Asclepias viridiflora
Asclepias rubra
asclépiade à fleurs vertes, green antelopehorn milkweed, green comet milkweed, green milkweed
red milkweed
solitary, erect to ascending, unbranched (rarely), (10–)20–125 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 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, 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.
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.
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.
7–13 mm, pilosulous.
11–17 mm, puberulent on 1 side with curved trichomes.
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 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, 7–8 × 4–5 mm, margin winged, faces minutely rugulose;
coma 2.5–3 cm.
ovate, 7–9 × 5–7 mm, margin winged, faces minutely rugulose to smooth;
coma 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, narrowly fusiform, 7–12 × 1–1.5 cm, apex long-acuminate, smooth, sparsely puberulent with curved trichomes or pilosulous to glabrate.
= 22.
Asclepias viridiflora
Asclepias rubra
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.)
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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