like the plant lol. on the cheap, just put some cinnamon sticks in the there. or citrusy stuff.
Cats are not keen on the smell of citrus either. So you could try using orange or lemon peel in your yard as a deterrent. Similarly some folks advocate coffee grounds, blood meal, cayenne pepper, lavender oil, lemon grass oil, citronella oil, peppermint oil and eucalyptus oil.
easiest thing to do is just kick the goddamn thing...i hate cats