About Silphium pinnatifidum T.Nees
Silphium pinnatifidum, commonly known as tansy rosinweed or cutleaf prairie dock, is a flowering plant species belonging to the Asteraceae family. It is native to the Southeastern United States, where it occurs in Alabama, Georgia, Kentucky, and Tennessee. Its natural habitats are prairies, barrens, and cedar glades. Due to the loss of its fire-dependent habitat, this species is uncommon and classified as vulnerable. While most populations are distinct, intermediate populations have been documented between Silphium pinnatifidum and Silphium terebinthinaceum, leading some botanists to treat S. pinnatifidum as only a variety of S. terebinthinaceum. S. pinnatifidum was once hypothesized to be a hybrid of Silphium terebinthinaceum and Silphium laciniatum, but molecular studies have shown that S. pinnatifidum is too closely related to S. terebinthinaceum for this hypothesis to be correct.
