Go to a natural foods store, or anywhere you can buy in bulk, and buy some wheat berries, thats unground wheat. Get a pot with some potting soil sow the wheat( just like the old days) and water. When the wheat sprout and get a couple inches tall let the cats at it they'll leave all the rest of your plants alone. Wheat is cheap you only need a n ounce or two to grow a boat load of kitty grass.