Flora of North America species comparison

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Asclepias brachystephana

Asclepias perennis

bract milkweed, short-crowned milkweed, shortcrown milkweed

aquatic milkweed, aquatic or white swamp or swamp or thin-leaf milkweed
Habit Herbs. Subshrubs or herbs, cespitose.
Stems

4–25, erect, unbranched or branched near base, 20–40 cm, tomentulose, not glaucous, rhizomes absent.

1–5, erect, sparsely to moderately branched, especially towards base, 30–60 cm, puberulent with curved trichomes in a line to glabrate, not glaucous, rhizomatous.
Leaves

opposite to subopposite, petiolate, with 1 or 2 stipular colleters on each side of petiole;

petiole 2–8 mm, tomentulose;

blade linear-lanceolate, 5–15 × 0.3–1.3 cm, chartaceous, base cuneate to rounded, margins often obscurely crisped, apex acute, mucronate, venation brochidodromous, surfaces tomentulose to glabrate, midvein puberulent with curved trichomes, margins minutely ciliate, laminar colleters absent.

persistent or gradually caducous from the base, opposite, petiolate, with 1 or 2 stipular colleters on each side of petiole on a ciliate interpetiolar ridge;

petiole 10–12 mm, ciliate;

blade narrowly elliptic to oval or oblong, 5–14 × 0.3–3 cm, membranous or chartaceous, base cuneate, margins entire, apex acute to attenuate or acuminate, minutely mucronate, venation faintly brochidodromous to eucamptodromous, surfaces sparsely puberulent with curved trichomes, more densely on veins, to glabrate, margins inconspicuously ciliate, laminar colleters absent.
Inflorescences

extra-axillary, pedunculate, 4–15-flowered;

peduncle 0.2–1.5 cm, tomentose, with 1 caducous bract at the base of each pedicel.

extra-axillary at upper nodes, sometimes appearing terminal, pedunculate, 12–30-flowered;

peduncle 1.5–5 cm, puberulent with curved trichomes, sometimes only on 1 side, with 1 caducous bract at the base of each pedicel.
Pedicels

9–15 mm, tomentose.

7–13 mm, puberulent with curved trichomes, sometimes only on 1 side.
Flowers

erect;

calyx lobes ovate-lanceolate, 2–3 mm, apex acute, tomentulose;

corolla red-violet, sometimes green with red tinge, lobes reflexed, ovate, 4–6 mm, apex acute, minutely pilosulous;

gynostegium subsessile;

fused anthers brown, cylindric, 2–2.5 mm, wings right-triangular, closed, apical appendages ovate;

corona segments red-violet to pink basally, white apically, sessile, tubular, 1.5–2 mm, greatly exceeded by style apex, apex truncate, oblique, with a proximal tooth on each side, glabrous, internal appendage lingulate, slightly exserted, sharply inflexed towards gynostegium, glabrous;

style apex shallowly depressed, red-violet.

erect to spreading;

calyx lobes narrowly lanceolate to linear, 1.2–1.5 mm, apex acute, puberulent with curved trichomes;

corolla white to pink-tinged, lobes reflexed with spreading tips, elliptic, 3–4 mm, apex acute to obtuse, glabrous abaxially, minutely papillose at base adaxially;

gynostegial column 0.8–1.2 mm;

fused anthers brown, cylindric, 1.5–2 mm, wings narrowly right-triangular, closed, apical appendages deltoid;

corona segments white, sometimes faintly pink-tinged, stipitate, tubular, dorsally rounded, 1.5–2.5 mm, slightly exceeding style apex, apex obtuse to acute, glabrous, internal appendage acicular, exserted, arching over style apex, glabrous;

style apex shallowly depressed, white, sometimes pink-tinged.
Seeds

oval to ovate, 6–7 × 4–6 mm, margin winged, faces papillate-tomentulose with dendritic scales;

coma 2–2.5 cm.

broadly oval, 12–15 × 11–14 mm, margin broadly winged, faces smooth;

coma absent.
Follicles

erect on upcurved pedicels, lance-ovoid, 5–7 × 1.2–1.8 cm, apex acuminate, shallowly ribbed, conspicuously striate, tomentulose.

pendulous on declined pedicels, lance-ovoid, 4–7 × 1–2.5 cm, apex long-acuminate, smooth, glabrous.

Asclepias brachystephana

Asclepias perennis
Phenology Flowering Apr–Sep(–Oct); fruiting (May–)Jun–Oct. Flowering (Mar–)Apr–Nov; fruiting Jun–Dec.
Habitat Plains, bajadas, pastures, arroyos, stream banks, ripar­ian areas, limestone, igneous substrates, alluvium, gravel, clay, silty, and sandy soils, desert grasslands, desert scrub, oak-juniper, juniper, and mesquite woodlands. Swamps, streamsides, ditches, bottomlands, flood plains, marshes, saturated or inundated clay, silty, and sandy soils, pine-oak, oak, and mixed hardwood for­ests, riparian woods, pine flatwoods.
Elevation 900–1900 m. (3000–6200 ft.) 0–300(–500?) m. (0–1000(–1600?) ft.)
Distribution
from FNA
AZ; NM; TX; Mexico (Aguascalientes, Chihuahua, Coahuila, Durango, Nuevo León, Sonora, Zacatecas)
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; FL; GA; IL; IN; KY; LA; MO; MS; SC; TN; TX
[WildflowerSearch map]
[BONAP county map]
Discussion

Asclepias brachystephana is a blue-gray, bushy herb with ascending foliage, few-flowered umbels of small, red and white flowers, and conspicuously striped follicles. It is unlike any other milkweed. Nonetheless, herbarium specimens are commonly confused with those of A. asperula because the herbage of A. brachystephana turns green on drying, and the leaves of A. asperula subsp. asperula are often of similar size and shape. However, leaf arrangement in A. asperula is alternate rather than opposite. The flowers of A. brachystephana are remarkably similar to, and convergent with, those of A. cutleri, A. eastwoodiana, A. ruthiae, A. sanjuanensis, and A. uncialis (M. Fishbein et al. 2011). In Arizona, A. brachystephana is restricted to the portion of the southeastern corner of the state with Chihuahuan floristic affinities, in Cochise, Graham, Pima, and Santa Cruz counties.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Asclepias perennis is the most hydrophytic North American milkweed and is often found emerging from standing water in swamps and ditches. The pendulous fruits and hairless seeds are distinctive; it is the only milkweed in the United States with seeds lacking a coma, and only one of three such species in North America. It is widely distributed along the coastal plain; inland (Arkansas, Illinois, Indiana, Kentucky, Missouri, Tennessee), it is restricted to the valleys of the Mississippi and Ohio rivers and their tributaries.

(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
A. albicans, A. amplexicaulis, A. angustifolia, A. arenaria, A. asperula, A. californica, A. cinerea, A. connivens, A. cordifolia, 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. 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. 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
Name authority Engelmann ex Torrey in W. H. Emory: Rep. U.S. Mex. Bound. 2(1): 163. (1859) Walter: Fl. Carol., 107. (1788)
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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