A companion plant supplies help for neighboring plants in the form of shade, insect control or other support. Catnip on its own has many uses--it's beloved by cats, and can be added to salads or used for soothing teas by humans--but it also helps deter garden pests that may otherwise inhabit (and destroy) other garden plants. That makes it a good companion plant for any garden.
Catnip is a leafy perennial plant that resembles mint and in fact is part of the mint family. It's edible for both cats and humans. The scent of catnip is mild but grows stronger if you break or rub the leaves. Catnip will bloom, developing small clusters of blue or purple flowers.
Plant catnip via seed or seedling. You can start seeds indoors or sow them directly in your garden near plants you wish to help. Herb Gardening advises spacing catnip about 15 to 18 inches apart. When choosing where to plant, keep in mind the plants may grow up to 4 feet tall. Catnip prefers sunny areas with well-draining soil. Soil temperature should be 65 degrees F or warmer when you plant, according to Simple Gifts Farm.
Water new catnip enough to keep soil moist until the plants become established. After that, you can taper watering down to once weekly, according to Simple Gifts Farm, but if plants show signs of drooping or wilting before a week has passed, water again. Hot weather may naturally increase catnip's water needs.
According to GH Organics, catnip deters garden pests such as flea beetles, Japanese beetles, aphids, weevils, ants, squash bugs and mice. You should plant catnip around plants that are prone to these pests.
As catnip is very attractive to most cats, you may attract more of them to your garden. Cats may consume your catnip and deposit feces and urine on your plants while there. Be aware of this if you live in an area frequented by stray cats or the neighbors'.
Catnip is a good companion plant to collards, according to Organic Gardening, because it deters flea beetles, which damage collards. Catnip also benefits tomatoes, squash and any other vegetable plants affected by aphids or squash bugs. According to Our Herb Garden, catnip also helps beets, pumpkin and hyssop, and Hobby Farms says catnip benefits potatoes by repelling the Colorado potato beetle.