Asclepias tuberosa
Asclepias lanceolata
asclépiade tubéreuse, butterfly milkweed
few-flower milkweed, smooth-orange milkweed
1–numerous, erect to ascending, branched in inflorescence, 15–90 cm, densely hirsute, not glaucous, rhizomes absent.
1, erect, unbranched, 60–125 cm, glabrous, 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 or petiolate, with 1 stipular colleter on each side of petiole on a ciliate interpetiolar ridge;
petiole 0–1 mm, ciliate;
blade linear to linear-lanceolate, somewhat conduplicate, 7–25 × 0.2–1.7 cm, chartaceous, base cuneate, margins entire, apex attenuate, mucronate, venation faintly brochidodromous to obscure, surfaces glabrous, margins inconspicuously ciliate, 8–12 laminar colleters, usually obscured by conduplicate petiole.
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 often extra-axillary at an upper node, usually branched, pedunculate, 4–16-flowered;
peduncle 1–7.5 cm, puberulent on 1 side with curved trichomes, with 1 caducous bract at the base of each pedicel.
9–24 mm, puberulent with curved trichomes to pilosulous.
13–19 mm, puberulent on 1 side 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 narrowly lanceolate, 2–3 mm, apex acute, puberulent with curved trichomes to glabrate;
corolla red, lobes reflexed, usually with spreading tips, elliptic, 9–10 mm, apex acute, glabrous abaxially, minutely papillose at base adaxially;
gynostegial column 1.5–2 mm;
fused anthers green, tinged yellow to red, truncately obconic, 2.5 mm, wings narrowly right-triangular, slightly open at base, apical appendages deltoid;
corona segments yellow to reddish orange, stipitate, broadly tubular, dorsally flattened, 5–6 mm, exceeding style apex, apex obtuse, flared, glabrous, internal appendage subulate, exserted, sharply inflexed over style apex, glabrous;
style apex shallowly depressed, red.
ovate, 8–9 × 4–5 mm, margin winged, faces minutely rugulose;
coma 3–5 cm.
broadly oval, 8–10 × 6–8 mm, margin winged, faces smooth;
coma 3–3.5 cm.
erect on upcurved pedicels, fusiform, 7–14 × 1.2–2 cm, apex long-acuminate or attenuate, smooth, hirsute.
erect on upcurved pedicels, narrowly fusiform, 5.5–10 × 0.8–1 cm, apex attenuate to long-acuminate, smooth, sparsely pilosulous or puberulent with curved trichomes to glabrate.
= 22.
Asclepias tuberosa
Asclepias lanceolata
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 lanceolata is a characteristic wetland milkweed of the Atlantic and Gulf coastal plains, where it occurs sometimes with its similar relative, A. rubra. It is distinguished from A. rubra by flower color (shades of orange, yellow, and red versus pink, lavender, and reddish purple), corona segment apex (obtuse versus acute), and leaf shape (linear to linear-lanceolate versus narrowly lanceolate to ovate). These species are known to hybridize locally, particularly in North Carolina, and putative hybrids can be recognized by intermediate floral and vegetative traits. The pattern of yellow-orange coronas paired with red corollas is similar to that of the introduced A. curassavica, and these species are sometimes confused. Asclepias curassavica differs by usually pure yellow (versus orangish) coronas, more flowers per umbel, much shorter peduncles, and wider, shorter leaf blades. Asclepias lanceolata sometimes is confused also with orange-flowered A. tuberosa, although that species only rarely has bicolored flowers, and the two are quite distinct in habitat, growth form, and vestiture. Through habitat loss, A. lanceolata has become quite rare in some areas, particularly the northeastern United States. It is considered to be of conservation concern in Delaware (Sussex County), Maryland (Dorchester County), and New Jersey. It has been reported, but not documented, from Tennessee, and its occurrence there seems unlikely. The report may be based on confusion with the name of the formerly recognized (and unrelated) A. viridiflora var. lanceolata.
(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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