Asclepias stenophylla |
Asclepias incarnata |
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narrow-leaf milkweed, slimleaf milkweed |
asclépiade incarnate, rose milkweed, swamp milkweed, swamp silkweed, white Indian hemp |
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Habit | Herbs. | Herbs. | ||||
Stems | 1 or 2 (rarely more), erect to spreading, rarely branched, 15–85 cm, puberulent with curved trichomes, not glaucous, rhizomes absent. |
1–few, erect, unbranched to inflorescence, 30–150 cm, puberulent in a line with curved trichomes or densely pilose to glabrate, not glaucous, rhizomes absent. |
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Leaves | alternate, subopposite, or opposite, sessile or petiolate, with 1 stipular colleter on each side of petiole; petiole 0–1 mm, spreading to ascending, glabrate; blade linear, conduplicate, 5–16 × 0.1–0.5 cm, chartaceous, base cuneate, margins entire, apex acute, venation faintly brochidodromous to obscure, surfaces sparsely puberulent with curved trichomes, especially on midvein, to glabrate, margins ciliate, laminar colleters absent. |
opposite, petiolate, with 1 or 2 stipular colleters on each side of petiole on a ciliate interpetiolar ridge; petiole 1–15 mm, pilosulous to pilose; blade lanceolate to linear-lanceolate or ovate, 5–15 × 0.5–4.5 cm, membranous, base obtuse to rounded or subcordate, margins entire, apex acute to acuminate or attenuate, venation eucamptodromous, surfaces sparsely puberulent with curved trichomes or pilose to glabrate, margins ciliate, 2–6 laminar colleters. |
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Inflorescences | extra-axillary, sessile or pedunculate, 9–28-flowered; peduncle 0–1.3 cm, sometimes branched at apex, puberulent with curved trichomes, with 1 caducous bract at the base of each pedicel. |
extra-axillary at upper nodes, branched, pedunculate, 10–31-flowered; peduncle 1.5–7 cm, puberulent with curved trichomes to pilosulous, sometimes only on 1 side, to pilose, with 1 caducous bract at the base of each pedicel. |
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Pedicels | 5–12 mm, puberulent with curved trichomes to pilosulous. |
10–15 mm, pilosulous to puberulent with curved trichomes, sometimes only on 1 side, to pilose. |
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Flowers | erect to pendent; calyx lobes lanceolate, 1.5–2.5 mm, apex acute, puberulent with curved trichomes to pilosulous; corolla pale green to greenish cream, lobes reflexed with spreading tips, elliptic, 3–5 mm, apex acute, minutely puberulent with curved trichomes at apex abaxially, glabrous adaxially; gynostegial column 0–0.5 mm, fused anthers green, truncately obconic, 1.5–2 mm, wings narrowly crescent-shaped, wide open at base, apical appendages deltoid; corona segments cream, often green-tinged, sessile, chute-shaped, margins incurved, appressed to anthers, 3–3.5 mm, equaling style apex, base saccate, auriculate, apex truncate, glabrous, internal appendage a short crest, the segment appearing 3-toothed, glabrous; style apex shallowly depressed, green. |
erect; calyx lobes lanceolate, 2–2.5 mm, apex acute, pilosulous to puberulent with curved trichomes; corolla pink to white, lobes reflexed with spreading tips, elliptic, (4.5–)5–6 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially; gynostegial column 1.2–1.5 mm; fused anthers green to brown, columnar, 1.5–2 mm, wings narrowly right-triangular, slightly open at base, apical appendages deltoid; corona segments pink to white, often paler than corolla, stipitate, tubular, dorsally rounded to slightly flattened, 2–2.5 mm, ± equaling style apex, apex obtuse, glabrous, internal appendage acicular, exserted, arching over style apex, glabrous; style apex shallowly depressed, green, white, or pink. |
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Seeds | ovate, 6–7 × 4–5 mm, margin winged, faces minutely rugulose; coma 2.5–3 cm. |
ovate, 8–9 × 5–6 mm, margin broadly winged, faces smooth; coma 1.5–2 cm. |
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Follicles | erect on straight pedicels, fusiform, 9–13 × 1–1.2 cm, apex long-acuminate, smooth, pilosulous. |
erect on straight pedicels, fusiform, 6–9 × 0.8–1.2 cm, apex long-acuminate, smooth to indistinctly ribbed, sparsely puberulent with curved trichomes to pilose or pilosulous. |
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Asclepias stenophylla |
Asclepias incarnata |
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Phenology | Flowering May–Aug; fruiting (Jun–)Aug–Oct. | |||||
Habitat | Hills, ridges, bluffs, slopes, flats, glades, sandhills, streamsides, limestone, dolomite, rhyolite, sandy and clay soils, prairies, pastures, thickets, forest openings, pine savannas. | |||||
Elevation | 70–1900 m. (200–6200 ft.) | |||||
Distribution |
AR; CO; IA; IL; KS; LA; MN; MO; MT; NE; OK; SD; TX; WY
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North America; n Mexico
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Discussion | Although Asclepias stenophylla is a distinctive species, it is difficult to distinguish from A. engelmanniana in the absence of flowers or fruits, where their ranges overlap in the Great Plains. The drooping leaves of A. engelmanniana can reliably distinguish that species from A. stenophylla. Asclepias stenophylla is also often mistaken for A. verticillata, but the nearly appendageless corona segments and alternate or opposite (versus whorled) leaves readily separate A. stenophylla from that species. Because of its slender habit, linear leaves, and small clusters of greenish cream flowers held close to the stem, it can be overlooked in its grassland habitats. Asclepias stenophylla is widespread and common in its core habitat of Ozark glades and dry sites in tallgrass in Missouri, and in mixed-grass prairies from South Dakota to Texas. It is quite rare at the margins of its range in Arkansas (Baxter County), Illinois (Adams, Calhoun, and Pike counties), Iowa (Guthrie, Plymouth, and Sioux counties), Louisiana (Winn Parish), Minnesota (Houston County), Montana (Carter County), and Wyoming (Crook and Weston counties). In Colorado, it exhibits an interesting disjunction between Yuma County in the east and the Front Range of the Rocky Mountains, where it is sporadic, but impacted by development and considered to be of conservation concern. A report from North Dakota has not been confirmed. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Subspecies 2 (2 in the flora). Asclepias incarnata can be grown in a great variety of soil types and is surprisingly drought tolerant considering its natural predilection for hydric and mesic soils. As an easily grown, attractive, versatile species, it is one of the best options for gardening with milkweeds. It consists of two morphologically and geographically distinct, but intergrading subspecies. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 14. | FNA vol. 14. | ||||
Parent taxa | Apocynaceae > Asclepias | Apocynaceae > Asclepias | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Polyotus angustifolius, Acerates angustifolia | |||||
Name authority | A. Gray: Proc. Amer. Acad. Arts 12: 72. (1876) | Linnaeus: Sp. Pl. 1: 215. (1753) | ||||
Web links |