Try bamboo sticks poking up in the planter - I had to do that to the catnip I have outside. The neighbor cats would jump in the pot and roll around before I stuck the sticks around in it. Now they only take bites out of the pieces hanging over the side of the pot! Or you could place chicken wire over the top of it. Then place whichever plant(s) you choose through the holes in the wire.
I hope you find a solution!!
