How to Grow Catnip Indoors and Outside, According to Horticulturists

Growing vegetables and herbs for your own kitchen can be gratifying, but don't forget about your feline companions. Catnip (Nepeta cataria) is a perennial herb that's part of the mint family; while it can be ornamental, it's primarily grown for cats to enjoy. Fortunately, you can grow this plant indoors and outside—just follow these steps, and you (and your cat) will be ready for harvest in no time.

Starting From Seed

If you live in zones 3 to 9, then you can sow catnip seeds outdoors between spring and late summer. Otherwise, starting them indoors is the better option. 

“Catnip seeds have a low germination rate, unless they undergo stratification,” says Angelika Zaber, a lawn care specialist for Online Turf. “To improve their chances, freeze the seeds overnight, then soak them in water for 24 hours before planting. Once prepared, sow them in a sunny spot with well-draining soil.”

Catnip seeds can also be germinated in a moist—but not dripping—paper towel, says Ward Dilmore, founder and head landscape designer at Petrus Landscaping. First, spread the seeds on one side of the paper towel, and then fold it closed.

“You can then put it into a plastic bag, which will mimic the humidity of a greenhouse,” Dilmore says. “After a few days they should germinate. Plant them about 1/8- to 1/4-inch deep in potting mix, and placed them a sunny spot. Make sure the soil is kept moist as the seedlings grow.”

Growing Catnip in Containers

Catnip can be invasive and its growth can be controlled and better managed when planted in a container; good drainage is the most important consideration.

“You want to pick a pot that's large enough to accommodate the growth of its roots, but not too large that waterlogging can happen,” says Tammy Sons, founder and CEO of TN Nursery. “Always repot when the plant becomes root-bound.”

Planting Outdoors

Catnip needs space to grow, and can vigorously spread if it's not properly maintained—again, it's best grown in containers. “It can sometimes become overgrown and invade other plants in your garden, but it can easily be cut back,” says Dilmore. “Plus, cutting catnip back in the fall can help keep it controlled, and can encourage new growth in the spring.” 

Care Guidelines

Your approach to catnip care will be mostly the same regardless of whether you're growing it indoors or outside, says Zaber. However, there are a few key differences to know before you start.

Sunlight

“Catnip needs six hours of sunlight, and should be placed next to a sunny window when grown indoors,” says Zaber. “If grown outside, it’s important to choose a sunny spot. However, if you live in one of the warmer zones, the plant may benefit from some afternoon shade.”

Watering

When it comes to watering, containers tend to dry out faster than soil in the ground. Check the soil regularly and water the plant as needed, ensuring it stays moist, but not waterlogged. “Catnip is somewhat drought tolerant once it’s established,” Dilmore says. “This would be after a year or two of planting.”

Soil

Catnip prefers soil with a neutral pH, says Sons, but warns against excessive fertilizer. “It needs to be fed very lightly if fertilizer is being used, because fertilizers can reduce the oil content that cats love."

Precautions

Finally, since catnip is known for its effects on cats, Zaber suggests protecting the plant when growing it outside.

“It's best to surround it with wire fencing with small holes, or place some bamboo sticks in the area,” she says. “This will help prevent neighboring cats from lying on top of it. However, the wire method may be more effective, as cats may still attempt to eat the plant.”

Pests and Diseases

Catnip rarely has problems with pests or diseases, says Zaber, but you’ll want to avoid overwatering, as this can cause root rot. “In dry summers, the plant may also develop powdery mildew,” says Zaber. “If this happens, remove any affected leaves and apply a suitable fungicide.”

Whiteflies and spider mites can occasionally attack catnip. “If the air circulation around your catnip is poor, some select pruning can help,” says Dilmore. “Neem oil is a great natural option for dealing with whitefly if the infestation isn’t too severe.”

Common Mistakes

The most common catnip care mistake is overwatering, says Zaber, which can cause the plant's leaves to curl, or to turn brown and spotty. To fix this, simply reduce how much you water the plant.

“Another common mistake is giving the plant too much or too little sunlight,” she says. “Too much sun can scorch the leaves and burn the plant, while too little will stop the plant from thriving and producing as much foliage.”

Dilmore warns against planting catnip too close to other plants. “If they grow too well, they can outgrow other plants,” he says. “Catnip is best planted on the edges of gardens.”

How to Propagate

Catnip can be propagated either from seed or stem cuttings. Seeds can be purchased in stores, says Zaber. If you already have an existing plant, look for dried flower stalks and crush them to release the seeds. For best results, ensure your seeds undergo stratification before planting.

In the case of stem cuttings, choose young, vibrant stems. “Using sharp scissors or a knife, snip just below a node,” says Zaber. “The cuttings should be around 4 to 6 inches in length. Remove the lower leaves to allow the plant to focus on root development. You can then place the cuttings in either water or soil.”

If propagating in water, simply place the cutting in a glass of water and change it every few days to keep it fresh. “If you're using soil, dip the cut end in rooting hormone before planting it in a pot with well-draining soil mix," says Zaber. "Make sure it stays moist, but not waterlogged."