Flora of North America species comparison

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Asclepias cordifolia

Asclepias emoryi
Asclepias cordifolia

heart-leaf milkweed, purple milkweed

Emory's milkweed
Habit Herbs. Herbs.
Stems

1–20, ascending to spreading, unbranched, 25–100 cm, glabrous, glaucous, rhizomes absent.

1–4, erect to spreading, unbranched or rarely branched near base, 6–30 cm, puberulent with curved trichomes to hirtellous, 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.

persistent or gradually caducous from base, opposite, sessile or petiolate, with 1 stipular colleter on each side of petiole;

petiole 0–17 mm, puberulent with curved trichomes to hirtellous;

blade elliptic to lanceolate or lance-ovate, 3–7.5 × 0.4–2.5 cm, chartaceous, base cuneate, margins often crisped, apex acute, venation eucamptodromous, surfaces hirtellous, usually conduplicate, 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, sessile or pedunculate, 4–8-flowered;

peduncle 0–2 cm, hirtellous, with 1 caducous bract at the base of each pedicel.
Pedicels

16–37 mm, sparsely pilose.

7–10 mm, hirtellous.
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 linear-lanceolate to narrowly elliptic, 3–4 mm, apex acute, hirtellous;

corolla green, sometimes tinged red or brown, faintly striate, lobes reflexed, elliptic, 5–7 mm, apex acute, hirtellous throughout or glabrate at tips abaxially, glabrous adaxially;

gynostegial column 0.5–1 mm;

fused anthers green, obconic, 1–1.5 mm, wings trapezoidal, closed, apical appendages ovate;

corona segments proximally green, distally white or cream, sessile, tubular, 3.5–5.5 mm, greatly exceeding style apex, apex flared, deeply emarginate, minutely papillose, internal appendage lingulate, sharply incurved, at the same level as and closing the segment apex, minutely papillose.
Seeds

ovate, 8–9 × 5–7 mm, margin not winged, faces reticulate-rugulose;

coma 3–3.5 cm.

oval, 7 × 5–6 mm, margin winged, faces smooth;

coma 2.5–3.5 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, lance-ovoid, 5–9 × 1.2–2 cm, apex attenuate to acuminate, smooth, puberulent with curved trichomes to hirtellous, sometimes faintly striate.
2n

= 22.

Asclepias cordifolia

Asclepias emoryi
Phenology Flowering Mar–Jul(–Aug); fruiting Jun–Sep. Flowering Mar–Aug(–Oct); fruiting Jul–Nov.
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. Plains, hills, slopes, limestone, caliche, sandy, clay, rocky, calcareous, and gravelly soils, prairies, mesquite grasslands, thorn scrub.
Elevation 50–2200(–2800) m. [160–7200(–9200) ft.] 0–800 m. [0–2600 ft.]
Distribution
from FNA
CA; NV; OR
[WildflowerSearch map]
[BONAP county map]
from FNA
TX; Mexico (Coahuila, Nuevo León, San Luis Potosí, Tamaulipas)
[BONAP county map]
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 emoryi is distributed entirely within the range of its close relative, A. oenotheroides. Distinguishing them is discussed under the latter species. A few putative hybrid specimens have been collected. These can be distinguished from A. emoryi by slightly longer corona segments (usually shorter than in A. oenotheroides) with sinuate apices, slightly longer corolla lobes, and slightly broader leaves. Although not accorded conservation concern, A. emoryi is very rarely encountered (across its entire range) and merits study for evaluation of needed protections. Reports of A. emoryi from New Mexico are based upon misidentifications. It is restricted in the flora area almost entirely to southern Texas, but there are a few scattered occurrences to the northwest.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 14. Treatment author: Mark Fishbein. FNA vol. 14. Treatment author: Mark Fishbein.
Parent taxa Apocynaceae > Asclepias Apocynaceae > Asclepias
Sibling taxa
A. albicans, A. amplexicaulis, A. angustifolia, A. arenaria, A. asperula, A. brachystephana, A. californica, A. cinerea, A. connivens, A. cryptoceras, A. curassavica, A. curtissii, A. cutleri, A. eastwoodiana, A. elata, A. emoryi, A. engelmanniana, A. eriocarpa, A. erosa, A. exaltata, A. fascicularis, A. feayi, A. hallii, A. hirtella, A. humistrata, A. hypoleuca, A. incarnata, A. involucrata, A. labriformis, A. lanceolata, A. lanuginosa, A. latifolia, A. lemmonii, A. linaria, A. linearis, A. longifolia, A. macrosperma, A. macrotis, A. meadii, A. michauxii, A. nummularia, A. nyctaginifolia, A. obovata, A. oenotheroides, A. ovalifolia, A. pedicellata, A. perennis, A. prostrata, A. pumila, A. purpurascens, A. quadrifolia, A. quinquedentata, A. rubra, A. rusbyi, A. ruthiae, A. sanjuanensis, A. scaposa, A. solanoana, A. speciosa, A. sperryi, A. stenophylla, A. subulata, A. subverticillata, A. sullivantii, A. syriaca, A. texana, A. tomentosa, A. tuberosa, A. uncialis, A. variegata, A. verticillata, A. vestita, A. viridiflora, A. viridis, A. viridula, A. welshii
A. albicans, A. amplexicaulis, A. angustifolia, A. arenaria, A. asperula, A. brachystephana, A. californica, A. cinerea, A. connivens, A. cordifolia, A. cryptoceras, A. curassavica, A. curtissii, A. cutleri, A. eastwoodiana, A. elata, A. engelmanniana, A. eriocarpa, A. erosa, A. exaltata, A. fascicularis, A. feayi, A. hallii, A. hirtella, A. humistrata, A. hypoleuca, A. incarnata, A. involucrata, A. labriformis, A. lanceolata, A. lanuginosa, A. latifolia, A. lemmonii, A. linaria, A. linearis, A. longifolia, A. macrosperma, A. macrotis, A. meadii, A. michauxii, A. nummularia, A. nyctaginifolia, A. obovata, A. oenotheroides, A. ovalifolia, A. pedicellata, A. perennis, A. prostrata, A. pumila, A. purpurascens, A. quadrifolia, A. quinquedentata, A. rubra, A. rusbyi, A. ruthiae, A. sanjuanensis, A. scaposa, A. solanoana, A. speciosa, A. sperryi, A. stenophylla, A. subulata, A. subverticillata, A. sullivantii, A. syriaca, A. texana, A. tomentosa, A. tuberosa, A. uncialis, A. variegata, A. verticillata, A. vestita, A. viridiflora, A. viridis, A. viridula, A. welshii
Synonyms Acerates cordifolia, Gomphocarpus cordifolius Podostemma emoryi
Name authority (Bentham) Jepson: Fl. W. Calif., 384. (1901) (Greene) Vail in J. K. Small: Fl. S.E. U.S., 948. (1903)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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