Silphium pinnatifidum

{{short description|Species of plant}}

{{Speciesbox

| image = Silphium pinnatifidum leaves.jpg

| status = G3

| status_system = TNC

| status_ref = {{Cite web

| publisher =NatureServe

| title = Silphium pinnatifidum

| url = http://www.natureserve.org/explorer/servlet/NatureServe?searchName=Silphium+pinnatifidum+

| accessdate = 2014-05-04}}

| genus = Silphium

| species = pinnatifidum

| authority = Elliott

}}

Silphium pinnatifidum, the tansy rosinweed{{PLANTS|id=SIPI2|taxon=Silphium pinnatifidum|accessdate=15 November 2015}} 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.[http://www.herbarium.unc.edu/flora.htm Flora of the Southern and Mid-Atlantic States] Its habitat is prairies, barrens, and cedar glades.{{cite book |last=Chester |first=Edward |date=2015 |title=Guide to the Vascular Plants of Tennessee}}

File:Silphium pinnatifidum phyllaries.jpg Because of loss of its fire-dependent habitat, this species is uncommon and is considered vulnerable.[https://www.fs.fed.us/wildflowers/plant-of-the-week/silphium_pinnatifidum.shtml 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.[http://www.phytoneuron.net/PhytoN-Silphiumhybrid.pdf] Jessee, L.H. and G. Yatskievych. 2011. A new putative hybrid in Silphium (Asteraceae: Heliantheae). Phytoneuron 2011–62: 1–7.