Some say when the earth comes to an end rats will be the sole survivors. My money is on voles.

Voles are underground terrorists and my garden’s Public Enemy No.1. They may look like cute, plump mice but these rodents are the spawn of the Devil and guilty of outrageously bad behavior.

After burrowing under ground they are active day and night eating plants, bulbs, roots of trees and shrubs —most everything really, they aren’t picky. Laburnum, styrax, edgeworthia, roses, camellias, azaleas, lespedezas, astilbes (Big-Mac for voles), epimedium, daylilies, woodland orchids, and even toxic hellebores and foxgloves have been ravished and killed. I could go on and on. Nothing is safe.

Female voles as young as 4-6 weeks can mate throughout the year—-that is, when they aren’t eating. Once pregnant, gestation is only about three weeks, and each litter can have 3-6 young. (One reference said up to 10 young). Do the math: With that sort of reproductive ability they can, in a very short time, overrun a planet, much less a garden. Pretty darn horrifying.

What’s an organic gardener to do?

While I harbor murderous intent, poisons and traps that also endanger beneficial wildlife (not to mention beneficial family members) are out of the question.

We have had some success with Sonic Molechasers that repel voles and other borrowing rodents with penetrating underground sonic sound at 15 second intervals. (Despite the name, moles are not my problem; they eat slugs, not plants, though voles are opportunists and will take over the moles’ sub-soil tunnels). But Molechasers are powered by batteries and therefore useless in winter when batteries run out and can’t be replaced. I was heartbroken one Spring — when the snow finally melted— to find several beloved camellia plants, loaded with buds, lying on the ground rootless and dead.

What’s an organic gardener to do?

Well, I found a natural solution that works: VoleBloc, a non-toxic soil additive consisting of coarse particles of slate,  protects plants because voles have sensitive skin and avoid tunneling through abrasive material.

So far so good. Here it is April and my camellias are still rooted and happy. Ditto for all the plants treated with the repellent. (Note: while this winter was unusually snow free, for purposes of an accurate test I did not replace any of the Sonic Molechasers’ dead batteries. VoleBloc was on its own).

Protecting plants from predator damage is never ending. Experience tells me that nothing is foolproof at all times and in all circumstances. So with that caveat, I’m happy to say that VoleBloc is working now. I’ll keep you advised.

Addendum April, 2013: I can no longer recommend VoleBloc. Not only has it become prohibitively expensive, but the voles ate the roots of two VoleBloc treated plants this past winter. I’m now trying something new. More about that soon.

August 20, 2013: I now highly recommend 3/8 Burgundy Red chip, sharp particles of stone that reliably protects plants against voles, at less than a quarter of the cost of Volebloc. I purchased the stone at Southampton Masonry in Southampton N.Y., (631) 259-8200.

2015: The Burgundy Red chip stone still works. For maximum protection, place the plant on top of a layer of stone in the planting hole, mix some stone with the planting soil, and then, after planting, place a layer around the plant.