squirrels: 1, potted plants: 0

I've got several planters on my front porch and the back deck which seem to have caught the attention of the local squirrel population. I think at least one of them is trying to dig a hole to China via my planters, based on the depth of the holes I keep finding, and my hostas are not terribly happy about this. I've already lost one pot of petunias and it looks like it took somewhat less than 18 hours for them to find the new container of portulaca and dig up one of the smaller plants. Any ideas for non-lethal (and preferably non-toxic) ways to discourage them from digging up my planters? Poison's not an option; I like the little critters and they're not doing any serious harm, I'd just like them to go dig pretty much anywhere else. I was going to try adding spaghnum moss to cover the soil in the planters containing the hostas and see if that distracted them, but that won't work very well with the portulaca or the petunias. Does sprinkling red pepper around the plants work? If all else fails, there's chicken wire I suppose.