Asclepias cordifolia |
Asclepias texana |
|
---|---|---|
heart-leaf milkweed, purple milkweed |
Texas milkweed |
|
Habit | Herbs. | Subshrubs or herbs. |
Stems | 1–20, ascending to spreading, unbranched, 25–100 cm, glabrous, glaucous, rhizomes absent. |
1–numerous, erect, sparsely to moderately branched in upper half, 25–90 cm, puberulent with curved trichomes in a line, 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 or 2 stipular colleters on each side of petiole on a ciliate interpetiolar ridge; petiole 5–20 mm, puberulent with curved trichomes; blade ovate to lanceolate or elliptic, 2–7 × 0.5–3 cm, chartaceous, base cuneate to obtuse, margins entire, apex acute to acuminate, venation eucamptodromous, surfaces puberulent with curved trichomes on veins abaxially, sparsely puberulent with curved trichomes on veins to glabrate adaxially, margins ciliate, laminar colleters absent. |
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. |
extra-axillary at upper nodes, some appearing terminal, pedunculate, 14–31-flowered; peduncle 0.9–3 cm, puberulent with curved trichomes in a line, with 1 caducous bract at the base of each pedicel. |
Pedicels | 16–37 mm, sparsely pilose. |
7–14 mm, puberulent with curved trichomes in a line. |
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; calyx lobes narrowly lanceolate, 1.5–2 mm, apex acute, puberulent with curved trichomes; corolla white, sometimes tinged green, lobes reflexed with spreading tips, elliptic, 3.5–5 mm, apex acute to obtuse, glabrous abaxially, minutely papillose at base adaxially; gynostegial column 1–1.5 mm; fused anthers brown, columnar, 1.5–2 mm, wings narrowly right-triangular, closed, apical appendages deltoid; corona segments white, sometimes tinged pink, stipitate, cupulate, dorsally rounded, 2–3 mm, equaling to slightly exceeding style apex, apex obtuse, glabrous, internal appendage acicular, exserted, arching over style apex, glabrous; style apex shallowly depressed, white. |
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 smooth or sparsely papillose; coma 2–3 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 straight pedicels, narrowly fusiform, 9–13 × 0.5–1 cm, apex long-acuminate to attenuate, smooth, glabrous. |
2n | = 22. |
|
Asclepias cordifolia |
Asclepias texana |
|
Phenology | Flowering Mar–Jul(–Aug); fruiting Jun–Sep. | Flowering May–Sep; fruiting (Jul–)Aug–Oct. |
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. | Canyons, arroyos, slopes, cliff bases, bluffs, streamsides, limestone, igneous rocks, rocky and clay soils, riparian, oak-juniper, and oak woods, pine-oak forest. |
Elevation | 50–2200(–2800) m. (200–7200(–9200) ft.) | 300–2000 m. (1000–6600 ft.) |
Distribution |
CA; NV; OR
|
TX; Mexico (Coahuila, Nuevo León) |
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.) |
In the flora area, Asclepias texana has a disjunct distribution on the Edwards Plateau and in the mountains of the Big Bend region. Although commonly occurring in canyons and riparian areas, A. texana is quite drought tolerant in cultivation. The tidy, bushy habit, long flowering stems topped by bright white spherical umbels, and rapid growth from seed make this a suitable candidate for horticultural use. It is known to be hardy to at least USDA Zone 7. (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 | Acerates cordifolia, Gomphocarpus cordifolius | A. perennis var. parvula |
Name authority | (Bentham) Jepson: Fl. W. Calif., 384. (1901) | A. Heller: Contr. Herb. Franklin Marshall Coll. 1: 77, plate 4. (1895) |
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