Texas milkweed

Asclepias perennis Walter var. parvula A. Gray

Subshrubs or herbs. Stems 1–numerous, erect, sparsely to moderately branched in upper half, 25–90 cm, puberulent with curved trichomes in a line, not glaucous, rhizomes absent. Leaves opposite, peti­olate, with 1 or 2 stipular colleters on each side of petiole on a cil­iate interpetiolar ridge; petiole 5–20 mm, puberulent with curved trichomes; blade ovate to lanceolate or elliptic, 2–7 × 0.5–3 cm, chartaceous, base cuneate to obtuse, margins entire, apex acute to acuminate, venation eucamptodromous, surfaces puberulent with curved trichomes on veins abaxially, sparsely puberulent with curved trichomes on veins to glabrate adaxially, margins ciliate, laminar colleters absent. Inflorescences extra-axillary at upper nodes, some appearing terminal, pedunculate, 14–31-flowered; peduncle 0.9–3 cm, puber­ulent with curved trichomes in a line, with 1 caducous bract at the base of each pedicel. Pedicels 7–14 mm, puberulent with curved trichomes in a line. Flowers erect; calyx lobes narrowly lanceolate, 1.5–2 mm, apex acute, puberulent with curved trichomes; corolla white, sometimes tinged green, lobes reflexed with spreading tips, elliptic, 3.5–5 mm, apex acute to obtuse, glabrous abaxially, minutely papillose at base adaxially; gynostegial column 1–1.5 mm; fused anthers brown, columnar, 1.5–2 mm, wings narrowly right-triangular, closed, apical appendages deltoid; corona segments white, sometimes tinged pink, stipitate, cupu­late, dorsally rounded, 2–3 mm, equaling to slightly exceeding style apex, apex obtuse, glabrous, internal appendage acicular, exserted, arching over style apex, glabrous; style apex shallowly depressed, white. Follicles erect on straight pedicels, narrowly fusiform, 9–13 × 0.5–1 cm, apex long-acuminate to attenuate, smooth, glabrous. Seeds ovate, 6–7 × 4–5 mm, margin winged, faces smooth or sparsely papillose; coma 2–3 cm.

Flowering May–Sep; fruiting (Jul–)Aug–Oct. Can­yons, arroyos, slopes, cliff bases, bluffs, streamsides, limestone, igneous rocks, rocky and clay soils, riparian, oak-juniper, and oak woods, pine-oak forest; 300–2000 m; Tex.; Mexico (Coahuila, Nuevo León).

In the flora area, Asclepias texana has a disjunct distribution on the Edwards Plateau and in the mountains of the Big Bend region. Although commonly occurring in canyons and riparian areas, A. texana is quite drought tolerant in cultivation. The tidy, bushy habit, long flowering stems topped by bright white spherical umbels, and rapid growth from seed make this a suitable candidate for horticultural use. It is known to be hardy to at least USDA Zone 7.