Squirrels can jump standard stockade fences, but chicken wire can keep them out of your garden and yard. Include the top when boxing.
Motion-activated sprinklers like Orbit's Yard Enforcer connect to a garden hose and offer adjustable coverage areas
Dogs annoy squirrels. If you have one, it's probably warding off furry pests. If not, add scarecrows.
Make a hot-pepper spray to use around trees and other squirrel entryways. It's safe for plants and squirrels avoid it.
Squirrels use bird feeders as buffets. To keep squirrels out of your yard, remove the bird feeders.
Squirrels dislike peppermint, so plant it around your property. Mint grows fast. If you're worried about invasiveness, use pots.