Prenanthes serpentaria
Prenanthes alba
butterweed, cankerweed, gall-of-the-earth, lion's-foot
prenanthe blanche, white lettuce, white rattlesnake-root
erect, green to reddish or purple mottled, proximally glabrous, distally sparsely tomentulose.
erect, often mottled purple or nearly all purple (often with stout bases, 8–12 mm diam.), proximally glabrous, tomentulose distally.
proximal often withered by flowering; petiolate (petioles 1–10 cm, often with pair of lobes);
blades deltate to ovate or elliptic, 5–20 × 4–10 cm, coriaceous, margins usually deeply, pinnately 3–5-lobed, lobes and sinuses large and ± rounded, sometimes deeply cleft to base or palmately divided, apices acute or obtuse, ultimate margins entire or dentate, faces glabrous or finely tomentose on veins;
cauline sessile or petiolate;
distal reduced in size and lobing, often entire.
proximal present at flowering;
petioles narrowly winged (to 18 cm);
blades usually ovate to triangular or cordate, 4–30 × 3–18 cm, thin to coriaceous, bases often hastate, margins usually coarsely dentate or serrate, sometimes deeply 3-lobed or parted, lobes acute, faces glabrous adaxially, pale to whitish and sometimes hirsute abaxially;
distal reduced.
cylindric (often attenuate basally to bracteate peduncles), 12–15 × 4–5 mm.
cylindric to campanulate, 13–15 × 3–5 mm.
(8–)10–14(–19);
corollas usually yellow to pale yellow, 9–15 mm.
7–9(–13);
corollas whitish to pale pink, lavender or red, 9–15 mm.
(7–)8–(10), green or often purple, narrowly lanceolate to elliptic, 10–13 mm, sparsely hispid to appressed, coarsely setose, often reduced to single coarse, appressed seta (setae green or tan).
(6–)8(–9), ± purplish or maroon, lanceolate, 10–13 mm, margins scarious, minutely ciliate, apices acute, faces glabrous.
of 8–10, green to purple, triangular to subulate bractlets 1–4 mm, often tomentulose to setose.
of 5–7, triangular to lanceolate bractlets 1–3 mm, glabrous.
(6–12 in nodding clusters) in broad, paniculiform to corymbiform arrays (often widely branching and subdichotomous, at least some branches elongate).
(3–8, in clusters) in paniculiform arrays (densest near apices).
golden brown to light tan, subcylindric, subterete or angled, 5–8 mm, indistinctly 8–10-ribbed;
pappi tan, 7–8 mm.
brown or tan, elliptical to linear, 3.5–6 mm;
pappi usually reddish brown, sometimes rusty, rarely yellowish, 6–7 mm.
= 16.
= 32.
Prenanthes serpentaria
Prenanthes alba
Prenanthes serpentaria is generally recognized by its large, deeply 3–5-lobed proximal leaves with rounded sinuses and lobes, winged petioles, attenuate involucres, sparsely setose phyllaries, and yellow corollas. The leaves are variable in size and lobing, often on the same plant. Some specimens have predominantly ovate to elliptic, unlobed leaves, and these have been variously recognized. Some specimens appear to combine characteristics of P. crepidinea or P. trifoliolata and may be the result of recent or ancient hybridization. The species boundaries in this group merit further study.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Prenanthes alba is recognized by the purplish stems, relatively large, coarse, ovate or triangular leaves, relatively long, winged petioles, glabrous and often purple phyllaries, and usually reddish brown pappi. The leaves are variable, occasionally deeply 3-lobed. W. L. Milstead (1964) recognized specimens with a pale yellow pappi as “subsp. pallida,” distributed on the east coast in New Jersey, Virginia, and North Carolina. Because pappus color tends to fade somewhat on herbarium specimens, that character is difficult to assess on older specimens. The name was not validly published.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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