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glaucous white lettuce, purple rattlesnake-root

Habit Plants 30–175 cm; taproots fusiform, tuberous.
Stems

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

Heads

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

Involucres

campanulate, 11–12 × 4–7 mm.

Florets

9–29;

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

Phyllaries

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

Calyculi

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

Cypselae

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

pappi pale yellow, 6–7 mm.

2n

= 16.

Prenanthes racemosa

Phenology Flowering Aug–Sep.
Habitat Sandy alluvial soils of stream banks, wet meadows, tall-grass prairies, fens, marshy flats, bogs (mainly calcicolous, at least in north)
Elevation 0–2800 m [0–9200 ft]
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.)

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
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Parent taxa 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
Synonyms Nabalus racemosus, P. racemosa subsp. multiflora, P. racemosa var. pinnatifida
Name authority Michaux: Fl. Bor.-Amer. 2: 84. (1803)
Source Flora of North America vol. 19, p. 269.
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