Also check your local law on pet ownership. In my town there is of course no leash law for cats, HOWEVER owners are required to keep them on their property. They roam around free most everywhere, but if one were to cause a problem the owner can be blown in.As some have suggested pepper flakes/powders do you. You can also sprinkle some moth balls in the area where the plants are. No Dog or Cat will get near those.
Before you consider some of the more violent methods check you State and Local Animal Cruelty laws/regulations.
Here in Texas it is a felony to inhumanely kill an animal ie .22,air rifle etc. Trapping and dumping to a "new" location, where they do not know the food sources and dangers can also be in violation of Loco's Law here in Texas.
So unless you are prepared for a criminal conviction on your record, which will invalidate any concealed carry permit you have....I would use pepper and or moth balls.
Also remember cameras can also be used against you in animal cruelty.
Unless law has changed you do have a right to defend your livestock/agriculture from harm (can't think of the exact wording but it's not harm). Have had issues with dogs going after cattle and pigs before......
Mothballs work for lots of critters. Is there any worry about the ammonia leaching into your garden soil?