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

Roan Mountain rattlesnakeroot

Habit Plants 30–175 cm; taproots fusiform, tuberous. Plants 18–150 cm; taproots slender or short and thickened, tuberous.
Stems

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

erect, green or purple, simple, glabrous proximally, crisply 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 present at flowering; petiolate (petioles not winged or distal narrowly winged);

blades ovate, 3–22 × 2–15 cm, coriaceous, bases cordate to truncate or rounded, margins often deeply 3–5-palmately lobed or compound, lobes and sinuses angular, ultimate margins irregularly dentate, apices acute, faces usually finely tomentulose on veins;

mid cauline short-petiolate or sessile;

distal short-petiolate or sessile, reduced, lanceolate.

Involucres

campanulate, 11–12 × 4–7 mm.

cylindric to narrowly campanulate, 12–14 × 2.5–3 mm.

Florets

9–29;

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

5–7(–13);

corollas greenish yellow, 8–10 mm.

Phyllaries

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

5–9, green or dark green, apices blackish, linear to oblanceolate, 9–11 mm, sparsely and coarsely setose.

Calyculi

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

of 4–6, blackish green, triangular to lanceolate bractlets 1–3 mm, densely setose.

Heads

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

in narrowly 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 to yellow, fusiform, subterete or angled, 4–5 mm, indistinctly 8–12-ribbed;

pappi yellow to whitish, 5–6 mm.

2n

= 16.

= 16.

Prenanthes racemosa

Prenanthes roanensis

Phenology Flowering Aug–Sep. 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) Spruce-hardwood forests, wooded slopes, open grassy summits
Elevation 0–2800 m (0–9200 ft) 1600–1700 m (5200–5600 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
NC; TN; VA
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.)

Of conservation concern.

Prenanthes roanensis is recognized by its 5–7 florets and dark setae on the phyllaries. It is found at mid to high elevations in the Blue Ridge Province of the Appalachian Mountains. It is rather variable and often confused with other species. It is considered rare or threatened throughout its range.

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

Source FNA vol. 19, p. 269. FNA vol. 19, p. 270.
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. sagittata, P. serpentaria, P. trifoliolata
Synonyms Nabalus racemosus, P. racemosa subsp. multiflora, P. racemosa var. pinnatifida Nabalus roanensis, P. cylindrica
Name authority Michaux: Fl. Bor.-Amer. 2: 84. (1803) (Chickering) Chickering: Bot. Gaz. 6: 191. (1881)
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