Asclepias longifolia
Asclepias humistrata
Florida milkweed, long-leaf milkweed
pinewoods milkweed, sandhill milkweed, sandhill or pinewoods or pink-vein milkweed
1–few, spreading to decumbent, unbranched, 25–70 cm, puberulent with curved trichomes, not glaucous, rhizomes absent.
1–10, decumbent or ascending to erect, unbranched, 20–50 cm, glabrous, glaucous, rhizomes absent.
opposite or alternate, sessile or petiolate, with 1 or 2 stipular colleters on each side of petiole, also in axil;
petiole 0–2 mm, puberulent with curved trichomes;
blade linear to linear-lanceolate, 5–18 × 0.2–1 cm, chartaceous, base cuneate, margins entire, apex acute to attenuate, sometimes mucronate, venation brochidodromous, surfaces scabridulous to puberulent with curved trichomes, especially on veins, margins ciliate, laminar colleters 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 and extra-axillary at upper nodes, sessile or pedunculate, 13–28(–36)-flowered;
peduncle 0–6 cm, puberulent with curved trichomes, with 1 caducous bract at the base of each pedicel.
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.
9–16 mm, puberulent with curved trichomes.
18–26 mm, glabrous.
erect to spreading;
calyx lobes narrowly lanceolate, 1.5–2 mm, apex acute, puberulent with curved trichomes;
corolla white to greenish cream, purple at lobe tips, lobes reflexed, oblong, 3–5 mm, apex obtuse, glabrous;
gynostegial column 0.2–0.5 mm;
fused anthers green or brown, cylindric, 1–1.5 mm, wings triangular to trapezoidal, widest at middle, slightly open at tip, apical appendages ovate;
corona segments pinkish lavender to red-violet, often with white apex, often a darker red-violet stripe or at base, sessile, laminar, strongly dorsally compressed, margins incurved, appressed to column, curved to subsaccate, 2–2.5 mm, exceeding point of anther wings, greatly exceeded by style apex, apex obtuse to truncate, glabrous, internal appendage absent or obscure, glabrous;
style apex shallowly depressed, greenish cream to green.
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, 11–12 × 7–8 mm, margin winged, faces smooth;
coma 4–5 cm.
ovate to oval, 8–8.5 × 5–6 mm, margin winged, faces papillose-rugulose;
coma 3–3.5 cm.
erect on upcurved pedicels, narrowly fusiform, 8–13.5 × 0.7–1.2 cm, apex attenuate, smooth, puberulent with curved trichomes.
erect on upcurved pedicels, lance-ovoid, 8–12 × 0.8–1.7 cm, apex long-acuminate to attenuate, smooth, glabrous, glaucous.
Asclepias longifolia
Asclepias humistrata
Asclepias longifolia has sometimes been treated to include A. hirtella as conspecific, as discussed under that species. As circumscribed here, the distribution of A. longifolia extends along the Atlantic Coastal Plain south of Delaware to Florida and westward to the Mississppi River. Reports of A. longifolia from west of the Mississippi River in Louisiana and in Texas are assigned here to A. hirtella. Hence, the range of A. longifolia in Louisiana is extremely limited, and the conservation status of this species warrants assessment in that state (Livingston, Saint Helena, Saint Tammany, Tangipahoa, and Washington parishes). Reports of A. longifolia from Maryland and West Virginia have not been confirmed, and the species is considered extirpated from Delaware. Otherwise, it is rare at the northern extent of its range and considered to be of conservation concern in North Carolina and Virginia (Greensville and Prince George counties).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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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