There has been lots of discussion lately on herbicides useful for peonies. Check with Cooperative Extension, especially Phil Kaspari and Steve Seefeldt for a list of herbicides that are registered for use on peonies in Alaska. This article was written in 1994 and included herbicide treatments of ‘Sarah Bernhardt’ peonies. The authors found no toxicities or growth changes on peonies following applicaiton of Pennant, Derby, Stakeout, Gallery, Snapshot, Dacthal, and Pre-M. Check the article for rates and application times. This study was conducted in North Carolina.

Skroch, W.A., C.J. Catanzaro, A.A. De Hertogh and L.B. Gallitano. 1994. Journal of Environmental Horticulture. 12(2)80-82.