Wildflowers of the United States

Whorled Rosinweed, Three-leaved Rosinweed - Silphium trifoliatum

Genus Common Name: Rosinweed

Native Status: Native

Dicot Perennial Herb

Silphium trifoliatum - Whorled Rosinweed, Three-leaved Rosinweed. Silphium triofliatum is listed as a variety of S. asteriscus in Flora of North America, but ITIS continues to list it separately, although no longer with varieties, formerly var. trifoliatum and var. latifolium. Var. latifolium has opposite rather than whorled leaves. I expect that when all the updating is done, S. trifoliatum will be gone, and listed only as varieties of S. asteriscus.

Endangered in Illinois

Found in:
AL, DC, GA, IL, IN, KY, MD, NC, NY, OH, PA, SC, TN, VA, WV

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Distribution of Silphium trifoliatum in the United States and Canada:

Map courtesy of The Biota of North America Program.
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Site: Wilson County, TN Date: 2012-August-04	Photographer: Gerald C. Williamson Nikon D7000 Tamron AP AF 90MM Macro
Whorled Rosinweed has 8 to 13 yellow ray flowers. The ray flowers of Silphium develop the seeds; the disk flowers are sterile.

Site: Wilson County, TN Date: 2012-August-04	Photographer: Gerald C Williamson Nikon D7000 Tamron AP AF 90MM Macro
Whorled Rosinweed grows to about 6 feet tall and has leaves all the way to the inflorescence.
Click on the photo for a larger image
Site: Wilson County, TN Date: 2012-August-04	Photographer: Gerald C Williamson Nikon D7000 Tamron AP AF 90MM Macro
The smooth, usually glaucous stem of Silphium trifoliatum has mostly whorls of 3 leaves - occasionally opposite or rarely a whorl of 4 - which are nearly sessile (very short petioles) and narrowly ovate. The leaves have very shallow teeth or may be entire. Silphium brachiatum is similar, but with opposite lanceolate leaves having cordate or truncate bases, and fewer ray flowers. The distribution of S. brachiatum is also much smaller, being limited to a few counties in Alabama, Georgia, and Tennessee.
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References used for identification and information:

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Silphium trifoliatum initially published on USWildflowers.com 2012-08-06; Updated 2017-03-02

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All content except USDA Plants Database map Copyright Gerald C. Williamson 2024
Photographs Copyright owned by the named photographer

Code Update 20230302