindric, 2–2.5 mm, wings right-triangular, closed, apical appendages ovate; corona segments red-violet to pink basally, white apically, sessile, tubular, 1.5–2 mm, greatly exceeded by style apex, apex truncate, oblique, with a proximal tooth on each side, glabrous, internal appendage lingulate, slightly exserted, sharply inflexed towards gynostegium, glabrous; style apex shallowly depressed, red-violet. Follicles erect on upcurved pedicels, lance-ovoid, 5–7 × 1.2–1.8 cm, apex acuminate, shallowly ribbed, conspic­uously striate, tomentulose. Seeds oval to ovate, 6–7 × 4–6 mm, margin winged, faces papillate-tomentulose with dendritic scales; coma 2–2.5 cm.

Flowering Apr–Sep(–Oct); fruiting (May–)Jun–Oct. Plains, bajadas, pastures, arroyos, stream banks, ripar­ian areas, limestone, igneous substrates, alluvium, gravel, clay, silty, and sandy soils, desert grasslands, desert scrub, oak-juniper, juniper, and mesquite woodlands; 900–1900 m; Ariz., N.Mex., Tex.; Mexico (Aguascalientes, Chihuahua, Coahuila, Durango, Nuevo León, Sonora, Zacatecas).

Asclepias brachystephana is a blue-gray, bushy herb with ascending foliage, few-flowered umbels of small, red and white flowers, and conspicuously striped fol­licles. It is unlike any other milkweed. Nonetheless, herbarium specimens are commonly confused with those of A. asperula because the herbage of A. brachystephana turns green on drying, and the leaves of A. asperula subsp. asperula are often of similar size and shape. However, leaf arrangement in A. asperula is alternate rather than opposite. The flowers of A. brachystephana are remarkably similar to, and convergent with, those of A. cutleri, A. eastwoodiana, A. ruthiae, A. sanjuanensis, and A. uncialis (M. Fishbein et al. 2011). In Arizona, A. brachystephana is restricted to the portion of the southeastern corner of the state with Chihuahuan floris­tic affinities, in Cochise, Graham, Pima, and Santa Cruz counties.