Flora of the Southeastern United States

Silphium terebinthinaceum Jacquin. Common name: Prairie-dock. Phenology: Jul-Sep. Habitat: Mafic or calcareous glades, barrens, woodlands, prairies, and roadsides and powerline-rights-of-ways with remnant historical vegetation of those types. Distribution: New York, Ontario, Wisconsin, and e. Iowa south to nw. Georgia, Alabama, Mississippi, and Arkansas (its distribution in s. Ohio, Kentucky, Tennessee, nw. Georgia, Alabama, and Mississippi fragmented and disjunct); further disjunct eastward in the Piedmont of North Carolina and n. South Carolina.

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, POWO, RAB, SE1, Tn, Va; = Silphium terebinthinaceum Jacquin var. terebinthinaceum — Ar, Can, F, FNA21, K4, NY; > Silphium rumicifolium Small — S, Perry (1937); < Silphium terebinthinaceum Jacquin — C, G; > Silphium terebinthinaceum Jacquin — S; > Silphium terebinthinaceum Jacquin var. luciae-brauniae Steyermark — K1, orthographic variant; > Silphium terebinthinaceum Jacquin var. lucybrauniae Steyermark, correct spelling; > Silphium terebinthinaceum Jacquin var. lucy-brauniae Steyermark — Il, NS, Oh3, Steyermark (1951), orthographic variant; > Silphium terebinthinaceum Jacquin var. terebinthinaceum — Il, K1, NS, Oh3, Perry (1937), Steyermark (1951). Basionym: Silphium terebinthinaceum Jacquin 1770

Links to other floras: = Silphium terebinthinaceum var. terebinthinaceum - FNA21

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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