Canadian Brand. For those with a green thumb, here is a complete kit to grow healthy indoor cat grass. The kit contains primed oat and barley seeds, growing medium, full instructions and a sample of catnip herb. Using the product container simply mix the seeds into the growing medium and add a small amount of water. Place the container in warmth and full sunlight. Seeds will begin to sprout within a few days, and will produce long blades of cat grass for kitty to nibble and enjoy. Cat grass is important during the winter months for indoor cats, and can help with digestion.