I’ve had several people write asking how to stop neighborhood cats from digging in their gardens and yards--a couple of them rather desperate for solutions. Other than installing a mile high fence (probably prohibited in your municipality anyway), calling animal control or worse, there are a few non-toxic, chemical-free tried and true solutions to this fairly common problem. Just remember that it may take a bit of trial and error along with persistence.
1. Rose Bush Clippings (with Thorns)
If you or a neighbor is pruning the rosebushes and they have an abundance of thorns, grab the clippings and scatter them on the ground where the cats are hanging out. Holly leaves probably work too or anything else with thorns.
2. Chicken Wire and Chopsticks
Maybe a strange combination, but some say it works. Lay the chicken wire on the ground and use the chopsticks as “spikes”.
3. Black Pepper
Buy a large container of black pepper and sprinkle liberally. Make sure you are not standing downwind however! Reapply as often as needed, but especially after a heavy rain.
4. Motion Sensor Sprinkler
Cats don’t like water. If you’re really aggravated or don’t want to invest in a sprinkler, try a water squirt gun.
5. Fresh, Non-Brewed Coffee Grinds
I have no idea why this would work, but many gardeners swear by coffee grounds liberally sprinkled around the garden.
Photo source: Catberry's Tails and Yarns