As far as I can tell they do, but I'm sure to be proven wrong eventually. I had a couple of raspberry bushes I'd gather from every few days and I made the mistake of hitting one. Didn't destroy, so I left it alone and came back a few days later - it was still there and still growing berries. Walls will keep stuff out, but fences won't do much for you other than restrict foot traffic. The spike log wall looking thing is the way you want to go if you want to build fences. They function as good as house walls for keeping rocks, poison clouds, and so forth out.