Asclepias longifolia
Asclepias rubra
Florida milkweed, long-leaf milkweed
red milkweed
1–few, spreading to decumbent, unbranched, 25–70 cm, puberulent with curved trichomes, not glaucous, rhizomes absent.
1, erect, unbranched, 40–110 cm, puberulent in a single line with curved trichomes to glabrate, somewhat 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, 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.
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, 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.
9–16 mm, puberulent with curved trichomes.
11–17 mm, puberulent on 1 side with curved trichomes.
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;
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.
ovate, 11–12 × 7–8 mm, margin winged, faces smooth;
coma 4–5 cm.
ovate, 7–9 × 5–7 mm, margin winged, faces minutely rugulose to smooth;
coma 2–5 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, narrowly fusiform, 7–12 × 1–1.5 cm, apex long-acuminate, smooth, sparsely puberulent with curved trichomes or pilosulous to glabrate.
Asclepias longifolia
Asclepias rubra
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.)
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.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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