Silphium pinnatifidum

Silphium pinnatifidum, the tansy rosinweed^[2] or cutleaf prairie dock, is a species of flowering plant in the family Asteraceae. It is native to the Southeastern United States where it is found in Alabama, Georgia, Kentucky, and Tennessee.^[3] Its habitat is prairies, barrens, and cedar glades.^[4]

Note the large phyllaries often indicative of Silphium

Silphium pinnatifidum
Conservation status
Vulnerable  (NatureServe)[1]
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Asterales
Family:	Asteraceae
Genus:	Silphium
Species:	S. pinnatifidum
Binomial name
Silphium pinnatifidum Elliott

Because of loss of its fire-dependent habitat, this species is uncommon and is considered vulnerable.^[1][5]

Although most populations are distinct, intermediate populations have been reported between Silphium pinnatifidum and Silphium terebinthinaceum, and some botanists consider S. pinnatifidum only a variety of S. terebinthinaceum. S. pinnatifidum was once thought to be a result of hybridization between Silphium terebinthinaceum and Silphium laciniatum, although molecular studies have indicated that S. pinnatifidum is too closely allied to S. terebinthinaceum for this to be the case.^[6]