Cat Grass Organic Cat Hairball Treatment Organic and loaded with all the fiber your pet needs for healthy digestion, our cat grass kit provides hairball control for cats as well as a tasty treat. 1. Sow your seeds. Sow cat grass seeds directly into your soil (for growing indoors or outdoors), about a quarter-inch deep. If you are planting in rows, ensure they are one inch apart. Cat grass can grow indoors all year round, but should only be planted outside during spring, after the threat of frost has passed. 2. Germinate. For indoor growing, keep your soil moist. Partially cover your planting pot in plastic wrap and place in a warm and dark place. After two to three days, your cat grass seedlings should start sprouting. 3. Provide direct sunlight. Cat grass will need plenty of sunlight while it’s growing. Make sure your cat grass receives direct sun outdoors, and if growing indoors, place near a windowsill that can also provide full sun. 4. Firm the soil. Firm the soil lightly and keep it evenly moist. Be careful not to overwater, as it can ruin the roots.