Surround plants with regular, spring loaded, mouse traps baited with peanut or almond butter... keep surface mulch fine so they don't have a nice warm hiding place above ground and plant within a moat of gravel.

Alternatively, keep ganja in containers with a couple of mouse traps and sit them in an area planted out with day lilies, irises or peonies.

Lastly, if you have cats and still have voles, I think you may be over feeding your cats.

Hope you can keep them of your remaining plants.

sara