Asclepias viridiflora
Asclepias sperryi
asclépiade à fleurs vertes, green antelopehorn milkweed, green comet milkweed, green milkweed
sperry's milkweed
solitary, erect to ascending, unbranched (rarely), (10–)20–125 cm, puberulent with curved trichomes, not glaucous, rhizomes absent.
few–numerous, erect to ascending, branched at base, 5–20 cm, minutely puberulent with curved trichomes to glabrate, not glaucous, rhizomatous.
opposite to subopposite, sessile or petiolate, with 1 or 2 stipular colleters on each side of petiole and also in axil;
petiole 0–5 mm, puberulent with curved trichomes;
blade linear to broadly oval or nearly orbiculate, 2–13 × 0.8–6 cm, chartaceous, base cuneate to rounded, margins entire or crisped, apex acute or obtuse to truncate or emarginate, mucronate, venation brochidodromous, surfaces sparsely pilosulous to glabrate, margins ciliate, laminar colleters absent.
opposite, sessile, with 1 stipular colleter on each side of leaf base;
blade filiform, 2–5 × 0.05–0.1 cm, membranous, base cuneate, margins revolute, apex acute, mucronate, venation obscure, surfaces glabrous, margins minutely ciliate at base, laminar colleters absent.
extra-axillary at upper nodes, sometimes branched at peduncle apex, sessile or pedunculate, 22–60-flowered;
peduncle 0–4 cm, puberulent with curved trichomes to pilosulous, with 1 caducous bract at the base of each pedicel.
extra-axillary, sessile, 1–2-flowered, with 1 caducous bract at the base of each pedicel.
7–13 mm, pilosulous.
4–10 mm, minutely puberulent with curved trichomes in a line.
erect to pendent;
calyx lobes narrowly lanceolate, 2–3 mm, apex acute, pilosulous;
corolla green to yellowish green, sometimes tinged red, lobes reflexed, oblong, 5–7 mm, apex acute, inconspicuously pilosulous at apex abaxially, glabrous adaxially;
gynostegium sessile;
fused anthers green, cylindric, 3–4 mm, wings triangular, widest at middle, closed, apical appendages ovate, marginally inflexed, apically deflexed;
corona segments green to cream, sometimes tinged red, sessile, laminar, margins incurved, appressed to column, 3–4 mm, greatly exceeded by style apex, apex obtuse, glabrous, internal appendage absent or obscure, glabrous;
style apex shallowly depressed, green.
erect;
calyx lobes ovate, 2–3 mm, apex acute, glabrous;
corolla pale greenish yellow tinged with purple, lobes spreading, ovate, 4–5 mm, apex acute, glabrous;
gynostegium sessile;
fused anthers brown, cylindric, 1.5–2 mm, wings deltoid, apical appendages broadly ovate;
corona segments pale greenish yellow to white (sometimes tinted purple), sessile, chute-shaped, sharply inflexed, 2–3 mm, equaling to exceeded by style apex, apex truncate, subcaudate, hirtellous, internal appendage an included crest, hirtellous;
style apex shallowly depressed, green.
ovate, 7–8 × 4–5 mm, margin winged, faces minutely rugulose;
coma 2.5–3 cm.
ovate, 5–6 × 3–4 mm, margin thickly winged, faces rugulose;
coma 2–2.5 cm.
erect on upcurved pedicels, fusiform to lance-ovoid, 6–10 × 1.5–2 cm, apex acuminate to attenuate, smooth, pilosulous.
erect on upcurved pedicels, fusiform, 5–7 × 0.5–0.7 cm, apex attenuate, smooth, glabrous.
= 22.
Asclepias viridiflora
Asclepias sperryi
Asclepias viridiflora is one of the milkweeds with spherical, greenish umbels and inconspicuous coronas (see also A. engelmanniana, A. hirtella, A. lanuginosa, A. longifolia, A. rusbyi, A. stenophylla). Prior to close examination, the tight green balls of open flowers appear to be merely in bud. The diversity in leaf morphology among individuals (linear to orbiculate) is remarkable, but has no taxonomic significance—the full range of variation may be found within single populations. This is the most widespread milkweed within the flora area, ranging across most of the United States (absent only from the westernmost states and most of New England) and southern Canada. It is nowhere abundant, but may be regularly encountered in suitable, thin-soiled prairie habitats, especially in the Great Plains. It is rare and considered to be of conservation concern on the margins of its range, in Alberta (Cypress, Forty Mile, and Warner counties), Arizona (Coconino, Gila, and Yavapai counties), Connecticut (New Haven County), Florida (Gadsden and Jackson counties), and New York (Columbia, Nassau, Richmond, and Suffolk counties).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Asclepias sperryi is one of the least known milkweeds. It is exceedingly cryptic and easily mistaken for a small clump of grass, perhaps of Bouteloua; it is likely to be far more common than documented. However, very few observations or collections have been made in recent decades, and conservation assessment is warranted. Its range is restricted to limestone mountains of the Chihuahuan Desert in the Big Bend region of Texas, in Brewster and Pecos counties, and adjacent areas of Coahuila, entirely within the range of its sister species, A. macrotis. It is the only species of Asclepias that regularly produces a single flower per umbel.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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