Prenanthes trifoliolata
Prenanthes boottii
dwarf rattlesnakeroot, gall of the earth, prenanthe trifoliolée, threeleaf rattlesnakeroot
alpine rattlesnakeroot, Boot's rattlesnakeroot
erect, green or sometimes mottled purple, usually glabrous, sometimes tomentulose distally.
decumbent to erect, mottled purple, simple, glabrous 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; petiolate (petioles 2–8 cm, not winged);
blades ovate to deltate, 2–8 × 0.5–3 cm, bases hastate or sagittate, margins entire or weakly dentate, faces glabrous;
distal reduced, elliptic to lanceolate.
narrowly campanulate (bases attenuate to bracteate peduncles), 10–13 × 4–5 mm.
cylindro-campanulate, 10–11 × 5–6 mm.
8–13;
corollas pale yellow, 9–15 mm.
9–20;
corollas white, 7–13 mm.
7–10, green to dark green or blackish proximally, lanceolate to elliptic, 10–11 mm, margins scarious, sometimes ciliate, faces glabrous.
8–11, dark green to almost black, lanceolate to subulate, 8–12 mm, faces glabrous.
of 5–7, green to dark green or blackish, triangular bractlets 1–3 mm, glabrous.
of 4–5, dark green to blackish, subulate bractlets 2–5 mm, glabrous.
(2–7, nodding, in irregular clusters) in racemiform or paniculiform arrays.
(10–20) in narrow, racemiform to thyrsiform arrays (nodding).
tan to brown, subcylindric, subterete to angled, 4–5 mm, distinctly 8–11-ribbed;
pappi pale yellow, 7–9 mm.
light tan to yellow, subcylindric, subterete to angled, 5–6 mm, indistinctly 7–10-ribbed;
pappi pale yellow, 6–8 mm.
= 16.
= 32.
Prenanthes trifoliolata
Prenanthes boottii
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.)
Of conservation concern.
Prenanthes bootii is recognized by its relatively short, decumbent habit, deltate to hastate proximal leaves, entire or weakly dentate margins, glabrous and blackish green phyllaries, white corollas, and alpine habitat.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
MD Biodiversity
MI Flora
WildflowerSearch
iNaturalist
USDA Plants Database
