Like dianew said cats hate citrus, so lemon or orange rinds could scare them off.
I use lemon polish to keep them off furniture so it may work using rinds in a garden. or put juice all round the top of your fencing so just associate your garden with that so will keep away.
I can understand your frustration, and I'm sure the cat was fine, they can withstand something like that, but it's not soemthing I would recomend on a regular basis.
Also, for my cats anyway, they are more active in summer, then tend to stay in more in winter, so you may find there cool it off in winter months, but sure that wont help the plants!