While catnip is unlikely to seriously harm your cat, in large quantities it has been known to cause vomiting and diarrhea and can overstimulate your cat’s central nervous system to the point that it could harm itself. So be careful to grow in a cat-proof area. Catnip belongs to the same family as mint (Lamiaceae) and is part of the Nepeta genus. The true catnip plant is Nepeta cataria. There are other Nepata species, but none seem to have the same near-magical appeal to cats.
How to Grow Catnip Indoors
Sunlight
Catnip is not particularly picky about outdoor sunlight, but indoors it must receive as much direct sunlight as possible, up to five hours a day of strong sunlight on a bright windowsill. Too little sunlight produces leggy and spindly growth.
Temperature and Humidity
Catnip grows best at temperatures between 55 and 85 degrees Fahrenheit and tends to perform poorly in hot, humid environments. This means it should do just fine growing inside your home and doesn’t need any special handling in terms of temperature or humidity.
Watering
Catnip prefers average to medium moisture. The plant recovers quickly from wilting, so it’s best to err on the side of dry rather than too wet, which might encourage root rot.
Fertilizer
Feed with a weak liquid fertilizer throughout the growing season; every two weeks is a good rule of thumb. Organic fertilizer is best, as it helps ensure no harmful chemicals that might upset your cat. Check the label of your chosen fertilizer and be sure to use as directed.
Pruning and Maintenance
It’s best to keep your catnip plant from blooming, so be sure to cut off any budding stems before they have a chance to bloom. This will encourage the plant to grow fuller. Regular harvesting of the leaves will keep the plant growing strong—and make for happy kitties, who can eat the leaves fresh or dried. If the plant gets too tall, it is advised that you trim it back to a height of 6 inches to encourage more leaf-rich bushy growth.
Container and Size
Plant your catnip in a pot that is at least 8 inches wide and 8 inches deep. It’s best to avoid breakable materials like clay, just in case your cat gets into the plant and knocks it to the floor.
Potting Soil and Drainage
Any good quality, rich potting soil will be sufficient. Potting soil must drain well and the container must have adequate drainage holes.
Potting and Repotting
Catnip is a perennial plant that generally grows 2 to 3 feet tall when grown outdoors. Indoors, providing you give it enough direct sunlight and the right amount of water, it might grow up to 2 feet tall but not as tall when grown outdoors. In reality, indoor catnip doesn’t have the potency of catnip grown outdoors and it seems more reasonable to grow plants indoors only for a single growing season. If you want to repot a small catnip plant, increase the pot size to one size larger, use fresh potting soil, and be careful not to damage the root system.
Moving Catnip Outdoors for the Summer
Catnip is a very hearty plant, so you can move it outdoors once the threat of frost is over, if you choose.
Considerations
Catnip prefers full sun, but if you experience extremely hot summers, it’s best to give it a shade break in the afternoon.
When to Bring Catnip Back Inside
Catnip can overwinter just fine outdoors, so there’s no need to bring it back in if you don’t want to. Just be sure to cut back any tender new growth to help keep the plant from damage. Of course, if you want to harvest your catnip year-round, bring it indoors before the first frost and care for it as described above.
