''Silphium pinnatifidum'', the tansy rosinweed or cutleaf prairie dock, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

in the family

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

. It is native to the

Southeastern United States The Southeastern United States, also referred to as the American Southeast or simply the Southeast, is a geographical region of the United States. It is located broadly on the eastern portion of the southern United States and the southern por ...

where it is found in Alabama, Georgia, Kentucky, and Tennessee. Its habitat is

prairies Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the ...

, barrens, and

cedar glades A calcareous glade is a type of ecological community (ecology), community that is found in the central Eastern United States. Calcareous glade (geography), glades occur where bedrock such as limestone occurs near or at the surface, and have very ...

Because of loss of its fire-dependent habitat, this species is uncommon and is considered vulnerable. Although most populations are distinct, intermediate populations have been reported between ''Silphium pinnatifidum'' and ''

Silphium terebinthinaceum ''Silphium terebinthinaceum'' is a member of the Asteraceae, a family that includes Helianthus, sunflowers, and is commonly referred to as prairie dock or prairie rosinweed. It is native to central and eastern North America. "Rosinweed" became on ...

'', 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 ''Silphium laciniatum'' is a species of flowering plant in the family Asteraceae known commonly as compassplant or compass plant. It is native to North America, where it occurs in Ontario in Canada and the eastern and central United States as fa ...

'', 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.

References

{{Taxonbar, from=Q16992572 Silphium (genus), pinnatifidum