Asclepias viridiflora |
Asclepias humistrata |
|
---|---|---|
asclépiade à fleurs vertes, green antelopehorn milkweed, green comet milkweed, green milkweed |
pinewoods milkweed, sandhill milkweed, sandhill or pinewoods or pink-vein milkweed |
|
Habit | Herbs. | Herbs. |
Stems | solitary, erect to ascending, unbranched (rarely), (10–)20–125 cm, puberulent with curved trichomes, not glaucous, rhizomes absent. |
1–10, decumbent or ascending to erect, unbranched, 20–50 cm, glabrous, glaucous, rhizomes absent. |
Leaves | 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 0 or 1 stipular colleter on each side of leaf base; blade ovate, 4–11 × 2.5–8 cm, subsucculent, base cordate, clasping, margins entire, apex obtuse, mucronulate, venation eucamptodromous to brochidodromous, surfaces glabrous, glaucous, laminar colleters absent. |
Inflorescences | 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 extra-axillary at upper nodes, pedunculate, 7–37-flowered; peduncle 2.6–5.5 cm, glabrous, glaucous, with 1 bract at the base of each pedicel. |
Pedicels | 7–13 mm, pilosulous. |
18–26 mm, glabrous. |
Flowers | 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 spreading; calyx lobes lanceolate, 2–3 mm, apex obtuse, glabrous; corolla pink or red to pinkish green or reddish green, lobes reflexed, sometimes with spreading tips, oval, 5.5–6 mm, apex acute to obtuse, glabrous; gynostegial column 0.5–1 mm; fused anthers brown, cylindric, 1.2–1.5 mm, wings right-triangular, tips closed, apical appendages broadly ovate; corona segments pink to nearly white at base, white at apex, yellowing with age, sessile, conduplicate, dorsally rounded, 3–3.5 mm, slightly exceeding style apex, base subsaccate, apex truncate with a proximal tooth on each side, glabrous, internal appendage ensiform, slightly incurved, slightly exserted, glabrous; style apex shallowly depressed, pink. |
Seeds | ovate, 7–8 × 4–5 mm, margin winged, faces minutely rugulose; coma 2.5–3 cm. |
ovate to oval, 8–8.5 × 5–6 mm, margin winged, faces papillose-rugulose; coma 3–3.5 cm. |
Follicles | erect on upcurved pedicels, fusiform to lance-ovoid, 6–10 × 1.5–2 cm, apex acuminate to attenuate, smooth, pilosulous. |
erect on upcurved pedicels, lance-ovoid, 8–12 × 0.8–1.7 cm, apex long-acuminate to attenuate, smooth, glabrous, glaucous. |
2n | = 22. |
|
Asclepias viridiflora |
Asclepias humistrata |
|
Phenology | Flowering Apr–Sep(–Oct); fruiting Jun–Nov. | Flowering (Feb–)Mar–Oct; fruiting (Mar–)Apr–Oct(–Nov). |
Habitat | Slopes, ridges, bluffs, flats, canyons, arroyos, glades, fields, meadows, pastures, sandhills, dunes, pond edges, streamsides, playas, sandstone, limestone, gypsum, serpentine, dolomite, alluvium, silty, sandy, clay, rocky, and calcareous soils, prairies, desert grasslands, oak scrub, oak, oak-juniper, oak-hickory, pine-oak, and pine woodlands, forest openings and edges. | Dunes, sandhills, ridges, slopes, coastal strand, streamsides, sandy soils, pine flatwoods, pine-oak woods, oak and pine-oak scrub. |
Elevation | 0–2300 m. (0–7500 ft.) | 0–200 m. (0–700 ft.) |
Distribution |
AL; AR; AZ; CO; CT; DC; DE; FL; GA; IA; IL; IN; KS; KY; LA; MD; MI; MN; MO; MS; MT; NC; ND; NE; NJ; NM; NY; OH; OK; PA; SC; SD; TN; TX; VA; WI; WV; WY; AB; MB; ON; SK; Mexico (Coahuila)
|
AL; FL; GA; LA; MS; NC; SC
|
Discussion | 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 humistrata is a distinctive milkweed unlike any other in its range. Its decumbent habit with vertically oriented leaves, bearing strongly contrasting white or pink venation, is unmatched by any other sandhill species. It is apparently closely related to the highly disjunct A. cordifolia of the Pacific Northwest, suggesting an unusual biogeographic history (M. Fishbein et al. 2011). It shares with this species bluish, grayish, or purplish glaucous herbage. Asclepias humistrata often exhibits remarkably high fruit set and, perhaps as a consequence, often grows in large, dense populations. It is reported as possibly extirpated from Louisiana, where it was documented from Washington Parish. Asclepias amplexicaulis Michaux, an illegitimate synonym, created confusion between this species and A. amplexicaulis Smith, a similarly glaucous, cordate-leaved species. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 14. | FNA vol. 14. |
Parent taxa | Apocynaceae > Asclepias | Apocynaceae > Asclepias |
Sibling taxa | ||
Synonyms | Acerates ivesii, A. viridiflora var. lanceolata, A. viridiflora var. linearis | |
Name authority | Rafinesque: Med. Repos., hexade 2, 5: 360. (1808) | Walter: Fl. Carol., 105. (1788) |
Web links |
|