Asclepias obovata |
Asclepias verticillata |
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pineland milkweed |
asclépiade verticillée, eastern whorled milkweed, horsetail milkweed, whorled milkweed |
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Habit | Herbs. | Herbs. |
Stems | 1 (rarely more), erect to spreading, unbranched, 40–70(–200) cm, densely hirtellous to velutinous, not glaucous, rhizomes absent. |
1 (rarely 2 or 3), erect, sparingly branched, arrested vegetative branches absent, 35–90 cm, sparsely puberulent with curved trichomes in lines, not glaucous, rhizomatous. |
Leaves | opposite, petiolate, with 1 or 2 stipular colleters on each side of petiole; petiole 1–4 mm, densely hirtellous to velutinous; blade oblong or elliptic to obovate or ovate, 4–9 × 1–3.5 cm, subcoriaceous, base rounded or truncate to cordate, margins sometimes crisped, apex acute to truncate, sometimes emarginate, often mucronate, venation brochidodromous, surfaces densely hirtellous to velutinous abaxially, hirtellous adaxially, margins ciliate, 8–12 laminar colleters. |
3–6-whorled, sessile, with 1 stipular colleter on each side of leaf base on a ciliate interpetiolar ridge; blade linear, 1.5–7 × 0.1–0.2 cm, chartaceous, base cuneate, margins entire, apex acute, mucronate, venation obscure, surfaces glabrous abaxially, puberulent with curved trichomes adaxially, especially on midvein, to glabrate, margins ciliate, laminar colleters absent. |
Inflorescences | extra-axillary, sometimes also appearing terminal, sessile or pedunculate, 7–31-flowered; peduncle 0–0.5 cm, densely hirtellous to velutinous, with 1 caducous bract at the base of each pedicel. |
extra-axillary at upper nodes, pedunculate, 7–28-flowered; peduncle 0.8–4 cm, puberulent with curved trichomes on 1 side, with 1 caducous bract at the base of each pedicel. |
Pedicels | 10–12 mm, densely hirtellous to velutinous. |
6–10 mm, puberulent with curved trichomes. |
Flowers | erect to pendent; calyx lobes elliptic, 5–6 mm, apex acute, densely hirtellous; corolla green, sometimes tinged reddish or bronze, lobes reflexed, sometimes with spreading tips, elliptic, 7–9 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially; gynostegial column 1–1.5 mm; fused anthers green, obconic, 2.5–4 mm, wings right-triangular, open at base, apical appendages broadly ovate; corona segments bronze to yellow, often tinged red, sometimes apically cream or pale, stipitate, tubular, somewhat flattened laterally, flared at base, 5–8 mm, greatly exceeding style apex, apex rounded, flared, glabrous, internal appendage falcate, exserted, sharply incurved over style apex, glabrous; style apex shallowly depressed, green. |
erect to spreading; calyx lobes lanceolate, 1.5–2 mm, apex acute, puberulent with curved trichomes to glabrate; corolla pale green to cream or ochroleucous, sometimes tan-tinged, lobes reflexed with spreading tips, elliptic, 3–4 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially; gynostegial column 1–1.2 mm; fused anthers green, columnar, 1.2–1.5 mm, wings narrowly right-triangular, closed, apical appendages deltoid; corona segments cream, stipitate, cupulate, dorsally flattened, 1.5–2 mm, exceeded by style apex, apex obtuse, margin shallowly lobed (sometimes obscure) to sharply toothed proximally, glabrous, internal appendage acicular, exserted, arching over style apex, glabrous; style apex shallowly depressed, green to greenish cream. |
Seeds | broadly ovate, 8–9 × 6–7 mm, margin winged, faces smooth; coma 2–5 cm. |
ovate, 6–7 × 4–5 mm, margin winged, faces smooth; coma 2.5–3.5 cm. |
Follicles | erect on upcurved pedicels, narrowly to broadly fusiform, 7.5–12.5 × 1.5–2.5 cm, apex acuminate, smooth, densely hirtellous to velutinous. |
erect on straight pedicels, narrowly fusiform, 6–11 × 0.4–0.8 cm, apex acuminate to attenuate, smooth, glabrous. |
2n | = 22. |
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Asclepias obovata |
Asclepias verticillata |
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Phenology | Flowering May–Sep; fruiting Jul–Oct. | Flowering Feb–Oct; fruiting Mar–Nov(–Dec). |
Habitat | Hills, slopes, flats, ridges, sandhills, ditches, seeps, bogs, sandstone, sandy, rocky, silty, and clay soils, pine flatwoods, pine savannas, pine, pine-oak, and bottomland hardwood forests, prairies, often following fires. | Ridges, slopes, flats, glades, bluffs, dunes, sandhills, streamsides, wet meadows and depressions, lake shores, sandstone, limestone, granite, serpentine, dolomite, shale, sandy, clay, and rocky soils, prairies, pine flatwoods and barrens, pine and oak scrubs, oak and oak-hickory woodlands, pine, pine-oak and pine-mixed-hardwood forests, forest edges. |
Elevation | 0–200 m. (0–700 ft.) | 0–1000 m. (0–3300 ft.) |
Distribution |
AL; AR; FL; GA; LA; MS; OK; SC; TX
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AL; AR; CT; DC; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; MI; MN; MO; MS; MT; NC; ND; NE; NJ; NY; OH; OK; PA; RI; SC; SD; TN; TX; VA; VT; WI; WV; MB; ON; SK
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Discussion | Asclepias obovata is a common milkweed of seasonally wet, sandy soils in pine woodlands of the Gulf Coastal Plain and (rarely) the southern Atlantic Coastal Plain. It is rare and considered to be of conservation concern in Arkansas. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Asclepias verticillata is parapatric with the closely related and morphologically similar A. linearis, A. pumila, and A. subverticillata. It can be difficult to distinguish from these relatives where their ranges overlap. Similarities with A. linearis and A. subverticillata are discussed under those species; no definitive hybrids between A. verticillata and these species have been documented. The characteristic marginal corona segment tooth is often reduced to a shallow lobe in western populations of A. verticillata, which complicates distinguishing this species from A. subverticillata, and which suggests past introgression. A widely disjunct collection of A. verticillata was made in Arizona, well within the range of A. subverticillata, for Plants of the Hopis (Millspaugh 176 [F]); persistence of the species in Arizona has not been documented by additional collections. Hybrids with A. pumila are usually readily detected because the parental species are distinct in leaf arrangement and internode length (whorled and distant nodes in A. verticillata versus alternate and congested in A. pumila). These hybrids often have mixed phyllotaxy and have been documented in Kansas, Montana, South Dakota, and Texas. Asclepias verticillata is strongly rhizomatous and forms dense colonies on roadsides and in prairies; in forests, however, genets are small and solitary stems are common. Like several other milkweed species, it is rare and declining at the northeastern terminus of its range (in Delaware, Massachusetts, New Jersey, Pennsylvania, Rhode Island, and Vermont). It is also considered rare in Saskatchewan, where it has been documented by few specimens. Reports from Wyoming (Crook County) all seem to pertain to A. pumila (B. Heidel, pers. comm.). (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 | ||
Name authority | Elliott: Sketch Bot. S. Carolina 1: 321. (1817) | Linnaeus: Sp. Pl. 1: 217. (1753) |
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