Hi Ann,
Squirrels are like rodents, they love to dig the soil or simply cut the plants to eat/chew some plant parts.
If you can afford to establish your greenhouse, this is the most effective way to control squirrel and other pests attack. However, if you've no budget for constructing a greenhouse, the best way is to fence your garden around and put about 1 meter plain galvanizeiron from the base around your fence. Squirrels or rodents can't enter inside the fence anymore.
Note: Dig the galvanize iron about 6 inches below the soil around the fence to avoid the squirrel/rodents from digging to enter inside the fence.
I hope this solves your problem! For further information about home gardening tips and resources, please send request at:cris@ramasasa.com.
Happy gardening!
cris
www.crisramasasa.com