Vascular Plants of North Carolina
Account for Prairie Dock - Silphium terebinthinaceum   Jacquin
Members of Asteraceae:
Members of Silphium with account distribution info or public map:
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Section 6 » Order Asterales » Family Asteraceae
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DistributionPiedmont only; the broad gap apparently is real and not an artifact. Newly discovered in Anson County by Becky Dill in 2022.

Western NY to Ont., WI, and NE, south to northwestern GA and AR; disjunct to NC and SC. The only VA county known so far is Lee, in the far southwest; it has yet to be found in the southern Piedmont of VA.
AbundanceRare over its eastern and central Piedmont range, but can be locally quite common (1,000 or more plants) at a few sites in Granville and Durham counties -- in the Durham Diabase Sill area. Populations in the southern Piedmont are struggling against development, except the Anson County pop (40 flowering plants) discovered in 2022 which is on a remote roadside. This is a Significantly Rare species.
HabitatGlades, barrens, prairie-like areas, oak-hickory-juniper woodlands, openings, roadsides -- in NC always on high pH soils, mostly on mafic substrates. A characteristic NC "prairie-plant" species.
PhenologyFlowering and fruiting July-September.
IdentificationPrairie Dock looks superficially like some of our rosinweeds (Silphium spp.) in its naked stem towering over sizable basal leaves. However, its leaves are larger (up to 1.5 feet long), without any lobes, coarsely toothed, cordate at the base, and usually stand erect. The heads are showier, due to long rays. This is one of the most spectacular of the "prairie-plant" species in the state, whose main range lies in the Midwest. With its stems often reaching 6-8 feet tall, when in bloom a large population is quite stunning. Even just the basal leaves are identifiable, though take care in ruling out other composite genera such as Parthenium spp., which do not have leaves with cordate bases.
Taxonomic CommentsNone. The word "terebinthinaceum" means "of or pertaining to turpentine", in reference to the plant's resin-like sap.

Other Common Name(s)Prairie Rosinweed
State RankS2
Global RankG4G5
State StatusSR-P
US Status
USACE-agcpFACU link
USACE-empFACU link
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Becky Dill2 Sept 2022, Pleasant Grove Church Road. AnsonPhoto_natural
B.A. SorrieGranville County, same data. GranvillePhoto_natural
B.A. SorrieGranville County, 2007, Picture Creek Diabase Barrens. GranvillePhoto_natural
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