Western Rough Goldenrod
Solidago radula Nutt. is native to the open rocky places, dry woods, especially calcareous soils in the western part southeastern U.S. with infrequent, scattered populations further east. It is distinguished by its finely scabrous leaves that are either not 3-nerved or only weakly so (Semple & Cook 2006 FNA). It is highly variable in inflorescence shape and can be similar to S. nemoralis or S. velutina in general appearance. Leaf shape is similar to some plants of S. mollis to which it is likely closely related. Some plants from Texas with less hairy leaves have been treated as Solidago radula var. laeta (Greene) Fern and Solidago mollis Bartl. var. angustata Shinners. Shoots develop from either a short-branched caudex or elongated rhizomes. It can be similar to S. hintoniorum, native to northeastern Mexico.
In a multivariate study of S. subsect. Nemorales as then defined (Semple et al. 2018), specimens of S. radula were placed in the classificatory analysis into either S. radula or S. mollis with 1 specimen placed into S. californica. Tetraploids of S. radula were placed into S. mollis, which is polyploid. In the polygenomic study of Solidago (Semple et al. 2023), the single specimen of S. radula came out as sister to the S. velutina-S. altiplanities clade in subsect. Radulae.
The species includes diploids (2n=18) and tetraploids (2n=36). Semple (2023) mapped the cytogeography of S. radula.
Semple, J.C., K. Kornobis, and S. Bzovsky. 2018. A multivariate morphometric analysis of Solidago subsect. Nemorales (Asteraceae: Astereae). Phytoneuron 2018-42: 1–40.
Semple, J.C. 2023. The cytogeography of Solidago subsect. Radulae (Asteraceae: Astereae). Phytoneuron 2023-20: 1–12.
Semple, J.C., H. McMinn-Sauder, M. Stover, A.Lemmon, E. Lemmon, and J.B. Beck. 2023. Goldenrod herbariomics: Hybrid-sequence capture reveals the phylogeny of diploid Solidago. Amer. J. Bot. 110(7): e16164. https://doi.org/10.1002/ajb2.16164
Last revised 19 May 2025 by J.C. Semple
© 2025 J.C. Semple, including all photographs unless otherwise indicated
1-6. Solidago radula. 1. Habit, Semple & Chmielewski 6461, Erath Co., Texas. 2. Three dried shoots, Thomas et al 105653 WAT, Natchitoches Par., Louisiana. 3. Lower stem leaf, Semple & Suripto 9905 WAT, Carter Co., Missouri. 4-5. Lower mid stem leaves and leaf surface details, T et al. 105653. 6. Heads, Morton & Venn NA16258 TRT, Stone Co., Arkansas.