Catnip is a common herb that thrives in much of North America and is very easy to grow. While you've probably heard that catnip makes cats something like tipsy, you might not know that this effect is an inherited trait and does not affect all cats. And if you're planning to plant catnip—for your cat or yourself—you should realize that there are different types of catnip and that all common types are invasive. This means they can take over your garden even if they don't take over your cat's mind.
Taxonomy and Botany of Catnip Plants
Plant taxonomy classifies catnip plants as Nepeta cataria. Note that the common name, "catmint" is preferred in the U.K. It may be tempting to use the two names interchangeably, but in the U.S. we tend to reserve "catmint" for the ornamental relatives of N. cataria, such as Nepeta x faassenii and Nepeta mussinii. In any case, look for the scientific, or botanical, name when shopping for plants to be sure you get the right type of catnip.
Nepeta cataria plants are classified as herbaceous perennial herbs. Catnip plants have naturalized in various parts of North America, and even where they are not perennial, they will likely reseed. In fact, many gardeners find catnip to be too weedy and too aggressive of a spreader to grow it in their landscapes.
Features of Catnip Plants
Catnip plants can grow up to 3 feet tall and wide. Their small white or lilac-colored flowers grow in clusters. The stems of these fragrant plants have the squarish shape typical of the mint family to which they belong. Catnip plants enjoy sun and are drought-tolerant ground covers, making them a good choice for sunny, dry areas where many other plants would struggle. But they offer little ornamental value. Nepeta cataria is the preferred herb to grow for cat-lovers; fewer cats are attracted to the ornamental types, such as Nepeta mussinii.
Where to Plant Catnip
Native to Eurasia, catnip plants can be grown in USDA plant hardiness zones 3 through 9. They do best in full sun to partial shade. Like so many herbs, this perennial thrives in poor soil that is well-drained. Catnip plants prefer a slightly alkaline soil but are not very fussy about the ground in which they grow, as long as their roots are not constantly sitting in water.
Caring for Catnip
To prevent damage from unwelcome neighborhood cats, consider protecting your catnip with some type of enclosure. You should not have to protect them from insects and rodents, as few of these pests are drawn to catnip. That is a good thing because you want to give your pets a safe, healthy harvest to enjoy and not expose them to toxic treatments.
To contain and shape catnip plants, pinch them often while they are growing, to obtain dense, well-shaped plants. You can do the same with the related ornamental plants in the genus, such as 6 Hills Giant catmint (Nepeta x faassenii '6 Hills Giant'). This practice will prevent them from getting too big and will give you nice, bushy herbs.
Harvest catnip upon flowering, on a dry, sunny day. Late morning is a good time to harvest after the dew has dried but before the day heats up. Cut off the whole plant at the base, and hang it upside down, as soon as possible, in a dark, dry, well-ventilated place (for example, an attic). Store dried leaves, stems, and flowers in freezer bags to preserve the potency of the oil inside them. These steps help minimize the loss of the oil, which is the stuff that makes your cat go wild.
Uses in Landscaping
Nepeta cataria catnip is usually grown mainly with cats in mind. As part of a "cat-friendly yard," you can grow Nepeta cataria for your cats to enjoy outdoors, cut fresh stems to bring to your pets indoors, or harvest and dry the plants for future use.
If you'd like to grow catnip for landscape design, choose an ornamental variety, such as Nepeta mussinii. This is an attractive plant that stays about 1 foot tall. Nepeta mussinii has a spreading habit and is often used as a ground cover. Both Nepeta mussinii and Nepeta cataria are deer-resistant but do attract butterflies.
Uses in Food and Medicine
Catnip isn't just for cats. Like so many herbs, it also has uses in food and medicine, whether used fresh or dried. For example, tea made from the leaves and flowers of Nepeta cataria are drunk to relieve coughs. Catnip leaves and shoots can be used as ingredients in sauces and soups. The oil extracted from catnip plants is even used in natural mosquito repellents.
What Catnip Does to Cats
Most people associate catnip with the psychoactive properties that it has on cats. The effect occurs when the leaves are eaten or when the plant's fragrance is inhaled by cats. In fact, simply smelling catnip is often enough to cause cats to react to it, which is why you sometimes see them rolling in it. The resulting drug "trip" comes courtesy of a chemical called nepetalactone.
The effect of catnip is not the same for all cats. The reaction is due to an inherited trait, and only some cats are sensitive to nepetalactone. Other cats will turn up their noses when presented with the plant (whether fresh or dried). Cats that react to catnip generally respond not only to the leaves but also to the flowers and stems. And do not worry: Nepetalactone is not addictive or harmful to cats, according to many veterinary sources.
How to Contain Catnip
While you can give your cats the green light to eat catnip, it's not wise to issue an "all clear" signal when it comes to using it in your landscaping. Catnip plants may be considered invasive plants. They will spread out of control unless you take measures to keep them from doing so (which means extra work for you). Only you can decide whether or not the benefits of the herb outweigh this drawback.
The plants will reseed all over your property if you let them. This means you will have new plants springing up in unexpected places for years to come. If you like a tidy landscape, you may come to regard catnip as more of a weed than an herb. But you can strike a compromise and have the best of both worlds by preventing the plant from blooming (no flower means no seed): Simply pinch off the top of the plant when flowers start to form.