Gopher Barriers Under Raised Beds
You recommend lining the bottom of raised bed veggie gardens with hardware cloth, but that degrades in a couple of years, and is a huge ordeal to replace.
So I am wondering whether 6″ or more of 3/4 or 1″ rock in the bottom of the bed would work against burrowing creatures like rabbits and gophers. My beds are 20″ high and I would add 14″ of compost and weed-free soil on top of the rocks.
Answer from Pat:
Gopher problems are severe this year. They are even showing up in large numbers in my garden where I’ve never before had an on-going problem. Cracked rock won’t keep them out. They are very good at moving it and getting through the rock to the plant roots and white grubs on the other side. A tile patio or reinforced concrete slab will keep out gophers, but then you would need to make much taller boxes and provide drainage out the bottom and sides. I suppose if you dug out the area where you are planning to put the boxes one foot deep with paths around 2 or 3 feet wide and then filled the whole area with a foot-deep layer of rock and put the boxes on top maybe it would keep them out, but I don’t know that for sure. I have seen gophers go through rock barriers often.
When I first came to California in 1945 the recommended barrier against rabbits, gophers, skunks, and rats was chicken wire or sometimes aviary wire to be nailed on the bottom of raised beds and also used for rabbit fences with the bottom of the fence buried in the ground. Later the recommendation changed to hardware cloth. You are the first gardener I have heard bring up the problem of degradation of the wire in the soil which will eventually happen, of course, but not in a couple of years as you fear. In all the years I have been advocating nailing wire on the bottom of raised beds so far no one has reported back to me that the wire rusted through and gophers were now invading, and I have been in this business of helping folks with their gardens for 35 years. Perhaps our population keeps moving but I have some friends who have lived and gardened in the same house for thirty years and the wire hasn’t stopped working for them. Also I have recommended using chicken wire under lawns to keep out gophers. The gophers will still get under the lawn but they can’t and don’t make mounds. One of my sons-in- law followed this advice about twenty years ago. He enjoyed a gopher-proof Santa Ana bermudagrass lawn for over ten years. He eventually sold that house but so far as I know to this day there are no gopher mounds on that lawn. (See the Quick Tip on page 358 of my book.) I suppose the type of soil one is dealing with might influence how long the wire lasts.
Bill Nelson of Pacific Tree Farms used to advocate putting sharp pieces of cracked glass in holes when he planted trees such as avocados even though he used chicken-wire baskets also as root-protecting barriers. I always felt that burying sharp glass was not a good practice due to the fact that it is cruel and also we cannot look centuries into the future and see how the land will be used then. It might become the location for a school or a family home with children or gardeners. So we would be leaving a cruel booby trap in the soil for a future generation. That sounds like bad Karma. I could see, however, laying down 2 layers of water-permeable, weed-preventing, landscape cloth with broken glass between them and leaving a record of exactly where this was so that it could be easily and safely removed in future. (Though I wouldn’t ever do this myself.)
If you want chicken wire or hardware cloth to last longer, the most logical idea would be to paint it with long-lasting rust preventative paint prior to installation. Since I know of wire lasting in the ground for twenty or thirty years, painted wire should last that much longer. Plastic-dipped fencing is also available, but I have no idea if it would last better underground than regular fencing or hardware cloth.