I am so gald I came across this thread, I've been having vole problems for a while now. I had to rip out ALL my ground covers the other day since they provide ideal cover and nest material. Most of the perennial were saveable, but they almost took out a Sumac and a full grown Clematis
I plan on hitting WM soon since they always have their Daffs on for super cheap end of season, I will also try the Euphorbia! I have one and now that I think of it, its one of the few plants that was untouched! They also seem to have a dislike for Yarrow, the Tulips planted under the yarrow are the only ones that have been untouched.......