Asclepias viridiflora
Asclepias linaria
asclépiade à fleurs vertes, green antelopehorn milkweed, green comet milkweed, green milkweed
hierba del cuervo, needle leaf milkweed, pineneedle milkweed
solitary, erect to ascending, unbranched (rarely), (10–)20–125 cm, puberulent with curved trichomes, not glaucous, rhizomes absent.
few–numerous, erect, branched, especially distally, 30–70 cm, woody, bark brown to gray, twigs puberulent with curved trichomes, 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.
eventually caducous, alternate, spiral to irregular, sessile, with 1 stipular colleter on each side of leaf base;
blade linear, needlelike, 1.5–4 × 0.1–0.15 cm, chartaceous, base cuneate, margins revolute, apex acute, mucronate, venation obscure, sparsely pilosulous to glabrate, 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 or pedunculate, 9–30-flowered;
peduncle 0–2.5 cm, puberulent with curved trichomes to pilosulous, with 1 caducous bract at the base of each pedicel.
7–13 mm, pilosulous.
10–14 mm, pilosulous.
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 to pendent;
calyx lobes lanceolate to ovate, 2–3 mm, apex acute, sparsely pilosulous to glabrate;
corolla green to cream, often tinged red or purple, lobes reflexed with spreading tips, elliptic, 3.5–5 mm, apex acute, glabrous abaxially, minutely hirtellous at base adaxially, 1 margin ciliate;
gynostegial column 0.2–0.5 mm;
fused anthers brown, obconic, 1–1.5 mm, wings right-triangular, closed, apical appendages ovate, erose;
corona segments cream, sometimes with greenish or purplish dorsal stripe, subsessile or sessile, cupulate, 2.5–3 mm, exceeding style apex, apex obtuse to rounded, glabrous, internal appendage rod-shaped, slightly exserted, glabrous;
style apex shallowly depressed, green.
ovate, 7–8 × 4–5 mm, margin winged, faces minutely rugulose;
coma 2.5–3 cm.
naviculate, ovate, 5–6 × 3–4 mm, margin very narrowly winged, faces rugulose, the concave one conspicuously so;
coma 1.5–2 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, ovoid, 3.5–5 × 0.6–1 cm, apex acuminate, smooth, glabrous.
= 22.
= 22.
Asclepias viridiflora
Asclepias linaria
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 linaria is arguably the most distinctive milkweed species in the Americas. It is the only species with woody stems and the only one to form hemispherical shrubs with needlelike leaves. Small plants with few stems are easily mistaken for seedling conifers. This species is widespread and occupies a great variety of habitats in Mexico. It enters the flora area in southeastern Arizona and in southwestern New Mexico only in the Peloncillo Mountains (Hidalgo County); its occurrence in the flora area is evidently relictual. In the region, it is restricted to lower reaches of protected canyons that ameliorate aridity and freezing temperatures, sites that harbor other tropical and subtropical species reaching their northern limits. The plants are often quite floriferous and attract an abundance of Hymenoptera, Lepidoptera, and Diptera.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local Web sites:
Go Botany, 
IL Wildflowers, 
KS Wildflowers, 
LA Plants, 
MD Biodiversity, 
MI Flora, 
MN Wildflowers, 
MO Plants, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
