Silphium pinnatifidum, the tansy rosinweed 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.[1] Its habitat is prairies, barrens, and cedar glades.[2] Because of loss of its fire-dependent habitat, this species is uncommon and is considered vulnerable.[3]
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.[4]