Asclepias humistrata
pinewoods milkweed, sandhill milkweed, sandhill or pinewoods or pink-vein milkweed
1–10, decumbent or ascending to erect, unbranched, 20–50 cm, glabrous, glaucous, rhizomes absent.
opposite, sessile, with 0 or 1 stipular colleter on each side of leaf base;
blade ovate, 4–11 × 2.5–8 cm, subsucculent, base cordate, clasping, margins entire, apex obtuse, mucronulate, venation eucamptodromous to brochidodromous, surfaces glabrous, glaucous, laminar colleters absent.
terminal, sometimes branched, and extra-axillary at upper nodes, pedunculate, 7–37-flowered;
peduncle 2.6–5.5 cm, glabrous, glaucous, with 1 bract at the base of each pedicel.
18–26 mm, glabrous.
erect to spreading;
calyx lobes lanceolate, 2–3 mm, apex obtuse, glabrous;
corolla pink or red to pinkish green or reddish green, lobes reflexed, sometimes with spreading tips, oval, 5.5–6 mm, apex acute to obtuse, glabrous;
gynostegial column 0.5–1 mm;
fused anthers brown, cylindric, 1.2–1.5 mm, wings right-triangular, tips closed, apical appendages broadly ovate;
corona segments pink to nearly white at base, white at apex, yellowing with age, sessile, conduplicate, dorsally rounded, 3–3.5 mm, slightly exceeding style apex, base subsaccate, apex truncate with a proximal tooth on each side, glabrous, internal appendage ensiform, slightly incurved, slightly exserted, glabrous;
style apex shallowly depressed, pink.
ovate to oval, 8–8.5 × 5–6 mm, margin winged, faces papillose-rugulose;
coma 3–3.5 cm.
erect on upcurved pedicels, lance-ovoid, 8–12 × 0.8–1.7 cm, apex long-acuminate to attenuate, smooth, glabrous, glaucous.
Asclepias humistrata
Asclepias humistrata is a distinctive milkweed unlike any other in its range. Its decumbent habit with vertically oriented leaves, bearing strongly contrasting white or pink venation, is unmatched by any other sandhill species. It is apparently closely related to the highly disjunct A. cordifolia of the Pacific Northwest, suggesting an unusual biogeographic history (M. Fishbein et al. 2011). It shares with this species bluish, grayish, or purplish glaucous herbage. Asclepias humistrata often exhibits remarkably high fruit set and, perhaps as a consequence, often grows in large, dense populations. It is reported as possibly extirpated from Louisiana, where it was documented from Washington Parish. Asclepias amplexicaulis Michaux, an illegitimate synonym, created confusion between this species and A. amplexicaulis Smith, a similarly glaucous, cordate-leaved species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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