Asclepias macrotis
Asclepias tomentosa
long-hood milkweed, longhorn milkweed
tuba milkweed, velvetleaf milkweed
few–numerous, erect to ascending, branched at base, 10–35 cm, minutely puberulent with curved trichomes in a line to glabrate, not glaucous, rhizomatous.
solitary (rarely 2), erect, unbranched (rarely branched), 25–150 cm, densely puberulent with curved trichomes, not glaucous, rhizomes absent.
opposite, sessile, with 1 stipular colleter on each side of leaf base;
blade filiform, 2.5–7 × 0.05–0.15 cm, membranous, base cuneate, margins revolute, apex acute, mucronate, venation obscure, surfaces glabrous, margins minutely ciliate at base, laminar colleters absent.
opposite, petiolate, with 1 stipular colleter on each side of petiole;
petiole 2–9 mm, densely puberulent with curved trichomes;
blade lanceolate or ovate to oval or oblong or elliptic to oblanceolate or obovate, 3.5–10 × 1–5 cm, chartaceous, base obtuse to subcordate, margins crisped, apex acute or obtuse to truncate or emarginate, sometimes mucronate, venation eucamptodromous to brochidodromous, surfaces puberulent with curved trichomes to tomentulose, margins ciliate, 4–8 laminar colleters.
extra-axillary, sessile or pedunculate, 2–7-flowered;
peduncle 0–0.8 cm, puberulent with curved trichomes, with 1 caducous bract at the base of each pedicel.
extra-axillary, sessile or pedunculate, 5–37-flowered;
peduncle 0–0.3 cm, densely puberulent with curved trichomes to tomentulose, with 1 caducous bract at the base of each pedicel.
6–10 mm, minutely puberulent with curved trichomes in a line.
12–19 mm, densely pilose to tomentulose.
erect;
calyx lobes lanceolate, 2–2.5 mm, apex acute, glabrous;
corolla greenish cream tinged with red, lobes reflexed with spreading tips, oval, 4–5 mm, apex acute, glabrous;
gynostegial column 0.5–1 mm;
fused anthers brown, cylindric, 1–1.5 mm, wings right-triangular, closed, apical appendages broadly ovate;
corona segments cream to greenish cream, reddish brown at base or as a dorsal stripe, subsessile, conduplicate, 4–5 mm, exceeding style apex, apex truncate, long-caudate, crisped, with a proximal tooth on each side, hirtellous, internal appendage falcate, exserted, inflexed towards style apex, hirtellous;
style apex shallowly depressed, green.
erect;
calyx lobes lanceolate, 3–4 mm, apex acute, pilose;
corollas green, often tinged reddish or purplish, lobes reflexed with spreading tips, oval, 7–9 mm, apex acute, glabrous;
gynostegial column 0.5–1 mm;
fused anthers green, obconic, 3–4 mm, wings broadly right-triangular, closed, apical appendages broadly oval;
corona segments green with cream apex, often tinged pink or purple, stipitate, conduplicate, dorsally flattened, 3–4 mm, exceeded by style apex, apex truncate, glabrous, internal appendage falcate, exserted, sharply inflexed towards style apex, papillose;
style apex shallowly depressed, green, fading pink or red.
ovate, 6–8 × 2.5–4 mm, margin thickly winged, faces rugulose;
coma 2–2.5 cm.
ovate, 6.5–8 × 4.5–6 mm, margin winged, remotely erose, faces minutely and sparsely papillose and rugulose;
coma 3–3.5 cm.
erect on upcurved pedicels, fusiform, 4.5–6 × 0.5–0.7 cm, apex attenuate, smooth, glabrous.
erect on upcurved pedicels, fusiform to narrowly lance-ovoid, 9–18 × 1–1.5 cm, apex long-acuminate, smooth, puberulent with curved trichomes to pilosulous or tomentulose.
Asclepias macrotis
Asclepias tomentosa
With a suffruticose, cespitose, intricately branched habit, the only other milkweed with which Asclepias macrotis can be confused is the rarely encountered A. sperryi, which is restricted to the Big Bend region of Texas in the flora area. Although A. macrotis ranges across western Texas, it appears to be absent from Big Bend; no mixed populations of these species are known, and hybridization is neither known nor suspected. Its distribution in Colorado is limited to the southeastern corner of the state and in Oklahoma to the extreme tip of the Panhandle, in Cimarron County. In Arizona, it is more common but limited to the three southeastern counties: Cochise, Pima, and Santa Cruz. The elongate, curled apices of the corona segments are unique, and the small, drab flowers are quite elegant.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Asclepias tomentosa is restricted largely to coastal and inland sandhills. As described by B. A. Sorrie (2016), it exhibits a disjunct distribution, with gaps of unoccupied, but suitable, habitat in eastern Georgia and from the western Florida Panhandle to Louisiana. Sorrie reports a specimen from Alabama, but this cannot be found. When not in flower, A. tomentosa can be confused with A. curtissii in peninsular Florida, where they sometimes co-occur in close proximity, and with A. obovata on the Gulf Coastal Plain. It can be distinguished from A. curtissii by the usually larger and more densely vestitured leaf blades. Both species may have purple stems. Asclepias obovata can be distinguished from A. tomentosa by the hirtellous to velutinous vestiture of the herbage. Outside of Florida, populations of A. tomentosa are few, but it has not been considered to be of conservation concern; evaluation of its status in Texas and Georgia (known only from Coffee County) may be warranted.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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