My apartment complex has a stray — an adorable little black cat who I often see out on my patio. A few weeks ago I figured out why. He has been using my planters as a litter box.
Now they sell all kinds of crazy things to keep the strays at bay, but I’m not really interested in anything that requires huge warning labels about how to handle it. I want the kitty to find a new potty, not be traumatized or blinded or harmed in any way. So I left those at the store and instead bought two six-packs of annual flowers (lobelia, to be specific). I cleaned out the deposited cat-goodies, replaced the top level of soil, planted, mulched and voila! Not a single cat-scratch since then, plus the plants that lived there are already looking much healthier.
Of course the kitty moved on to two other planters that I missed, but at least now I know how to handle the problem.