but I still had two to four hostas damaged by voles.

==>>> how does that compare to previous years???

Ken, last year I only had one that I believe was damaged by voles. Before that, I didn't have so many hostas. I've lost several through the years but I don't know if those losses were due to voles or not.

I believe voles may have gotten into a couple of oak leaf hydrangeas in recent years.

By probing with my fingers around the damaged hostas, I found clear evidence of tunnels around two of them. The other two seem to be in solid ground -- their damage could be from a couple of unusual freezes we've had.

Does "regular" castor oil have a noticeable odor? The castor oil I purchased does not.