Motion detection sprinklers and sharp objects planted sparingly throughout the garden help ward off cats. Cats dislike the smell of vinegar, citrus fruits, human hair, rue, lavender, rosemary and lemon thyme, so using these in the garden will deter cats as well.
Motion detection sprinklers, available at most local hardware stores, will spray when they detect motion. Since most cats hate water, after a few sprays from the sprinkler, cats will steer clear of the source of the water. Pine cones, forks, pebbles and wooden chopsticks deter cats from scratching and digging in the garden.
Human hair wards off cats, so clean out the hairbrush and place the hair around the garden to keep the area cat free. Cats do not like the smell of citrus. To deter cats from the garden, sprinkle citrus peels around the area and around the plants.
Planting certain plants that cats despise in the garden will deter cats from the area. Rosemary, rue and lavender emit odors that cats find offensive causing them to steer clear of the source of the smell.
If all else fails, try attracting the cats to another area of the yard, as opposed to running them out of the garden. Things like a litter box, cat food and catnip will welcome cats to other more inviting areas of the yard, keeping them out of the garden area.