of course let me give you a word to the wise.. If your gonna keep a cat around to do these things for you, put him a litter box out there.. other wise cats will be cats and do their business where they can. INCLUDING GROW BEDS.
LOL..
But... given the choice, they will always choose the litter box over some wet grow bed.

yet another symbiotic part of the system.... :)

in fact put a litter box in there even if its not your cat that keeps coming round... if there are mice and the neighbors have cats, your gonna have a constant visitor.. rather than run him off and fight it, just put a litter box in there and let the cat become part of your system..