Silphium terebinthinaceum Jacquin. Prairie-dock. Phen: Jul-Sep. Hab: Mafic or calcareous glades, barrens, woodlands, prairies, and roadsides and powerline-rights-of-ways with remnant historical vegetation of those types. Dist: NY, ON, WI, and e. IA south to nw. GA, AL, MS, and AR (its distribution in s. OH, KY, TN, nw. GA, AL, and MS fragmented and disjunct); further disjunct eastward in the Piedmont of NC and n. SC.

Origin/Endemic status: Native

Taxonomy Comments: S. rumicifolium Small refers to plants of limestone in the Ridge and Valley province of e. TN and extreme sw. VA, alleged to differ from S. terebinthinaceum in the leaf bases cuneate at the base (vs. cordate or truncate), smaller leaf blades (only to 15 cm long), smaller plants (to 8 dm tall vs. to 30 dm tall), and outer phyllaries broader than long (vs. longer than broad). Var. lucybrauniae Steyermark, with leaf blades glabrous above vs. scabrous, and also alleged to have generally smaller leaves and stature may also warrant recognition (Steyermark 1951); if var. lucybrauniae is accepted, it should be spelled 'lucybrauniae' under provisions of the Shenzhen Code (Turland et al. 2018). S. terebinthinaceum (as still broadly treated after the removal of S. pinnatifidum) has a fragmented distribution, different habitats in disjunct portions of its distribution, and morphological variation suggestive that there is more than one taxon passing under that name. A rangewide study is needed.

Synonymy: = Mi, RAB, SE1, Tn, Va; = Silphium terebinthinaceum Jacq. var. terebinthinaceum – Ar, F, FNA21, K3, K4, NY; > Silphium rumicifolium Small – S, Perry (1937); < Silphium terebinthinaceum Jacq. – C, G; > Silphium terebinthinaceum Jacq. – S; > Silphium terebinthinaceum Jacq. var. luciae-brauniae Steyerm. – K1, orthographic variant; > Silphium terebinthinaceum Jacq. var. lucybrauniae Steyerm., correct spelling; > Silphium terebinthinaceum Jacq. var. lucy-brauniae Steyerm. – Il, Oh3, Steyermark (1951), orthographic variant; > Silphium terebinthinaceum Jacq. var. terebinthinaceum – Il, K1, Oh3, Perry (1937), Steyermark (1951)

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Wetland Indicator Status:

• Atlantic and Gulf Coastal Plain: FACU (taxonomic split from wetland indicator species)
• Eastern Mountains and Piedmont: FACU (taxonomic split from wetland indicator species)
• Midwest: FAC (taxonomic split from wetland indicator species)
• Northcentral & Northeast: FAC (taxonomic split from wetland indicator species)

Heliophily: 9