Asclepias cordifolia
Asclepias exaltata
heart-leaf milkweed, purple milkweed
asclépiade très grande, poke milkweed, tall milkweed
1–20, ascending to spreading, unbranched, 25–100 cm, glabrous, glaucous, rhizomes absent.
1–3+, erect, unbranched, 65–150 cm, sparsely pubescent to glabrate, not glaucous, rhizomes absent.
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 (rarely whorled at 1 midstem node), petiolate, with 1 stipular colleter on each side of petiole;
petiole 5–15 mm, minutely puberulent with curved trichomes to glabrate;
blade broadly ovate to oblong or elliptic, 10–24 × 2–11 cm, membranous, base cuneate, margins entire, apex attenuate to acuminate, venation eucamptodromous to brochidodromous, surfaces pilosulous to glabrate abaxially, sparsely pilosulous to glabrate adaxially, densely so on veins, margins ciliate, 6–10 laminar colleters (often obscured in pressed specimens).
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 (terminal), pedunculate, 11–41-flowered;
peduncle 0.5–8.5 cm, puberulent on 1 side with curved trichomes, with 1 caducous bract at the base of each pedicel.
16–37 mm, sparsely pilose.
25–45 mm, puberulent with curved trichomes to pilosulous on 1 side.
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.
spreading to drooping;
calyx lobes narrowly lanceolate, 3–4.5 mm, apex attenuate, pilosulous;
corolla green (rarely pink-tinged), lobes reflexed, sometimes with spreading tips, elliptic, 6–12 mm, apex acute, glabrous;
gynostegial column 1.5–2 mm;
fused anthers green, columnar, 2.5–3.5 mm, wings right-triangular with rounded tip, apical appendages deltoid;
corona segments white to pinkish, sometimes red-purple at base, stipitate, tubular, 3–5 mm, exceeding style apex, base saccate, apex truncate with 1–2 teeth on each side, glabrous, internal appendage falcate, exserted, arching above style apex, glabrous;
style apex shallowly depressed, green or cream.
ovate, 8–9 × 5–7 mm, margin not winged, faces reticulate-rugulose;
coma 3–3.5 cm.
lance-ovate, 8–10 × 4–6 mm, margin winged, faces minutely rugulose;
coma 2.5–3 cm.
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, 10–15 × 1.5–2 cm, apex long-acuminate, smooth, puberulent with curved trichomes.
= 22.
= 22.
Asclepias cordifolia
Asclepias exaltata
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.)
Unlike the other common deciduous forest understory milkweeds, the range of Asclepias exaltata does not extend to the Ozarks. Compared to these other species, A. exaltata seems to prefer richer soils. Non-flowering individuals are often confused with A. purpurascens, from which they are distinguished by leaves with thinner texture, sparser abaxial vestiture, and longer-tapered apices. Hybrids with A. syriaca are well established at several disjunct locations (S. R. Kephart et al. 1988), and their genetics and pollination have been studied (S. B. Broyles 2002; T. M. Stoepler et al. 2012). Hybrids with A. purpurascens and A. amplexicaulis are also known, but appear to be rare and local. Putative hybrids exhibit intermediate floral and vegetative morphology. Asclepias exaltata is rare at the margins of its range and is considered to be of conservation concern in Alabama (Lawrence, Madison, and Winston counties), Delaware (New Castle County), Rhode Island, and Quebec. Recently, it has been documented at a single site in Missouri (Cape Girardeau County) and should be considered to be of conservation concern in that state, too.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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