Asclepias tuberosa
Asclepias pedicellata
asclépiade tubéreuse, butterfly milkweed
savanna milkweed, savannah milkweed
1–numerous, erect to ascending, branched in inflorescence, 15–90 cm, densely hirsute, not glaucous, rhizomes absent.
1, erect, unbranched, 10–45 cm, puberulent with curved trichomes, not glaucous, rhizomes absent.
alternate, petiolate, with 1 or 2 stipular colleters on each side of petiole;
petiole 1–4 mm, densely hirsute;
blade elliptic, oblong, or oblanceolate to lanceolate or linear, 2–12 × 0.3–3 cm, chartaceous, base cuneate or obtuse to rounded, truncate, hastate, or cordate, margins entire, apex acute to attenuate or obtuse to rounded, venation brochidodromous to eucamptodromous, surfaces hirsute, more densely so on midvein abaxially, margins ciliate, 0–4 laminar colleters.
opposite, sessile, with 1 stipular colleter on each side of leaf base;
blade linear to narrowly elliptic or narrowly lanceolate, 1.5–6 × 0.1–0.8 cm, chartaceous, base cuneate, margins entire, apex acute, mucronate, venation obscure to eucamptodromous, surfaces puberulent with curved trichomes or scabridulous to glabrate, margins ciliate, 2 laminar colleters.
corymbs of extra-axillary umbels on branches, sessile or pedunculate, 5–27-flowered;
peduncle 0–4 cm, sometimes branched, hirsute, with 1 caducous bract at the base of each pedicel.
terminal and extra-axillary at upper nodes, pedunculate, 2–7-flowered;
peduncle 0.15–1 cm, densely puberulent with curved trichomes, with 1 caducous bract at the base of each pedicel.
9–24 mm, puberulent with curved trichomes to pilosulous.
5–13 mm, minutely puberulent with curved trichomes.
erect;
calyx lobes narrowly lanceolate, 2–3 mm, apex acute, hirsute to puberulent with curved trichomes;
corolla reddish orange (nearly red) to orange or yellow, lobes reflexed with spreading tips, narrowly elliptic, (5–)6–8 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially;
gynostegial column 1.2–1.5 mm, fused anthers yellow to yellowish green, cylindric, 2–3 mm, wings right-triangular, closed, apical appendages ovate;
corona segments reddish orange (nearly red) to orange or yellow, substipitate, conduplicate, dorsally flattened, sulcate, 5.5–7 mm, greatly exceeding style apex, apex acute, glabrous, internal appendage subulate, exserted, arching above style apex, glabrous;
style apex shallowly depressed, yellow to yellowish green.
erect;
calyx lobes elliptic, 2–3 mm, apex acute, sparsely puberulent with curved trichomes to glabrate;
corolla yellowish green to green, lobes erect, mostly concealing corona, narrowly elliptic, 7–10 mm, apex acute, glabrous;
gynostegial column 4–6 mm;
fused anthers green, broadly conic, 1–1.5 mm, wings right-triangular with decurrent base, closed, apical appendages ovate;
corona segments yellowish green to green, sometimes dark green at apex, sessile, conduplicate, 1.5–2.5 mm, greatly exceeded by style apex, apex incurved, rounded, glabrous, internal appendage absent;
style apex flat, green.
ovate, 8–9 × 4–5 mm, margin winged, faces minutely rugulose;
coma 3–5 cm.
ovate, 5–6 × 3–4 mm, margin winged, faces sparsely and minutely rugulose;
coma 2–2.5 cm.
erect on upcurved pedicels, fusiform, 7–14 × 1.2–2 cm, apex long-acuminate or attenuate, smooth, hirsute.
erect on straight pedicels, fusiform, 8–14 × 0.3–0.5 cm, apex long-attenuate, smooth, densely puberulent with curved trichomes.
= 22.
Asclepias tuberosa
Asclepias pedicellata
Subspecies 3 (3 in the flora).
Asclepias tuberosa is one of the most familiar and beloved North American milkweeds and is a favored element of pollinator gardens because of the cheery orange flowers that attract abundant insect visitors. The clear latex is unusual in the genus and is often commented upon by collectors. The subspecies of A. tuberosa are highly intergrading. It is often difficult to satisfactorily place a given specimen in a particular subspecies; however, the great majority are readily assigned. It appears that the conspicuous variation in leaf morphology across the subspecies corresponds to genetically structured population variation (R. E. Woodson Jr. 1947). However, it is unknown to what extent cultivation and other human activities have blurred the distinctions among the geographic variants. Future recognition of the subspecies should be supported by genetic study with modern techniques. Although yellow-flowered plants predominate in the western plains, color variation is often pronounced in single populations, and yellow flowers may be encountered anywhere in the range. Hybridization with A. syriaca is documented, but is exceedingly rare. Presumed hybrids can be recognized by intermediate floral and vegetative traits.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Asclepias pedicellata is found in drier habitats than some co-distributed milkweeds, such as A. connivens and A. viridula. It sometimes occurs in the same sites as A. cinerea, A. curtissii, and A. feayi. The erect petals and elongate gynostegial column are unique among Asclepias species in the flora area. The green flowers with hidden coronas and low stature of the plants can make them frustratingly cryptic in their grass-dominated habitats. Asclepias pedicellata is common only in Florida and North Carolina and is considered rare and of conservation concern in the intervening region in Georgia and South Carolina.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaf bases hastate, blade margins crisped. | subsp. rolfsii |
1. Leaf bases cuneate, obtuse, rounded, truncate, or subcordate, blade margins planar. | → 2 |
2. Leaf bases cuneate to obtuse, rounded, or subcordate, apices rounded to acute, mostly east of the crest of the Appalachian Mountains. | subsp. tuberosa |
2. Leaf bases truncate or obtuse to cordate, apices acute to attenuate, mostly west of the crest of the Appalachian Mountains. | subsp. interior |
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