Silphium radula var. radula
(Rough Rosinweed)
Silphium radula var. gracile, Along FM2434 west of Columbus, Colorado Co. 6997
Silphium radula var. gracile, Along FM2434 west of Columbus, Colorado Co. 7004
Silphium radula var. gracile, Along FM2434 west of Columbus, Colorado Co. 6999
| Scientific Name | Silphium radula var. radula (Silphium simpsonii var. wrightii, Silphium reverchonii) | USDA PLANTS Symbol | SIRE4 |
| Common Name | Rough Rosinweed, Simpson's Rosinweed, Reverchon's Rosinweed | ITIS Taxonomic Serial No. | 780957 |
| Family | Asteraceae (Sunflower) | Flora of North America Ref. | Click Here |
| Description | Habitat: Sandy, gravelly or limey soils in open areas, prairies, woodland openings, fencerows and roadsides. Plant: Erect perennial 12 to 36+ inches tall, one or a few stout, bristly-hairy, reddish-brown stems, somewhat branched in upper portion. Leaves: Lanceolate to ovate; 1 to 8-1/2 inches long and 1/4 to 3-1/8 inches wide, entire or dentate margins; lower stem leaves opposite and petiolate, upper leaves are much smaller, alternate or opposite and petiolate or sessile; surfaces are rough and may have bristly hairs. Inflorescence: Usually solitary, large, bright yellow composite flowers; up to 3 inches across, 20 or more rays and many (100 to 175) yellow disk florets; involucre with rough, wide, overlapping phyllaries with pubescent hairs, spreading to slightly recurved with pointed tips. Bloom Period: April to September. References: S. radula in "Wildflowers of Texas" by Michael Eason, S. radula var. radula in Flora of North America, S. simpsonii var wrightii in "Manual of the Vascular Plants of Texas" by Correll and Johnston and "Wildflowers of the Texas Hill Country" by Marshall Enquist; S. gracile in "Wildflowers of Texas" by Geyata Ajilsvsgi; and "New Combinations in Silphium" by Jennifer A. Clevinger. Note: The taxonomy of the Silphium genus is confusing, with conflicting names and synonyms. The names and associated descriptions here represent what is believed to be correct as of now (2024). |
BONAP Distribution Map Map Color Key |
Texas Status: Native |
Banner photo of Castilleja indivisa and Lupinus ssp. taken along FM 1323 north of Johnson City, Blanco County
© Tom Lebsack 2024