Asclepias viridiflora
Asclepias quadrifolia
asclépiade à fleurs vertes, green antelopehorn milkweed, green comet milkweed, green milkweed
asclépiade à quatre feuilles, four-leaf milkweed
solitary, erect to ascending, unbranched (rarely), (10–)20–125 cm, puberulent with curved trichomes, not glaucous, rhizomes absent.
1, erect, unbranched, 25–60 cm, puberulent on 1 side with curved trichomes to glabrate, not 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, 2 mid-stem pairs usually with shortened internode forming a pseudo-whorl, petiolate, with 1 stipular colleter on each side of petiole;
petiole 2–7 mm, puberulent with curved trichomes;
blade ovate to elliptic, 2.5–12 × 1–6 cm, membranous, base cuneate, margins entire, apex acute to attenuate or acuminate, venation eucamptodromous, surfaces inconspicuously puberulent on veins with curved trichomes, margins ciliate, 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.
terminal, sometimes branched, and usually also extra-axillary at upper nodes, sessile or pedunculate, 7–31-flowered;
peduncle 0–3.5 cm, puberulent on 1 side with curved trichomes, with 1 caducous bract at the base of each pedicel.
7–13 mm, pilosulous.
17–28 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.
spreading to pendent;
calyx lobes lanceolate, 1.5–2 mm, apex acute, glabrous;
corolla pink or cream, lobes reflexed, elliptic, 4–5 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially;
gynostegial column 0.5–1.5 mm;
fused anthers tan to brown, cylindric, 1–1.5 mm, wings right-triangular, closed, apical appendages ovate;
corona segments pink or cream, sometimes striped pink dorsally, sessile, conduplicate, flattened dorsally, 2.5–4 mm, exceeding style apex, apex obtuse, oblique, glabrous, internal appendage subulate, exserted, arched to sharply inflexed over style apex, glabrous;
style apex shallowly depressed, cream to pale pink.
ovate, 7–8 × 4–5 mm, margin winged, faces minutely rugulose;
coma 2.5–3 cm.
ovate, 6–7 × 4–5 mm, margin winged, faces rugulose;
coma 3–4.5 cm.
erect on upcurved pedicels, fusiform to lance-ovoid, 6–10 × 1.5–2 cm, apex acuminate to attenuate, smooth, pilosulous.
erect on straight pedicels, narrowly fusiform, 8–16 × 0.4–1 cm, apex long-attenuate, smooth, sparsely puberulent with curved trichomes to glabrate.
= 22.
Asclepias viridiflora
Asclepias quadrifolia
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 quadrifolia is small statured compared to the other deciduous forest milkweeds. It is found predominantly on slopes of eroded, sedimentary rocks, especially cherty limestone. Like A. purpurascens, it is distributed primarily in the Appalachian and Ozark mountains. Populations with pinkish flowers are lovely in early spring; other populations have a more washed-out coloration. The characteristic pseudo-whorl of four mid-stem leaves is not always present. Like other forest milkweeds, it has experienced large population reductions at the northeastern margin of its range due to habitat loss. It is considered to be extirpated from Delaware and to be rare and of conservation concern in New Hampshire, Rhode Island (Providence County), and Ontario (Prince Edward County), as well as to the west in Kansas (Cherokee County). It has been reported, but not verified, from Minnesota. Putative hybrids with A. exaltata have been documented very rarely from the Appalachian Mountains and can be recognized by intermediate floral and vegetative traits.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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