I lined the bottoms of my raised beds with wire and they have worked fabulously for 2 years now--- no issues at all, though I can't really comment on the chemical issues.

I would think voles could eat through hardware cloth. I don't know if gravel would be helpful. Perhaps if it was large stone gravel. I have read of lining beds with chicken wire along the bottom, and up the sides to prevent tunneling varmints. You'd want to place the wire lower than the plants will develop their roots. That will be a lot of work!

Lorna

I think I've finally figured out why I've never had any bulbs flower after reading this thread! VOLES! I've seen them in my perennial beds--and my terriers occasionally snack on them when they can find them--but it's obvious those little suckers are busy, because I've tried planting dahlias, ixia and a shade foliage bulb that I can't remember the name of at the moment. NONE of them has ever even broken the ground! I thought I was doing something wrong but now I know the culprit.

I like the tip on crushed oyster shell; I keep it on hand for my chickens, and it sounds a lot easier than embedding hardware cloth.

Hardware cloth is a welded galvanized, stainless steel, and PVC covered wire available in meshes of 1/8 inch, 1/4 inch, and 1/2 inch and probably others as well, and it can be a very expensive means of control. Buried in soil it may be effective for a number of years, I have some that is still in very good condition after 20 years but that has been above ground all this time, but even galvanized wire will rust out in consistently moist conditions after some time. Hardware cloth is a very effective method of stopping voles from getting to plants you do not want them to eat but can be quite expensive, initially.

Yes, Kimmsr is right...hardware cloth is very expensive, and there's no way voles could eat through it. It covers the windows to my chicken coop, and not even raccoons or coyotes can get through those windows of hardware cloth. I don't use the PVC covered kind (haven't ever seen that) just the plain old galvanized stuff.

I have used juciy fruit gum to get rid of voles. stick it into the opening of their holes. they eat it and it kills them and they turn into fertilizer

This gum thing is another myth that hangs around forever. Research has indicated that if the voles, moles, or whatever, actually will eat the gum (it smells nothing like what they normally eat) their digestive system will process it just as well as yours will digest gum. Gum will not do much of anything to control these pests.
Because these voles, moles, and other types of critters just have a long ago evolved habit of moving on periodically for no apparent reason people that do use these useless controls think they do work, when they have no affect on the target critter.

Thanks to all who replied. I appreciate your ideas.
Elke, where do you buy your crushed oyster shells? They sound like a great addition to my anti-vole arsenal.

Because I have to buy them for my chickens, I can tell you that you can find them at any farm supply/feed store. They are ridiculously cheap (I pay $2.00 for 4 pounds).

Arwmommy, yours are much cheaper than mine! My TSC charges $6 for 3 lbs.!

I wonder if crushed oyster shell would work for slugs, sprinkled around the base of the plant? I've heard of this for DE (which I also have on hand) but am wondering if the oyster shell might work better since it wouldn't blow away/absorb as easily?

cornucopia (and others) --
you can get crushed oyster shell at any feed store or pet store that carries supplies for domestic fowl or pet birds, who use it as a digestive. gardener's supply co. was selling pricey little bags of this as "bulb insurance" or some such, but, inspired to search on "crushed oyster shell," i got lots of web hits from pet shops. i called the place where i buy dog food -- and scored.

arwmommy and farfaraway -- you are being ROBBED!!! ROBBED i tell you. i get my shell $7.99 for a 40 pound bag, which often lasts me two seasons. and hardware cloth really isn't "very expensive." you have to order full rolls since it is most often sold in short lengths. my local hardware store ordered me a 50' roll, 3' tall, 1/2 inch mesh for just under $70. since it has a lifespan of about 20 years, i don't consider that out of line.