Catnip, or cat mint, is known to botanists as Nepeta cataria. The herb is known to most felines as spellbinding, to which any catnip growing enthusiast will quickly attest. This Eurasian native has become naturalized throughout most of the world, and is a hardy perennial in USDA Planting Zones 6 through 10. In cooler regions, Nepeta can be brought indoors to over-winter.
Use clean, sharp scissors to cut your catnip plant back as soon as it's through flowering for the year. If you're located in a temperate region, there's nothing further you need to do to winterize this plant.
Dig garden catnip up in the fall before the first predicted hard frost. Pot it in a mixture of equal parts peat moss, loam and sand or perlite. Water it enough to evenly moisten the soil surface.
Move the catnip to a cool, well-lit room for the winter. A constant temperature of around 48 degrees F is perfect. Hang the plant well out of reach if you have an indoor cat. Kitty will literally love this plant to death if she gets her paws on it.
Shear the cat mint back to about ½ to 1 inch tall when the foliage dies back completely.
Water catnip sparingly throughout the winter. Barely moisten the surface of the soil about once monthly. No fertilizer is needed.
Move the plant back outside in the spring after all danger of frost has passed for your area. Plant it back in its garden spot, pot and all. This will contain the mint family member and prevent it from rapidly raging out of control. Resume your normal growing season maintenance program for this plant.
Divide your catnip as soon as new spring growth emerges, if you wish.