Prenanthes alba

Linnaeus

Sp. Pl. 2: 798. 1753.

Common names: White rattlesnakeroot prenanthe blanche
Endemic
Synonyms: Nabalus albus (Linnaeus) Hooker
Treatment appears in FNA Volume 19. Treatment on page 266. Mentioned on page 265.

Plants 20–175 cm; taproots short and thickened, fibrous. Stems erect, often mottled purple or nearly all purple (often with stout bases, 8–12 mm diam.), proximally glabrous, tomentulose distally. Leaves: proximal present at flowering; petioles narrowly winged (to 18 cm); blades usually ovate to triangular or cordate, 4–30 × 3–18 cm, thin to coriaceous, bases often hastate, margins usually coarsely dentate or serrate, sometimes deeply 3-lobed or parted, lobes acute, faces glabrous adaxially, pale to whitish and sometimes hirsute abaxially; distal reduced. Heads (3–8, in clusters) in paniculiform arrays (densest near apices). Involucres cylindric to campanulate, 13–15 × 3–5 mm. Calyculi of 5–7, triangular to lanceolate bractlets 1–3 mm, glabrous. Phyllaries (6–) 8 (–9), ± purplish or maroon, lanceolate, 10–13 mm, margins scarious, minutely ciliate, apices acute, faces glabrous. Florets 7–9 (–13); corollas whitish to pale-pink, lavender or red, 9–15 mm. Cypselae brown or tan, elliptical to linear, 3.5–6 mm; pappi usually reddish-brown, sometimes rusty, rarely yellowish, 6–7 mm. 2n = 32.


Phenology: Flowering Aug–Oct.
Habitat: Sandy oak-scrub, open oak-hickory woods, deciduous forests, dunes, creek banks, road cuts
Elevation: 100–200 m

Distribution

V19-360-distribution-map.gif

Man., Ont., Que., Sask., Ark., Conn., Del., Ga., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mo., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Pa., R.I., S.Dak., Tenn., Vt., Va., W.Va., Wis.

Discussion

Prenanthes alba is recognized by the purplish stems, relatively large, coarse, ovate or triangular leaves, relatively long, winged petioles, glabrous and often purple phyllaries, and usually reddish brown pappi. The leaves are variable, occasionally deeply 3-lobed. W. L. Milstead (1964) recognized specimens with a pale yellow pappi as “subsp. pallida,” distributed on the east coast in New Jersey, Virginia, and North Carolina. Because pappus color tends to fade somewhat on herbarium specimens, that character is difficult to assess on older specimens. The name was not validly published.

Selected References

None.

Lower Taxa

None.

No values specified."fine" is not a number.

... more about "Prenanthes alba"
not beaked +  and truncate +
scarious +
ovate +  and lanceolate +
paniculiform +
indeterminate +  and determinate +
David J. Bogler +
Linnaeus +
hastate +
compound +  and simple +
4 cm40 mm <br />0.04 m <br /> (30 cm300 mm <br />0.3 m <br />) +
usually ovate;triangular or cordate +
coriaceous +
tuberculate +, rugose +, muricate +  and smooth +
triangular;linear-lanceolate or subulate +
0.1 cm1 mm <br />0.001 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
filiform +
White rattlesnakeroot +  and prenanthe blanche +
zygomorphic +, actinomorphic +  and (3-)5-merous +
whitish +  and pale-pink lavender or red +
0.9 cm9 mm <br />0.009 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
tan +  and brown +
fusiform +  and oblanceoloid or oblong +
Man. +, Ont. +, Que. +, Sask. +, Ark. +, Conn. +, Del. +, Ga. +, Ill. +, Ind. +, Iowa +, Ky. +, Maine +, Md. +, Mass. +, Mich. +, Minn. +, Mo. +, N.H. +, N.J. +, N.Y. +, N.C. +, N.Dak. +, Ohio +, Pa. +, R.I. +, S.Dak. +, Tenn. +, Vt. +, Va. +, W.Va. +  and Wis. +
100–200 m +
pale;whitish +
glabrous +  and hirsute +
winged +  and beaked +
dispersed +
Sandy oak-scrub, open oak-hickory woods, deciduous forests, dunes, creek banks, road cuts +
indeterminate +
each +  and sessile +
0.2 cm2 mm <br />0.002 m <br /> (1.4 cm14 mm <br />0.014 m <br />) +
1.3 cm13 mm <br />0.013 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
cylindric;campanulate +
0.3 cm3 mm <br />0.003 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
sessile +  and petiolate +
cauline +  and basal +
serrate +  and dentate +
parted +  and 3-lobed +
2-carpellate +
yellowish +, rusty +  and reddish-brown +
persistent +
0.6 cm6 mm <br />0.006 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
Flowering Aug–Oct. +
connate +  and distinct +
subequal +  and unequal +
1 cm10 mm <br />0.01 m <br /> (1.3 cm13 mm <br />0.013 m <br />) +
exalbuminous +
nearly +  and mottled purple +
tomentulose +  and glabrous +
1 +  and 5 +
appendaged +  and truncate +
papillate +
Nabalus albus +
Prenanthes alba +
Prenanthes +
species +
dentate +, serrate +  and entire +
5 cm50 mm <br />0.05 m <br /> (250 cm2,500 mm <br />2.5 m <br />) +