Asclepias longifolia
Asclepias nyctaginifolia
Florida milkweed, long-leaf milkweed
Mohave milkweed, Mojave milkweed
1–few, spreading to decumbent, unbranched, 25–70 cm, puberulent with curved trichomes, not glaucous, rhizomes absent.
1–10, spreading or decumbent to erect, unbranched or rarely branched near base, 15–40 cm, puberulent with curved trichomes or hirtellous, 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.
persistent or gradually caducous from base, opposite, petiolate, with 1 or 2 stipular colleters on each side of petiole plus 0–4 in axil;
petiole 6–25 mm, puberulent with curved trichomes to hirtellous;
blade ovate to lanceolate, 4.5–15 × 1.5–7.5 cm, chartaceous, base cuneate or obtuse to truncate or subcordate, margins sometimes crisped, apex obtuse to acute, venation eucamptodromous to faintly brochidodromous, surfaces hirtellous, rarely conduplicate, 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, sessile or pedunculate, 5–28-flowered;
peduncle 0–1 cm, hirtellous, with 1 caducous bract at the base of each pedicel.
9–16 mm, puberulent with curved trichomes.
17–30 mm, hirtellous.
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, 3–5 mm, apex acute, hirtellous;
corolla green, sometimes tinged reddish or purplish abaxially, lobes reflexed, elliptic to lanceolate, 9–13 mm, apex acute, minutely hirtellous throughout or glabrous at tips abaxially, glabrous adaxially;
gynostegial column 0.3–0.5 mm;
fused anthers brown, obconic, 1.7–2 mm, wings triangular, widest at middle, closed, apical appendages ovate;
corona segments cream to green with cream apex, fading yellow, sessile, tubular, slightly sinuous, relatively stout, 8–11 mm, greatly exceeding style apex, apex slightly flared, truncate, minutely papillose to glabrate, internal appendage lingulate, sharply incurved, barely exserted, greatly exceeded by segment margin and exposing cavity, minutely papillose.
ovate, 11–12 × 7–8 mm, margin winged, faces smooth;
coma 4–5 cm.
ovate to oval, 6–8 × 4.5–6.5 mm, margin winged, faces smooth;
coma 2–4 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, 6.5–10 × 1.5–3 cm, apex acuminate, smooth, sometimes faintly striate, puberulent with curved trichomes or hirtellous.
Asclepias longifolia
Asclepias nyctaginifolia
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 nyctaginifolia is a western counterpart of the more widespread A. oenotheroides and differs primarily in larger leaves and more robust corona segments. Differences are discussed under the latter species. The most widely used common name, Mohave milkweed, is somewhat misleading as the species is mainly distributed along the northern and eastern margins of the Sonoran Desert and barely enters the Mohave Desert. The species is common throughout the southwestern half of Arizona and is rare in California (San Bernardino County), Nevada (Clark County), and New Mexico (Catron, Grant, and Hidalgo counties).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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