Asclepias stenophylla
Asclepias lanceolata
narrow-leaf milkweed, slimleaf milkweed
few-flower milkweed, smooth-orange milkweed
1 or 2 (rarely more), erect to spreading, rarely branched, 15–85 cm, puberulent with curved trichomes, not glaucous, rhizomes absent.
1, erect, unbranched, 60–125 cm, glabrous, not glaucous, rhizomes absent.
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 or petiolate, with 1 stipular colleter on each side of petiole on a ciliate interpetiolar ridge;
petiole 0–1 mm, ciliate;
blade linear to linear-lanceolate, somewhat conduplicate, 7–25 × 0.2–1.7 cm, chartaceous, base cuneate, margins entire, apex attenuate, mucronate, venation faintly brochidodromous to obscure, surfaces glabrous, margins inconspicuously ciliate, 8–12 laminar colleters, usually obscured by conduplicate petiole.
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 often extra-axillary at an upper node, usually branched, pedunculate, 4–16-flowered;
peduncle 1–7.5 cm, puberulent on 1 side with curved trichomes, with 1 caducous bract at the base of each pedicel.
5–12 mm, puberulent with curved trichomes to pilosulous.
13–19 mm, puberulent on 1 side with curved trichomes.
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 narrowly lanceolate, 2–3 mm, apex acute, puberulent with curved trichomes to glabrate;
corolla red, lobes reflexed, usually with spreading tips, elliptic, 9–10 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially;
gynostegial column 1.5–2 mm;
fused anthers green, tinged yellow to red, truncately obconic, 2.5 mm, wings narrowly right-triangular, slightly open at base, apical appendages deltoid;
corona segments yellow to reddish orange, stipitate, broadly tubular, dorsally flattened, 5–6 mm, exceeding style apex, apex obtuse, flared, glabrous, internal appendage subulate, exserted, sharply inflexed over style apex, glabrous;
style apex shallowly depressed, red.
ovate, 6–7 × 4–5 mm, margin winged, faces minutely rugulose;
coma 2.5–3 cm.
broadly oval, 8–10 × 6–8 mm, margin winged, faces smooth;
coma 3–3.5 cm.
erect on straight pedicels, fusiform, 9–13 × 1–1.2 cm, apex long-acuminate, smooth, pilosulous.
erect on upcurved pedicels, narrowly fusiform, 5.5–10 × 0.8–1 cm, apex attenuate to long-acuminate, smooth, sparsely pilosulous or puberulent with curved trichomes to glabrate.
Asclepias stenophylla
Asclepias lanceolata
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 lanceolata is a characteristic wetland milkweed of the Atlantic and Gulf coastal plains, where it occurs sometimes with its similar relative, A. rubra. It is distinguished from A. rubra by flower color (shades of orange, yellow, and red versus pink, lavender, and reddish purple), corona segment apex (obtuse versus acute), and leaf shape (linear to linear-lanceolate versus narrowly lanceolate to ovate). These species are known to hybridize locally, particularly in North Carolina, and putative hybrids can be recognized by intermediate floral and vegetative traits. The pattern of yellow-orange coronas paired with red corollas is similar to that of the introduced A. curassavica, and these species are sometimes confused. Asclepias curassavica differs by usually pure yellow (versus orangish) coronas, more flowers per umbel, much shorter peduncles, and wider, shorter leaf blades. Asclepias lanceolata sometimes is confused also with orange-flowered A. tuberosa, although that species only rarely has bicolored flowers, and the two are quite distinct in habitat, growth form, and vestiture. Through habitat loss, A. lanceolata has become quite rare in some areas, particularly the northeastern United States. It is considered to be of conservation concern in Delaware (Sussex County), Maryland (Dorchester County), and New Jersey. It has been reported, but not documented, from Tennessee, and its occurrence there seems unlikely. The report may be based on confusion with the name of the formerly recognized (and unrelated) A. viridiflora var. lanceolata.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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