Control Invasive Spread

Catnip, like its close cousin mint (Mentha spp.), hardy in USDA zones 4 through 9, grows invasively. To keep it from choking out the rest of the garden, grow catnip in containers sunk in the ground. Leave 1 inch or more between the top of the pot and the soil line; if you see stems leaning over the side trying to touch the soil, cut them back. Each place a catnip stem touches the ground, it has the potential to put down roots. Keep the flowers picked before they go to seed; otherwise, you'll have catnip popping up all over the place.

Sun, Space and Water

Space catnip plants 18 to 24 inches apart in a sunny to partly shaded garden bed. If you're not planting a large number of plants, consider planting in informal clumps rather than formal rows for a natural look. This self-sustaining plant tolerates dry, rocky soil and periods of drought. For lush, abundant growth, however, water catnip when the soil starts to dry out on top through the dry season.

Fertilize Sparingly

Catnip needs very little fertilizer to grow well, especially in already fertile garden beds. Fertilize using an organic, balanced 6-6-6 fertilizer and apply only 1 teaspoon to each plant. Apply the fertilizer once in the spring at the beginning of the growing season and again in midsummer.

Problem Free -- Mostly

The strong scent of catnip leaves that drives cats crazy also drives away pests. Even disease problems are rare for this herb. In areas where deer browse, catnip is usually safe. Cats, however, can decimate a clump of vigorous catnip by rolling in it and nibbling the stems until it's flattened. If your own or a neighbor's cat is particularly enamored with this herb -- and that's not why you're growing it -- put a wire cage over the top to protect it.

Trimming Catnip

From spring through fall, pinch back new stems to keep the overall shape compact and bushy. Take one to two leaf sets off for a minimal reduction in size. For a more drastic reduction, you can pinch back the stalks until it is the size and shape you want. In the summer, when catnip starts blooming, pinch off the flowers to encourage more leaf production. You can harvest catnip stalks as you need them by cutting each branch near the soil line.