How can you stop getting weeds from the garden next door?

Repellent plants are practical if they will grow in your area. You can also put up a fence, even a low, decorative one, and run a low-voltage hot wire around the top. You can get a pet-voltage box that will not injure an animal, and the wire itself, at pretty much any hardware store. After getting shocked a few times the cats will probably stop trying to get in altogether. However, this method is not advised.

Try a concoction of 'hot pepper' spray. This can be made by heating Red Pepper Flakes in a pot of hot water, or mineral spirits. Spray this liberally around the intended area and all animals should avoid it. Many commercially available solutions are designed specifically to 'repel' deer, rodents, and cats.

Another sneaky method is to grow some Catnip, or Cat grass nearby, but far enough away to keep the felines busy and hopefully forget about your target plants. One of the reasons cats (& dogs) frequent a bed is to spray/urinate OVER a previous animals scent. Keep that in mind.

Cat Stop is an ultrasonic, battery-operated cat repellent with a motion detector. See the SafePetProducts web site to read more about this highly recommended product.

Push wooden chopsticks or 10-inch plant stakes into flowerbeds every eight inches to discourage digging and scratching.

Cats dislike citrus smells. Scatter orange and lemon peels or spray with citrus-scented spray. You can also scatter citrus-scented pet bedding such as Citrafresh.

Coffee grounds and pipe tobacco also work to repel cats. Some people have also suggested lavender oil, lemon grass oil, citronella oil, eucalyptus oil and mustard oil.

you can also put pine cones around your plants, cats hate to step on them

I find a Jack Russell terrier ideal.