You can put the the mothballs(you do NOT want them directly in the dirt) in something with holes in the top. I used yogurt and margarine containers. It smells hideous so my dogs avoided the area too. I used this method to deter stray cats. PJ

PJ what a great idea. I've been trying to figure out an easy way to keep the stray cats from hiding around my bird feeders and birdbaths. Do you know if the mothballs bother birds? Wouldn't want to drive them away from their cafeteria and swimming pool!

oh boy that sounds to good to be true. I will also try this IF like debndal said will not keep the birds away. Since I love watching them. They get real loud when I forget to feed them. That is one time when the Cardinals do not fly away when I get closer then they usually let me. Until I feed them and then they are back to there normal distance keeping.

Great idea with the mothballs! They will need to be replenished occasionally. I have had luck with putting dog fur in the toes of nylon stockings and attaching the "fur balls" to plants. Since you have dogs, getting the fur might not be a problem. This also needs to be renewed, especially after a heavy rain.
The digging problem can be solved with chicken wire placed about 2" under the surface. Make X cuts when you plant, and replace the wire. The stems and fronds will come up through the wire, and the squirrels will be deterred from digging.
According to the Birder's Handbook, passerines (which are the majority of birds you see at feeders) and woodpeckers do not have a highly developed sense of smell so the scent of mothballs probably would not deter them from visiting feeders and watering stations. Vultures, on the other hand, probably do have a highly developed sense of smell, and also very strong stomachs!

I've found the squirels cause less trouble if fed.

They can really be a nightmare though. Very hard to get rid of.

give the squirrels something else to eat. I've never seen them eat caladiums and I plant loads of them every year. Haven't seen them eat hostas either. I have watched them delight in tender rose buds and the the sweet shoots from a hibiscus. I usually have plenty to share.

You can sprinkle some ammonia on an old sock (brown blends in with mulch) and that will deter squirrels without being a hazard to plants and pets.

Here is a link that might be useful: Mothball poisoning

give litte,
I know a bit about birds. They have a poor sense of smell. They also have a poor sense of taste. For example very hot chilies don't affect them.I do not think moth balls would work on birds.
Bird deterents are usually visual/auditory. The most effective and clever(somewhat annoying) bird deterent is at my local farmer's market. They have a recording of a hawk's nest (screech screech) in the rafters of the outdoor market. Birds avoid that area entirely. PJ

oh then I will not geth that hawk's nest because I would not wanna miss out on the beautiful singing of my cardinals and other kinds. Thanks PJ

Don't eat mothballs or use them to fumigate your home! That is stupid. Outside they won't have the same effect as being in a house. PJ