Asclepias longifolia
Asclepias labriformis
Florida milkweed, long-leaf milkweed
Utah milkweed, Utah or labriform or Jones' or poison milkweed
1–few, spreading to decumbent, unbranched, 25–70 cm, puberulent with curved trichomes, not glaucous, rhizomes absent.
1–10, erect, unbranched (rarely distally), 15–70 cm, sparsely puberulent with curved trichomes to glabrate, not glaucous, rhizomatous.
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.
alternate (subopposite), sessile or petiolate, with 1 or 2 stipular colleters on each side of petiole plus 4–8 in axil;
petiole 0–7 mm, glabrous;
blade linear-lanceolate to lanceolate, often falcate, 6–14.5 × 0.5–2 cm, chartaceous, base cuneate, margins entire, apex attenuate to acute, mucronate, venation brochidodromous (often faintly), surfaces glabrous, midvein sometimes sparsely puberulent with curved trichomes abaxially, margins eciliate, 0–12 laminar colleters.
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.
extra-axillary, pedunculate, 6–28-flowered;
peduncle 0.2–2.5 cm, tomentose to glabrate, with 1 caducous bract at the base of each pedicel.
9–16 mm, puberulent with curved trichomes.
15–25 mm, tomentose to glabrate.
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 pendent;
calyx lobes lanceolate, 3–4 mm, apex acute, sparsely pilose or tomentulose to glabrate;
corolla ochroleucous, lobes reflexed, tips sometimes spreading, oval to elliptic, 6–7 mm, apex acute, glabrous abaxially, minutely hirtellous at base adaxially;
gynostegial column 1–1.5 mm;
fused anthers green to yellowish green, obconic, 1.5–2 mm, wings narrowly right-triangular, tip distended, closed, apical appendages ovate;
corona segments ochroleucous to cream, substipitate, conduplicate, dorsally rounded, nearly tubular, 2.5–3.5 mm, slightly exceeding style apex, apex truncate with proximal tooth on each side, glabrous, internal appendage falcate, exserted, sharply inflexed over style apex, glabrous;
style apex shallowly depressed, cream or green.
ovate, 11–12 × 7–8 mm, margin winged, faces smooth;
coma 4–5 cm.
ovate to oval, 12–13 × 8–9 mm, margin winged, faces obscurely rugulose to smooth;
coma 1.5–2 cm.
erect on upcurved pedicels, narrowly fusiform, 8–13.5 × 0.7–1.2 cm, apex attenuate, smooth, puberulent with curved trichomes.
pendulous on spreading to pendulous pedicels, ovoid, 3.5–5.5 × 1.2–2 cm, apex acuminate, smooth, tomentulose to glabrate.
Asclepias longifolia
Asclepias labriformis
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 labriformis is endemic to Utah (Emery, Garfield, Grand, Uintah, and Wayne counties) and is found in a remarkably narrow northeast–southwest band from the terraces surrounding the San Rafael Swell west of Green River, across Waterpocket Fold, to arroyo beds below the Kaiparowits Plateau southeast of Escalante. It shares pendulous follicles with several other milkweed species inhabiting sandy habitats, such as its close relative A. welshii, and more distant relatives A. cutleri and A. subulata. Asclepias labriformis is reputed to be one of the milkweeds that is most poisonous to livestock (J. M. Benson et al. 1979).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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