Hi Joanne, I like the idea of the bottle in the ground, but I've noticed I still have a vole problem unfortunately where there's a few wine bottles half buried. In all fairness, in my round bed where I have a vole issue, I also have string wrapped around the bottle in the center of the bed which stretches out to the edge of the bed to create radial spokes and dividers for the different plants growing there. Maybe the string is enough to dampen the vibration and make it ineffective for controlling voles.
Do you or anyone else have experience with the sonar sticks that are to be deterrents for voles? I'm concerned to set traps above as I have an 18 year old dog that still gets into what she shouldn't. I hate that I can't plant from seed without having my winnings absconded!