Herbs. Stems 1–12, erect, unbranched to moderately branched below, 10–30 cm, puberulent with curved tri­chomes, not glaucous, rhizom­atous. Leaves alternate, sessile, with 1 stipular colleter on each side of leaf base; blade needlelike to narrowly linear, 2.5–5.5 × 0.05–0.1 cm, chartaceous, base cuneate, margins entire, apex acute, mucronate, venation obscure, surfaces glabrous, mar­gins ciliate, laminar colleters absent. Inflorescences extra-axillary at upper nodes, sometimes appearing terminal, pedunculate, 3–13-flowered; peduncle 0.1–2 cm, puberu­lent with curved trichomes, with 1 caducous bract at the base of each pedicel. Pedicels 6–16 mm, puberulent with curved trichomes. Flowers erect; calyx lobes narrowly lanceolate, 2–3 mm, apex acute, puberulent with curved trichomes to glabrate; corolla pink to cream with a pink tinge, lobes reflexed with spreading tips, elliptic, 3.5–4.5 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially; gynostegial column 0.8–1 mm; fused anthers green, columnar, 1–1.5 mm, wings narrowly right-triangular, closed, apical appendages deltoid; corona segments cream, sometimes tinged or striped pink, stipitate, tubular, dorsally flattened, 2–2.5 mm, exceeded by to equaling style apex, apex obtuse, glabrous, internal appendage acicular, exserted, arching towards style apex, glabrous; style apex shallowly depressed, cream. Follicles erect on straight pedicels, narrowly fusiform, 2.5–9.5 × 0.5–1 cm, apex acuminate to attenuate, smooth, minutely puberulent with curved trichomes to glabrate. Seeds ovate, 5–6 × 3–5 mm, margin winged, faces smooth; coma 2–3 cm.

Phenology: Flowering (May–)Jun–Sep; fruiting Aug–Oct.
Habitat: Slopes, bluffs, plains, sandhills, dunes, rock outcrops, playas, ditches, basalt, alluvium, sandy, clay, rocky, and gravel soils, prairies, meadows, shrubby grasslands, pine woodlands.
Elevation: 600–2300 m.

Distribution

• Generated Map
• Legacy Map

Colo., Kans., Mont., Nebr., N.Mex., N.Dak., Okla., S.Dak., Tex., Wyo.

Discussion

Asclepias linaria and A. pumila of southeastern Arizona and extreme southwestern New Mexico are the only milkweeds with densely spiraled, linear to needlelike leaves. Hybrids with A. subverticillata and A. verticillata have been documented; see discussion under these species. When not flowering, A. pumila is cryptic and easily overlooked in its grassland habitat, especially when growing among Bouteloua species. Specimens supposedly from Illinois and Arizona (C. Mohr [US]) undoubtedly have incorrect label data. A population in the Sacramento Mountains of southern New Mexico (Otero County) appears to be a significant southern disjunction.

Selected References

None.

Lower Taxa

None.