Asclepias rubra

Herbs. Stems 1, erect, unbranched, 40–110 cm, puber­ulent in a single line with curved trichomes to glabrate, somewhat glaucous, rhizomes absent. Leaves opposite, petiolate, with 1 stipular colleter on each side of petiole on a ciliate interpetiolar ridge; petiole 1–2 mm, glabrous; blade narrowly lance­olate to ovate, 5–16 × 1–4.5 cm, chartaceous, base cor­date, margins entire, apex attenuate, venation brochi­dodromous, surfaces glabrous, somewhat glaucous, margins ciliate, 6–8 laminar colleters, usually obscured by conduplicate petiole. Inflorescences terminal, usually branched, sometimes also extra-axillary at 1 upper node, pedunculate, 9–20-flowered; peduncle 0.5–13 cm, puberulent in 1 line with curved trichomes, with 1 caducous bract at the base of each pedicel. Pedicels 11–17 mm, puberulent on 1 side with curved trichomes. Flowers erect; calyx lobes lanceolate, 2–2.5 mm, apex acute, glabrous; corolla pink to reddish purple, lobes reflexed with spreading tips, elliptic, 7–9 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially; gynostegial column 1.5–2 mm; fused anthers green, cylindric, 2–2.5 mm, wings right-triangular, closed, apical appendages broadly ovate; corona segments pink to lavender, stipitate, conduplicate, dor­sally flattened, 6–7 mm, greatly exceeding style apex, apex acute, glabrous, internal appendage subulate, exserted, arching above style apex, glabrous; style apex shallowly depressed, green. Follicles erect on upcurved pedicels, narrowly fusiform, 7–12 × 1–1.5 cm, apex long-acuminate, smooth, sparsely puberulent with curved trichomes or pilosulous to glabrate. Seeds ovate, 7–9 × 5–7 mm, margin winged, faces minutely rugulose to smooth; coma 2–5 cm.

Phenology: Flowering Apr–Sep; fruiting Jul–Oct.
Habitat: Streamsides, bogs, baygalls, swales, saturated soils, pine flatwoods, savannas, riparian woods, thickets.
Elevation: 0–300 m.

Distribution

• Generated Map
• Legacy Map

Ala., Del., D.C., Fla., Ga., La., Md., Miss., N.J., N.Y., N.C., Pa., S.C., Tex., Va.

Discussion

Distinguishing features and hybridization of Asclepias rubra and A. lanceolata are discussed under the latter species. The common name red milkweed is a misnomer, as the flowers are actually more commonly shades of pink or purple, whereas the similar A. lanceolata often has truly red corollas. Asclepias rubra is less common than A. lanceolata and considered to be of greater conservation concern in Alabama, Delaware, Georgia, Maryland, New Jersey, and Virginia. It is considered to be extirpated from the District of Columbia, New York, and Pennsylvania. It also has been reported from Arkansas, but this remains unconfirmed and must be considered unlikely.

Selected References

None.

Lower Taxa

None.