This can be difficult. Outdoor animal repellents are available at nurseries. These can be applied around the outside of the garden and may help.
Cats are very attracted to newly disturbed bare soil. They are often most likely to use the garden when you are doing bed preparation and soon after planting. Do not leave turned soil bare. Immediately cover it with a few inches of pine straw. Pine straw is often used as a mulch when cats are an issue. They are less likely to use an area mulched with pine straw.
Don’t forget to remove any feces and even a spot of soil soaked with urine. Removing this helps remove the smell that attracts cats to use the area to do their business.
Finally, there are motion activated sprinklers. They come on and spray water anytime they detect movement in an area. Hitting a cat with a jet of water is a great way to discourage them from going into your vegetable garden. You can order these online. Just do an Internet search for – motion activated sprinklers.
Consumer Horticulture Specialist
The LSU AgCenter and the LSU College of Agriculture