Asclepias stenophylla
Asclepias eriocarpa
narrow-leaf milkweed, slimleaf milkweed
Indian milkweed, kotolo, woollypod milkweed, wooly-pod or kotolo or Indian milkweed
1 or 2 (rarely more), erect to spreading, rarely branched, 15–85 cm, puberulent with curved trichomes, not glaucous, rhizomes absent.
1–10, erect to spreading, rarely branched, 30–100 cm, tomentose to puberulent with curved trichomes or glabrate, not glaucous, rhizomatous.
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, or alternate or whorled at upper nodes, petiolate, with 0–2 stipular colleters on each side of petiole (sometimes additionally in the axil);
petiole 4–15 mm, tomentose;
blade oblong or oval to lanceolate or ovate, often conduplicate, 8–20 × 2–8 cm, chartaceous, base obtuse or truncate to cordate, margins entire or often undulate, apex acuminate to obtuse, mucronate, venation brochidodromous, surfaces tomentose to densely puberulent with curved trichomes, margins ciliate, 6–8 laminar colleters.
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, sometimes branched, and extra-axillary at upper nodes, pedunculate, 12–57-flowered;
peduncle 1–10 cm, densely tomentose, with 1 caducous bract at the base of each pedicel.
5–12 mm, puberulent with curved trichomes to pilosulous.
15–50 mm, densely tomentose.
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 to spreading;
calyx lobes lanceolate, 3–4 mm, apex acute, densely tomentose;
corolla greenish cream, ochroleucous, or pinkish cream, deep pink or tan abaxially, lobes reflexed, tips usually spreading, oval, 7–9 mm, apex acute, tomentose abaxially towards tips, glabrous adaxially;
gynostegial column 1–1.5 mm;
fused anthers dark brown, cylindric, 2.5–3 mm, wings right-triangular, closed, apical appendages ovate;
corona segments cream to dark pink, stipitate, conduplicate, dorsally rounded, 2.5–3 mm, exceeded by style apex, apex truncate, oblique, papillose, internal appendage falcate, exserted, sharply inflexed towards style apex, papillose;
style apex shallowly depressed, cream.
ovate, 6–7 × 4–5 mm, margin winged, faces minutely rugulose;
coma 2.5–3 cm.
ovate, 7–9 × 4–6 mm, margin narrowly winged, faces faintly rugulose;
coma 2.5–3 cm.
erect on straight pedicels, fusiform, 9–13 × 1–1.2 cm, apex long-acuminate, smooth, pilosulous.
erect on upcurved pedicels, lance-ovoid, 5–10 × 1.5–3 cm, apex apiculate, smooth, densely tomentose.
Asclepias stenophylla
Asclepias eriocarpa
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 eriocarpa is found almost throughout the California Floristic Province in relatively dry, open sites in a variety of vegetation types. It is the only milkweed in the flora area that regularly produces alternate, opposite, and whorled leaves on a single stem. Its distribution overlaps that of several other broad-leaved, densely vestitured Asclepias species: A. erosa in desert scrub and dry grasslands, A. californica and A. vestita in chaparral and woodlands, and A. speciosa in woodlands. Comparison to A. erosa is presented under that species. Asclepias eriocarpa is easily distinguished from A. californica by the distinctive red-violet, rounded corona segments that lack appendages in the latter species. Asclepias eriocarpa has corona segments with truncate apices and corolla lobes that are tomentose abaxially only at the apex, in contrast to the obtuse corona segments and uniformly pubescent corolla lobes of A. vestita. Asclepias speciosa has distinctive corona segments with long, tapering apices that are much larger than and are easily distinguished from those of A. eriocarpa. It is possible that A. eriocarpa and A. speciosa occasionally hybridize—R. E. Woodson Jr. speculated (via annotation of the holotype, E. Gifford s.n. [CAS]) that A. giffordii Eastwood represented such a hybrid. That interpretation is accepted here. Asclepias eriocarpa is reported to be a resource for fiber and medicine by Native Americans.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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