Prenanthes trifoliolata
Prenanthes alata
dwarf rattlesnakeroot, gall of the earth, prenanthe trifoliolée, threeleaf rattlesnakeroot
western rattlesnake-root, white or western white lettuce, wing-leaf rattlesnakeroot
erect, green or sometimes mottled purple, usually glabrous, sometimes tomentulose distally.
1(–10), erect or ascending, green to purple, usually simple, glabrous or glabrate proximally, tomentulose distally.
proximal usually present at flowering; petiolate (petioles winged, 1–25 cm);
blades deltate to ovate, 3–12 × 1–15 cm, thin, bases cordate to rounded, margins palmately 3(–5)-lobed to -divided (then leaves compound), lobes and sinuses usually angular (not rounded), lobes short and lanceolate, ultimate margins irregularly serrate, faces glabrous or ciliate along abaxial veins and margins;
distal reduced, palmately lobed or entire.
proximal present at flowering;
petioles winged (2–6 cm);
blades triangular to irregularly elliptic, 3–25 × 1–7 cm, thin or slightly coriaceous, bases abruptly constricted, truncate to slightly hastate, margins irregularly dentate or coarsely serrate, apices acute to acuminate, faces glabrate;
distal sessile, ovate to lanceolate, reduced.
narrowly campanulate (bases attenuate to bracteate peduncles), 10–13 × 4–5 mm.
narrowly campanulate, 10–13 × 5–6 mm.
8–13;
corollas pale yellow, 9–15 mm.
7–16;
corollas white to purplish, 9–16 mm.
7–10, green to dark green or blackish proximally, lanceolate to elliptic, 10–11 mm, margins scarious, sometimes ciliate, faces glabrous.
8, green to dark green, lanceolate, 8–11 mm, margins scarious, apices acute, finely tomentulose.
of 5–7, green to dark green or blackish, triangular bractlets 1–3 mm, glabrous.
of 2–3, dark green, lanceolate or subulate bractlets 1–3 mm, glabrous or finely tomentulose.
(2–7, nodding, in irregular clusters) in racemiform or paniculiform arrays.
(10–17) in broad, corymbiform arrays, lateral branches often elongate and overtopping main stems.
tan to brown, subcylindric, subterete to angled, 4–5 mm, distinctly 8–11-ribbed;
pappi pale yellow, 7–9 mm.
brown to light tan, subcylindric, 4–7 mm, weakly 7–10-ribbed;
pappi pale yellow to dull white, 8–10 mm.
= 16.
= 16.
Prenanthes trifoliolata
Prenanthes alata
Prenanthes trifoliolata is recognized by its relatively large, palmately 3–5-lobed leaves with angular lobes and sinuses, basally attenuate involucres, dark green and glabrous calyculi and phyllaries, and pale yellow corollas. Dwarf plants with deeply parted leaves found in alpine areas of northern New England and Canada have been recognized as P. nana or P. trifoliolata var. nana. This form is probably no more than a phenotypic adaptation to harsh environments. In at least some localities, it intergrades with more typical P. trifoliolata at lower elevations.
Hybrids between Prenanthes trifoliolata and P. racemosa, known as P. ×mainensis A. Gray, have been found in Maine, New Brunswick, Nova Scotia, and southern Quebec, usually where the two parents come together in cliff or saline habitats. The leaves of the hybrids are intermediate between 3-lobed and spatulate, the distal are sessile, the heads are nodding, and the phyllaries are glabrous, as in the P. trifoliolata parent.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Prenanthes alata is recognized by its relatively small size, elongate and winged petioles, triangular-hastate leaf blades, heads in broad corymbiform arrays, and dark green, finely tomentulose phyllaries.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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