Access the branches of your mature trees in the yard with a ladder. Trim the branches so that the branches are shorter and not touching one another, if you happen to have multiple trees surrounding your home. Squirrels can easily get from one tree to another by climbing the branches and jumping from one to the next. The more that the branches are spaced apart, the more the squirrels will be deterred from jumping close to your home or garden.
Spray an all natural deterrent on your trees and plants. All natural deterrents can be purchased at pet stores, and are made out of bitter tasting ingredients that are safe for animals to ingest. The concept behind the deterrents is that animals can smell and taste the foul odor and flavor, so they are no longer interested in going in the direction of where the deterrent is sprayed. You can also make your own deterrent at home by combining water with hot sauce or red cayenne pepper and mixing it up in a spray bottle.
Place an animal statue near where you think the squirrels are accessing your yard or home. An animal statue, such as a plastic owl, will scare squirrels away because they will fear their natural predators. You can set multiple animal statues around the yard or on your roof to make sure that the squirrels are frightened away from a variety of angles.
Do not leave food outdoors. Food that is left outside will attract squirrels. If your yard is food-free, squirrels may have less of an interest in your area.