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. As a result, it may be tempting to use the two names interchangeably. However, I prefer a more restrictive usage, whereby "catmint" is reserved for a different member of the same family, namely, Nepeta mussinii. Where I refer to the latter, I employ the scientific name, in order to avoid confusion with the subject of this page, which is Nepeta cataria.
Nepeta cataria plants are classified as herbaceous perennial herbs. Catnip plants have naturalized in parts of North America. Even where they are not perennial, they may reseed. In fact, some of you may find catnip too weedy and too aggressive a spreader to grow it in your landscape.
Characteristics of Catnip Plants
Catnip plants can attain a size of 3 feet tall and 3 feet 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, whether herb or weed (creeping charlie, for instance). Catnip plants enjoy sun and are drought-tolerant ground covers, making them good candidates 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 Nepeta mussinii.
Planting Zones, Sun and Soil Requirements
Native to Eurasia, catnip plants can be grown in North America in planting zones 3-9.
Grow them in full sun to partial shade. Like so many herbs, this perennial thrives in poor soil that is well-drained. Catnip plants like a slightly alkaline soil.
Care Tips: Pinching and Drying
Unless you can tolerate damage, protect these herbs from cats by, for example, fencing them off. Pinch them often while they are growing, to obtain dense, well-shaped plants.
I do the same with my 6 Hills Giant catmint, to keep it from getting too big.
Harvest them 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). Following this regimen will allow you to minimize loss of volatile oil (which is the stuff responsible for driving your cat wild).
Uses in Landscaping
The catnip plants that I discuss here (Nepeta cataria) are used primarily in landscaping for cats. As part of the "cat-friendly yard," grow them for your cats to enjoy outdoors or harvest them for drying. But if you are more concerned with your landscape design than with your cats, grow Nepeta mussinii, instead. The latter is a more attractive herb, as it stays shorter (1 foot tall). Nepeta mussinii has a spreading habit and is used as a groundcover. Both Nepeta mussinii and Nepeta cataria are deer-resistant but do attract butterflies.
Medicinal and Culinary Uses, Psychoactive Properties -- and a Warning
These perennials are not just for cats: like so many herbs, they also have culinary and medicinal uses, whether used fresh or dried.
People have traditionally drunk a tea made from the leaves and flowers to relieve coughs, for instance. The 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. Store dried leaves and flowers in freezer bags to preserve the potency of the oil.
These uses notwithstanding, what most people are interested in are the psychoactive properties demonstrated by catnip plants when their fragrance is inhaled by cats (and inhaling it is, in fact, enough, which is why cats can "flip out" just by rolling in it). The resulting "trip" comes courtesy of a chemical named "nepetalactone." The impact is not the same on all cats; only some are sensitive to nepetalactone. According to How Stuff Works, "The catnip reaction is inherited, and some cats are totally unaffected by it.
Large cats like tigers can be sensitive to it as well."
While you can give your cats the green light to eat catnip, I can't issue an "all clear" signal when it comes to using it in your landscaping. Catnip plants may be considered invasive plants. Only you can decide whether or not the benefits of the herb outweigh this drawback.