We use them for the kittens because of their eyes being so suseptable to injury. They are polydacyl so they aren't able to retract those extra claws.

We get them at a local vet's office for $19.00 a box. 40 Nail caps come in a box, so they last quite a while.

Some people don't like them because they do fall off...thus requiring more effort and time. (I hear this ALL the time at work.) But it really isn't too hard or time consuming to apply them, especially just to one cat.

As far as the kitty using the planter vs. the litter box. The only way I know to avoid that is to get rid of the plants. We only have 1 small plant in our apartment and its high up and away from their reach. Maybe someone else will have better advice.