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Cankerweed, Lion's Foot, Snakeweed, Earthgall, Butterweed - Prenanthes serpentaria


Family: Asteraceae - Aster family Genus Common Name: Rattlesnakeroot Native Status: NativeDicot Perennial Herb
Prenanthes serpentaria - Cankerweed, Lion's Foot, Snakeweed, Earthgall, Butterweed. Found on the eastern seaboard and Appalachian Mountain states as far south as Florida and as far west as Mississippi, Prenanthes serpentaria is Endangered in Massachusetts and a species of Special Concern in Rhode Island. The species epithet serpentaria and the genus common name Rattlesnakeroot come from the use of a tonic historically made from the roots or the milky juice of the stem as an antidote for the poison of snake bites.

There are similar Prenanthes species found in Haywood County, North Carolina, where these photos were taken. I discounted P. trifoliolata because that species has more angular leaves and fewer heads in each inflorescence. I discounted P. altissima because of the general appearance of the plant vis-a-vis photos at the USDA Plants Database, and the number of phyllaries in that species - normally five, not more than 6.

Found in:
AL, CT, DC, DE, FL, GA, KY, MA, MD, MS, NC, NH, NJ, NY, OH, PA, RI, SC, TN, VA, VT, WV

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Prenanthes serpentaria

Distribution of Prenanthes serpentaria in the United States and Canada:
USDA Plants Distribution Map temporarily unavailable.
Blue=Native; Grey=Introduced

Map from USDA Plants Database:
USDA, NRCS. 2017. The PLANTS Database (http://plants.usda.gov, 25 Jun 2017). National Plant Data Team, Greensboro, NC 27401-4901 USA.

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Site: Blue Ridge Parkway, Haywood County, NC Date: 2011-August-01Photographer: Gerald C. Williamson
Nikon D7000
Tamron SP 90MM f/2.8 AF Macro
Prenanthes have only ray florets, no disk florets. Counting ray florets and phyllaries are among the ways to differentiate between species. P. serpentaria has 8 up to 19 ray florets but usually 10 to 14, and 7 to 10, usually 8 phyllaries. P. trifoliolata 8 to 13 florets and 7 to 10 phyllaries. P. altissima normally has a count of 5 both florets and phyllaries, but may have as few as 4 or as many as 6.
Prenanthes serpentaria

Site: Blue Ridge Parkway, Haywood County, NC Date: 2011-August-01Photographer: Gerald C Williamson
Nikon D7000
Tamron SP 90MM f/2.8 AF Macro
The stem of Prenanthes species are usually upright (except for P. bootii.) The stems of most species are glabrous in the lower part and most species may be hairy in the upper part. All Prenanthes species have nodding flower heads - the genus name comes from the Greek words for “drooping” (prenes) and flower (anthos). Prenanthes serpentaria may be 18 inches to over 6 feet tall.
Click on the photo for a larger image
Prenanthes serpentaria

Site: Blue Ridge Parkway, Haywood County, NC Date: 2011-August-01Photographer: Gerald C Williamson
Nikon D7000
Tamron SP 90MM f/2.8 AF Macro
The lower (proximal) leaves of Cankerweed are deeply lobed, as are those of several Prenanthes species. The lobes of Prenanthes serpentaria are usually more rounded than those of P. trifoliolata and P. altissima, although those of P. altissima may also be rounded. The petioles of each are winged.
Click on the photo for a larger image
Prenanthes serpentaria

Site: Blue Ridge Parkway, Haywood County, NC Date: 2011-August-01Photographer: Gerald C Williamson
Nikon D7000
Tamron SP 90MM f/2.8 AF Macro
The upper (distal) leaves of all three Prenanthes species discussed here are reduced in size and are usually unlobed.
Click on the photo for a larger image
Prenanthes serpentaria

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All content except USDA Plants Database map Copyright Gerald C. Williamson 2017
Photographs Copyright owned by the named photographer