Nabalus trifoliolatus

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Nabalus trifoliolatus

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Common names

English (Northern America): Three-leaved rattlesnakerootA, Threeleaved rattlesnakerootB; French (Northern America): Prenanthe trifolioléeA, prenanthe trifolioléeB


Plants 10-150 cm; taproots thick, with lateral roots. Stems erect, green or sometimes mottled purple, usually glabrous, sometimes tomentulose distally. Leaves: proximal usually present at flowering; petiolate (petioles winged, 1-25 cm); blades deltate to ovate, 3-12 x 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. Heads (2-7, nodding, in irregular clusters) in racemiform or paniculiform arrays. Involucres narrowly campanulate (bases attenuate to bracteates peduncles), 10-13 x 4-5 mm. Calyculi of 5-7, green to dark green or blackish, triangular bractlets 1-3 mm, glabrous. Phyllaries 7-10, green to dark green or blackish proximally, lanceolate to elliptic, 10-11 mm, margins scarious, sometimes ciliate, faces glabrous. Florets 8-13; corollas pale yellow, 9-15 mm. Cypselae tan to brown, subcylindric, subterete to angled, 4-5 mm, distinctly 8-11-ribbed; pappi pale yellow, 7-9 mm. 2n = 16.

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.

from: Bogler, D. J. 2006: 46. Prenanthes Linnaeus. - Pp. 264-271 in: Flora of North America Editorial Com. (ed.), Flora of North America 19. – New York / Oxford. (as Prenanthes trifoliata)


Northern America: ConnecticutnativeC; Georgia, U.S.A.nativeC; IndiananativeC; KentuckynativeC; LabradornativeA,C; MainenativeC; MarylandnativeC; MassachusettsnativeC; MichigannativeC; New BrunswicknativeA,C; New HampshirenativeC; New JerseynativeC; New YorknativeC; Newfoundland (NewfoundlandnativeA,C, St.Pierre-MiquelonnativeA,C); North CarolinanativeC; Nova ScotianativeA,C; OhionativeC; Ontariodoubtfully presentC; PennsylvanianativeC; Prince Edward I.nativeA,C; QuébecnativeA,C; Rhode I.nativeC; South CarolinanativeC; TennesseenativeC; VermontnativeC; VirginianativeC; West VirginianativeC


A. Brouillet L., Coursol F., Favreau M. & Anions M., VASCAN, the Database of Vascular Plants of Canada
B. Bogler D. J. - 46. Prenanthes in Flora of North America Editorial Committee (ed.), Flora of North America. North of Mexico 19. 2006
C. Bogler D. J. - 46. Prenanthes in Flora of North America Editorial Committee (ed.), Flora of North America. North of Mexico 19. 2006 (as Prenanthes trifoliolata (Cass.) Fernald)