Asclepias stenophylla |
Asclepias pedicellata |
|
---|---|---|
narrow-leaf milkweed, slimleaf milkweed |
savanna milkweed, savannah milkweed |
|
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, erect, unbranched, 10–45 cm, puberulent with curved trichomes, not glaucous, rhizomes absent. |
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, sessile, with 1 stipular colleter on each side of leaf base; blade linear to narrowly elliptic or narrowly lanceolate, 1.5–6 × 0.1–0.8 cm, chartaceous, base cuneate, margins entire, apex acute, mucronate, venation obscure to eucamptodromous, surfaces puberulent with curved trichomes or scabridulous to glabrate, margins ciliate, 2 laminar colleters. |
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. |
terminal and extra-axillary at upper nodes, pedunculate, 2–7-flowered; peduncle 0.15–1 cm, densely puberulent with curved trichomes, with 1 caducous bract at the base of each pedicel. |
Pedicels | 5–12 mm, puberulent with curved trichomes to pilosulous. |
5–13 mm, minutely puberulent with curved trichomes. |
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 elliptic, 2–3 mm, apex acute, sparsely puberulent with curved trichomes to glabrate; corolla yellowish green to green, lobes erect, mostly concealing corona, narrowly elliptic, 7–10 mm, apex acute, glabrous; gynostegial column 4–6 mm; fused anthers green, broadly conic, 1–1.5 mm, wings right-triangular with decurrent base, closed, apical appendages ovate; corona segments yellowish green to green, sometimes dark green at apex, sessile, conduplicate, 1.5–2.5 mm, greatly exceeded by style apex, apex incurved, rounded, glabrous, internal appendage absent; style apex flat, green. |
Seeds | ovate, 6–7 × 4–5 mm, margin winged, faces minutely rugulose; coma 2.5–3 cm. |
ovate, 5–6 × 3–4 mm, margin winged, faces sparsely and minutely rugulose; coma 2–2.5 cm. |
Follicles | erect on straight pedicels, fusiform, 9–13 × 1–1.2 cm, apex long-acuminate, smooth, pilosulous. |
erect on straight pedicels, fusiform, 8–14 × 0.3–0.5 cm, apex long-attenuate, smooth, densely puberulent with curved trichomes. |
Asclepias stenophylla |
Asclepias pedicellata |
|
Phenology | Flowering May–Aug; fruiting (Jun–)Aug–Oct. | Flowering Mar–Nov(–Dec); fruiting May–Oct. |
Habitat | Hills, ridges, bluffs, slopes, flats, glades, sandhills, streamsides, limestone, dolomite, rhyolite, sandy and clay soils, prairies, pastures, thickets, forest openings, pine savannas. | Flats, streamsides, sandhills, sandy soils, pine flatwoods, savannas, pine-palmetto and oak-palmetto scrubs, often following fires. |
Elevation | 70–1900 m. (200–6200 ft.) | 0–100 m. (0–300 ft.) |
Distribution |
AR; CO; IA; IL; KS; LA; MN; MO; MT; NE; OK; SD; TX; WY
|
FL; GA; NC; SC
|
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.) |
Asclepias pedicellata is found in drier habitats than some co-distributed milkweeds, such as A. connivens and A. viridula. It sometimes occurs in the same sites as A. cinerea, A. curtissii, and A. feayi. The erect petals and elongate gynostegial column are unique among Asclepias species in the flora area. The green flowers with hidden coronas and low stature of the plants can make them frustratingly cryptic in their grass-dominated habitats. Asclepias pedicellata is common only in Florida and North Carolina and is considered rare and of conservation concern in the intervening region in Georgia and South Carolina. (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 | Polyotus angustifolius, Acerates angustifolia | Podostigma pedicellatum |
Name authority | A. Gray: Proc. Amer. Acad. Arts 12: 72. (1876) | Walter: Fl. Carol., 106. (1788) |
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