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.Flora of the Southern and Mid-Atlantic States Its habitat is prairies, barrens, and cedar glades. Because of loss of its fire-dependent habitat, this species is uncommon and is considered vulnerable.U.S. Forest Service
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. Jessee, L.H. and G. Yatskievych. 2011. A new putative hybrid in Silphium (Asteraceae: Heliantheae). Phytoneuron 2011–62: 1–7.
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