Hi Karen, welcome to the forum! Unless your peony is to be dug anyway, like to divide, I would just gently tug the aster roots out. Wet the soil down well the eve before so they're easier to get out. Even that might disrupt the tiny feeder roots if you have to remove a lot of aster roots so watch the peony after and shade it if it appears to droop more than normal, just for a few weeks. Good luck!
