Asclepias scaposa

Herbs. Stems 1–5+, erect, unbranched (rarely at base), 15–20 cm, pilosulous, not glaucous, rhizomes absent. Leaves opposite, sessile or petiolate, with 1 stipular colleter on each side of petiole; petiole 0–6 mm, pilosulous to glabrate; blade oval to elliptic, 6–8 × 1.5–2.5 cm, membranous, base cuneate, margins crisped, apex obtuse to acute, venation eucamptodromous, surfaces sparsely hirtellous, margins ciliate, laminar colleters absent. Inflorescences terminal, solitary, pedunculate, 15–30-flowered; peduncle 7–17 cm, pilose, bracts absent or few. Pedicels 15–20 mm, pilose. Flowers erect to pendent; calyx lobes narrowly lanceolate, 2–2.5 mm, apex acute, pilose; corolla green with purplish tinge (reddish purple), lobes reflexed, elliptic, 4–5 mm, apex acute, glabrous; gynostegial column 0.5–1 mm; fused anthers brown, cylindric, 1.5–2 mm, wings curved, wider at base, apical appendages ovate; corona segments cream, sometimes yellow- or red-tinged or yellow or red at base, sessile, tubular, 2–3 mm, exceeding style apex, base saccate, apex truncate, dentate, glabrous, internal appendage falcate, exserted, arching above style apex, glabrous; style apex shallowly depressed, green or cream. Follicles erect on upcurved pedicels, fusiform, 5–6 × 1–1.5 cm, apex long-acuminate, smooth, pilosulous. Seeds not seen.

Phenology: Flowering Mar–Aug; fruiting May.
Habitat: Ridges, slopes, limestone, rocky, silty, and clay soils, pine-oak woodlands, desert scrub, thorn scrub.
Elevation: 600–2000 m.

Tex., Mexico (Coahuila, Nuevo León, San Luis Potosí, Zacatecas).

Discussion

The long-pedunculate, terminal inflorescence combined with short stature is distinctive in Asclepias scaposa. Although the locality of one of the syntypes was attributed to New Mexico by E. L. Greene, that is the only report for that state. Both syntypes were collected by Charles Wright for the United States-Mexico boundary survey, but neither of his labels indicates that they were collected in New Mexico. It is very likely that both collections were made in Texas or northeastern Mexico, and New Mexico is excluded from the distribution here. The common name Bear Mountain milkweed may refer to a ridge in the northwestern portion of the Davis Mountains, although no collections are known from this area. The few collections and observations that have been made in Texas are from scattered locations in Brewster, Crockett, Pecos, Presidio, Reeves, and Terrell counties, and conservation status in the United States merits assessment. In Mexico, A. scaposa also has been rarely collected, except for a local area in Nuevo León (Municipio de Galeana).

Selected References

None.

Lower Taxa