Silphium compositum Michx. var. compositum

Locations ofSilphium compositum Michx. var. compositum in Virginia

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Botanical Name
Silphium compositum Michx. var. compositum
Common Name
Carolina Rosin Weed
Silphium compositum Michx. (sensu stricto)
Flora of Virginia Name/Status
Silphium compositum Michx. var compositum
Two well-marked members of the Silphium compositum group occur in Virginia. Flora of the Southeastern U.S. (Weakley et al. 2023) treats them as species (see Synonyms), but most other sources consider them varieties or lump them entirely (e.g., FNA). Silphium compositum var. compositum represents Virginia plants in the se. Coastal Plain and outer s. Piedmont with lobed leaves. Its in-state distribution only slightly overlaps that of the unlobed var. reniforme. The lobing on leaves of var. compositum is highly variable, and occasional plants with sparse and shallow lobing appear to approach var. reniforme. For the time being, we are following the traditional varietal treatment pending future phylogenetic studies that can definitively clarify the appropriate rank for these taxa.
Mesic to dry woodlands, clearings, meadows, and road banks. This is the more numerous of the two vars. in Virginia, and is frequent in the inner s. Coastal Plain and outer s. Piedmont.
Native Status

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