Asclepias cordifolia |
Asclepias hypoleuca |
|
---|---|---|
heart-leaf milkweed, purple milkweed |
mahogany milkweed, talayote |
|
Habit | Herbs. | Herbs. |
Stems | 1–20, ascending to spreading, unbranched, 25–100 cm, glabrous, glaucous, rhizomes absent. |
1 (rarely 2 or 3), erect, unbranched, 25–100 cm, puberulent with curved trichomes to pilosulous, not glaucous, rhizomes absent. |
Leaves | opposite, sessile, stipular colleters absent; blade ovate to lanceolate, 3.5–11 × 1.8–8 cm, chartaceous, base cordate, clasping, margins entire, apex acute, mucronate, venation brochidodromous to eucamptodromous, surfaces glabrous, glaucous, margins minutely ciliate, laminar colleters absent. |
opposite, petiolate, with 1 stipular colleter on each side of petiole; petiole 2–6 mm, puberulent with curved trichomes to pilosulous; blade ovate or lanceolate to oblong, elliptic, or oval, 5.5–11.5 × 1–5 cm, chartaceous, base cuneate or obtuse to truncate, margins entire, apex obtuse to rounded, mucronate, venation eucamptodromous, surfaces tomentose abaxially, pilosulous or tomentulose to glabrate adaxially, margins ciliate, 8–12 laminar colleters. |
Inflorescences | terminal, branched, sometimes also extra-axillary at upper nodes, pedunculate, 5–20-flowered; peduncle 0.3–6.5 cm, apically sparsely pilose to glabrate, with few bracts. |
terminal and extra-axillary, pedunculate, 12–35-flowered; peduncle 3.5–10.5 cm, puberulent with curved trichomes to tomentulose, with 1 caducous bract at the base of each pedicel. |
Pedicels | 16–37 mm, sparsely pilose. |
15–21 mm, densely puberulent with curved trichomes or pilosulous to tomentulose. |
Flowers | erect to pendent; calyx lobes elliptic to lanceolate, 3–5 mm, apex acute, pilose; corolla red-violet, lobes reflexed with spreading tips, oval, 6–7 mm, apex acute, glabrous; gynostegial column 1–1.5 mm; fused anthers brown, cylindric, 1.5–2 mm, wings right-triangular, open at tip, apical appendages deltoid; corona segments white, tinged pink to red-violet at base, sessile, tubular, 2–3 mm, exceeded by style apex, base saccate, apex truncate, oblique, glabrous, internal appendage absent; style apex shallowly depressed, pink to red-violet. |
erect to pendent; calyx lobes lanceolate, 3–4 mm, apex acute, pilose; corolla green, sometimes red-tinged abaxially, deep maroon to greenish red or green adaxially, lobes reflexed, tips usually spreading, oblong to elliptic, 8–10 mm, apex acute, pilosulous abaxially, glabrous adaxially; gynostegial column 1–1.5 mm; fused anthers brown, broadly cylindric, 2–2.5 mm, wings right-triangular, open at tip, apical appendages ovate, erose; corona segments deep maroon to greenish red or yellowish green, subsessile, conduplicate, 7–9 mm, greatly exceeding style apex, apex truncate, spreading and long-tapering with a proximal tooth on each side, glabrous, internal appendage absent or a low crest, glabrous; style apex shallowly depressed, green. |
Seeds | ovate, 8–9 × 5–7 mm, margin not winged, faces reticulate-rugulose; coma 3–3.5 cm. |
ovate, 6–7 × 4–5 mm, margin winged, faces minutely rugulose; coma 3–3.5 cm. |
Follicles | erect on upcurved pedicels, lance-ovoid, 7.5–10.5 × 1.5–1.8 cm, apex long-acuminate, smooth, glabrous, glaucous. |
erect on upcurved pedicels, fusiform, 9–11.5 × 1.2–1.4 cm, apex long-attenuate, smooth, sometimes faintly striate, pilosulous to tomentulose. |
2n | = 22. |
|
Asclepias cordifolia |
Asclepias hypoleuca |
|
Phenology | Flowering Mar–Jul(–Aug); fruiting Jun–Sep. | Flowering Jun–Sep; fruiting Aug–Sep. |
Habitat | Hillsides, canyons, ridge tops, streamsides, seeps, basalt, serpentine, gabbro, granite, shale, limestone, talus slopes, gravel, alluvium, oak woodlands, mixed evergreen, douglas-fir, pine, pine-oak, and riparian forests, chaparral, timberline meadows, grasslands. | Slopes, flats, lake shores, streamsides, granite, gneiss, andesite, rocky soils, pine, pine-oak, oak, and mixed-conifer forests. |
Elevation | 50–2200(–2800) m. [160–7200(–9200) ft.] | 1900–2800 m. [6200–9200 ft.] |
Distribution |
CA; NV; OR
|
AZ; NM; Mexico (Chihuahua, Sonora)
|
Discussion | Fresh leaves and stems of Asclepias cordifolia are often slightly or strongly colored bluish, grayish, or purplish. This is one of the few American species of Asclepias with cavitate corona segments that lack adaxial appendages. Such species were segregated along with diverse African species in Gomphocarpus R. Brown, a polyphyletic segregate (M. Fishbein et al. 2011; D. Chuba et al. 2017). Asclepias cordifolia is a distinctive species unlike any other within its range. It is phylogenetically and geographically isolated, although not highly derived morphologically. In Nevada, A. cordifolia is restricted to the Sierra Nevada, in Carson City, Douglas, and Washoe counties. Its range extends to northern California and southwestern Oregon. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Asclepias hypoleuca grows at higher elevations in the sky-island mountain ranges than any other milkweed. It has been documented from the Chiricahua, Huachuca, Rincon, Santa Catalina, Santa Rita, and White mountain ranges in Arizona (Cochise, Pima, and Santa Cruz counties) and the Mogollon Mountains and Black Range in New Mexico (Catron and Grant counties). Because of its limited, high-elevation distribution, and the threats of changing climate, its conservation status in the flora area merits assessment. The bicolored leaves exhibit coloration similar to co-occurring silverleaf oak (Quercus hypoleucoides). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 14. | FNA vol. 14. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Acerates cordifolia, Gomphocarpus cordifolius | Gomphocarpus hypoleucus |
Name authority | (Bentham) Jepson: Fl. W. Calif., 384. (1901) | (A. Gray) Woodson: Ann. Missouri Bot. Gard. 28: 206. (1941) |
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