Prenanthes alba Linnaeus
The words or terms in red
(actually dark orange) in the text are defined in a
Prenanthes alba is a perennial,
that is between 2 to 5 feet high; it has an erect central stem and often
develops short side stems in the upper half; the stem is thick, light green
to purple (usually the latter), glabrous,
glaucous, and oozes a milky juice when
broken. The plant has short and thickened fibrous
It is native to North America. Its
chromosome number (2n) is 32.
The plant belongs to the
In Greek, πρηνησ
(prênês) means nodding and
means flower, the genus name alluding to the drooping flower heads.
In Latin, albus means white, the
epithet referring then to the color of the
ray florets of the species.
Some of the vernacular names of
Prenanthes alba are Lion's-foot, White Rattlesnakeroot,
Rattlesnake-root and White-lettuce.
The French vernacular name is Prenanthe blanche.
Prenanthes alba has also been known as:
- Nabalus albus (L.) Hook.
- Chondrilla alba (L.) Lam.
- Harpalyce alba (L.) D. Don ex Beck
- Nabalus integrifolius Cass.
- Nabalus serpentarius (Pursh) Hook. var. integrifolius
Prenanthes alba can be identified by its size, and its clusters of small
nodding flower heads, its purplish stems, its relatively large, coarse,
ovate or triangular leaves that are variable,
and occasionally deeply 3-lobed.
It can be distinguished from the other Prenanthes
in Québec by its primary bracts:
each flower head has 8 primary bracts that are
pale purple-green. In contrast, each flowerhead of Prenanthes altissima
has 5 primary bracts that are light green. Furthermore, the ray florets of
Prenanthes alba are more likely to be pale purple or lavender than those
of Prenanthes altissima. As for the leaves of Prenanthes racemosa,
they are oblanceolate to
- From 60 cm to 1.20 m high.
- Hosting clusters of flower heads.
- With a milky sap.
- Highly variable in shape, they can be
(with 3 to 5 lobes),
- The lower ones long-stalked, grossly triangular, lobed or unlobed.
- Getting simpler and smaller towards the top.
- Containing a milky white latex.
- Usually hairy below.
- In long, branched inflorescences,
panicles, each panicle with a long
ascending peduncle at its base,
which divides at its apex
into 2 to 4 short spreading branches.
- Nodding, cylindrical, with only the ray florets protruding beyond the
cylinder of the bracts.
- White, cream-coloured, or pinkish.
- About 3/4 inch long and 1/2 inch wide.
- With only ray florets, about 8 to 12 in number.
- With prominent stamens.
- With purplish glabrous phyllaries.
- Pollinated by bumblebees seeking the
- Blooming from late August to September in my area,
25 km north of Montréal.
- A brown or tan elliptical to linear
- Between 3.5 to 6 mm long.
- With a usually reddish brown, sometimes rusty, or cinnamon-brown or
yellowish pappus, about 6mm long.
Prenanthes alba habitats include rich
mesic woodlands, sandy woodlands,
bluffs, wooded slopes, rocky ravines and the base of cliffs in wooded areas,
and woodland borders. It can be found in either oak (Quercus) or
maple-basswood (Acer-Tilia) forests.
Prenanthes alba is found from New England to Iowa, and from Canada to
In Canada, it is found in Québec, Ontario, Manitoba and Saskatchewan.
The map shows the Canadian provinces and USA states where the plant can be
The Chippewa Indians used dried, powdered root of Prenanthes alba added
to food to produce postpartum milk flow.
A decoction of the root, which is bitter is said to have been successfully used
to cure the bite of the rattlesnake and also in
The Iroquois used a poultice against
dog and rattlesnake bites, hence one of the common name Rattlesnake root.
The Ojibwa used the sap especially in female diseases, as a
Even though the foliage of Prenanthes alba has a bitter taste,
it is sometimes browsed by White-Tailed Deers (Odocoileus virginianus).
The photos of the gallery were taken either with one of the following:
Minolta DiMAGE 7,
Canon PowerShot A530,
Canon Xt Rebel, usually with the EF-S60mm f/2.8 Macro USM objective,
Fujifilm A 610 and
EPSON Perfection 1650 (scanner).
The title in the window shows the date when the picture was taken,
i.e. jan_30_06... would mean that the photo was taken on the 30th of
January, the 06 is for the 6th picture taken that day.
The month, day and picture number might be followed by a letter which I use
to identify the system used to take the picture.
Click on the thumbnails to get larger view.
The original photos are usually in TIFF format,
the photos shown are generally in JPEG format,
often of dimensions one half (surface one quarter)
for loading time reduction.
The leaves were scanned at 300 dpi,
and the dimensions of the resulting picture divided by 2 (area divided by 4);
this allows to measure the dimensions of the leaves.