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glaucous rattlesnakeroot, glaucous white lettuce, prenanthe à grappe, purple rattlesnake-root

dwarf rattlesnakeroot, gall of the earth, prenanthe trifoliolée, threeleaf rattlesnakeroot

Habit Plants 30–175 cm; taproots fusiform, tuberous. Plants 10–150 cm; taproots thick, with lateral roots.
Stems

erect, green or light purple, simple, (stout), glabrous and glaucous proximally, setose or hispid distally.

erect, green or sometimes mottled purple, usually glabrous, sometimes tomentulose distally.

Leaves

proximal usually present at flowering;

petioles broadly winged, (1–15 cm);

blades broadly oblanceolate to spatulate, 4–25 × 1–8 cm, coriaceous, bases attenuate, clasping, margins entire or weakly denticulate, apices obtuse or rounded, faces glabrous;

mid cauline sessile, clasping;

distal sessile and reduced.

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.

Involucres

campanulate, 11–12 × 4–7 mm.

narrowly campanulate (bases attenuate to bracteate peduncles), 10–13 × 4–5 mm.

Florets

9–29;

corollas usually pinkish, sometimes white or lavender, 7–13 mm.

8–13;

corollas pale yellow, 9–15 mm.

Phyllaries

7–14, green to purple, lanceolate to linear, 10–12 mm, margins scarious, sparsely to densely setose.

7–10, green to dark green or blackish proximally, lanceolate to elliptic, 10–11 mm, margins scarious, sometimes ciliate, faces glabrous.

Calyculi

of 8, dark green to purple, narrowly triangular-subulate bractlets 2–4 mm, coarsely setose.

of 5–7, green to dark green or blackish, triangular bractlets 1–3 mm, glabrous.

Heads

(ascending) in (elongate) narrowly racemiform or paniculiform arrays.

(2–7, nodding, in irregular clusters) in racemiform or paniculiform arrays.

Cypselae

golden brown, sub-cylindric, subterete, 5–6 mm, indistinctly 8–12-ribbed;

pappi pale yellow, 6–7 mm.

tan to brown, subcylindric, subterete to angled, 4–5 mm, distinctly 8–11-ribbed;

pappi pale yellow, 7–9 mm.

2n

= 16.

= 16.

Prenanthes racemosa

Prenanthes trifoliolata

Phenology Flowering Aug–Sep. Flowering Aug–Oct.
Habitat Sandy alluvial soils of stream banks, wet meadows, tall-grass prairies, fens, marshy flats, bogs (mainly calcicolous, at least in north) Moist oak-hickory woods, swampy thickets, sandy areas, cliffs, sometimes saline habitats
Elevation 0–2800 m (0–9200 ft) 0–1400 m (0–4600 ft)
Distribution
from FNA
CO; IA; IL; IN; KY; ME; MI; MN; MO; MT; ND; NE; NJ; NY; OH; PA; SD; VT; WA; WI; WY; AB; BC; MB; NB; NF; NS; ON; QC; SK
[WildflowerSearch map]
from FNA
CT; GA; IN; KY; MA; MD; ME; MI; NC; NH; NJ; NY; OH; PA; RI; SC; TN; VA; VT; WV; NB; NL; NS; ON; PE; QC; SPM
[WildflowerSearch map]
Discussion

Prenanthes racemosa is recognized by its erect, stout, simple habit, glaucous stems, spatulate proximal leaves with broadly winged petioles and rounded to obtuse apices, heads borne in narrow racemiform arrays, purple and hairy phyllaries, and usually pinkish corollas. It is most similar to P. aspera, which differs in its generally smaller stature, more hirsute stems, leaves that are hispid abaxially, proximal leaves usually withered by flowering, and creamy white or yellow corollas. Hybrids between P. racemosa and P. trifoliolata, known as P. ×mainensis, occur in the northeastern United States and southeastern Canada (see discussion under P. trifoliolata).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

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.)

Source FNA vol. 19, p. 269. FNA vol. 19, p. 271.
Parent taxa Asteraceae > tribe Cichorieae > Prenanthes Asteraceae > tribe Cichorieae > Prenanthes
Sibling taxa
P. alata, P. alba, P. altissima, P. aspera, P. autumnalis, P. barbata, P. boottii, P. carrii, P. crepidinea, P. roanensis, P. sagittata, P. serpentaria, P. trifoliolata
P. alata, P. alba, P. altissima, P. aspera, P. autumnalis, P. barbata, P. boottii, P. carrii, P. crepidinea, P. racemosa, P. roanensis, P. sagittata, P. serpentaria
Synonyms Nabalus racemosus, P. racemosa subsp. multiflora, P. racemosa var. pinnatifida Nabalus trifoliolatus, P. trifoliolata var. nana
Name authority Michaux: Fl. Bor.-Amer. 2: 84. (1803) (Cassini) Fernald: Contr. Bot. Vermont 8: 89. (1900)
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