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

barbed rattlesnakeroot

Habit Plants 30–175 cm; taproots fusiform, tuberous. Plants 50–150 cm; taproots thickened, tuberous, with lateral side roots.
Stems

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

erect, purplish, glabrous proximally, finely tomentulose or setose 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 withered by flowering; petiolate (petioles 2–3 cm, winged);

blades ± elliptic, 4–10 × 1–4 cm, coriaceous, bases narrowed (not hastate), margins coarsely and irregularly dentate or serrate (unlobed), apices acute, faces glabrous or papillose-hispid;

mid cauline cuneate or sessile and clasping;

distal sessile and reduced.

Involucres

campanulate, 11–12 × 4–7 mm.

cylindric to campanulate, 12–16 × 4–6 mm.

Florets

9–29;

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

10–15;

corollas white to yellowish white, 13–16 mm.

Phyllaries

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

6–8, usually purple or lavender, subulate to lanceolate, 11–14 mm, margins scarious, coarsely hispid or setose along midveins.

Calyculi

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

of 7–11, dark green to purple, triangular to lance-ovate bractlets 2–5 mm, hispid or setose along midveins.

Heads

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

(15–50) in (much-branched) paniculiform or thyrsiform arrays (nodding).

Cypselae

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

pappi pale yellow, 6–7 mm.

tan, subcylindric, subterete to 5-angled, 8–10 mm, indistinctly 8–10-ribbed;

pappi yellowish white, 7–8 mm.

2n

= 16.

Prenanthes racemosa

Prenanthes barbata

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) Sandy oak-hickory-pine woods, savannas, prairies, pine barrens
Elevation 0–2800 m (0–9200 ft) 10–100 m (0–300 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
AL; AR; GA; KY; LA; OK; TN; TX
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 barbata is identified by its erect habit, irregularly dentate leaves, heads with 6–8 purple phyllaries, coarsely setose calyculi and phyllaries, and white to yellowish white corollas.

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

Source FNA vol. 19, p. 269. FNA vol. 19, p. 267.
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. boottii, P. carrii, P. crepidinea, P. racemosa, P. roanensis, P. sagittata, P. serpentaria, P. trifoliolata
Synonyms Nabalus racemosus, P. racemosa subsp. multiflora, P. racemosa var. pinnatifida Nabalus fraseri var. barbatus, P. serpentaria var. barbata
Name authority Michaux: Fl. Bor.-Amer. 2: 84. (1803) (Torrey & A. Gray) Milstead ex Cronquist: Brittonia 29: 223. (1977)
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