Organic gardeners know that a diverse mix of plants makes for a healthy and beautiful garden. Many also believe that certain plant combinations have extraordinary (some even believe mysterious) powers for helping each other grow. Scientific study of companion planting has confirmed that some combinations have real benefits unique to those combinations. And practical experience has demonstrated to many gardeners how to mate certain plants for their mutual benefit.
How does companion planting work?
Roses and chives: Gardeners have been planting garlic with roses for eons, because garlic is said to repel rose pests. Garlic chives probably are just as repellent, and their small purple or white flowers in late spring looks great with rose flowers and foliage.
Tomatoes and cabbage: Tomatoes are repellent to diamondback moth larvae, which are caterpillars that chew large holes in cabbage leaves.
Cucumbers and nasturtiums: The nasturtium's vining stems make them a great companion rambling among your growing cucumbers and squash plants, suggests Sally Jean Cunningham, master gardener and author of Great Garden Companions. Nasturtiums "are reputed to repel cucumber beetles, but I depend on them more as habitat for predatory insects," such as spiders and ground beetles.
Peppers and pigweed or ragweed: Leafminers preferred the weeds to pepper plants in a study at the Coastal Plains Experiment Station in Tifton, Georgia. Just be careful to remove the weeds' flowers before they set seed or you'll have trouble controlling the weeds.
Cabbage and dill: "Dill is a great companion for cabbage family plants, such as broccoli and brussels sprouts," Cunningham says. "The cabbages support the floppy dill," while the dill attracts the tiny beneficial wasps that control imported cabbageworms and other cabbage pests.
Corn and beans: The beans attract beneficial insects that prey on corn pests such as leafhoppers, fall armyworms and leaf beetles. And bean vines climb up the corn stalks.
Lettuce and tall flowers: Nicotiana (flowering tobacco) and cleome (spider flower) give lettuce the light shade it grows best in.
Radishes and spinach: Planting radishes among yor spinach will draw leafminers away from the spinach. The damage the leafminers do to radish leaves doesn't prevent the radishes from growing nicely underground.
Potatoes and sweet alyssum: The sweet alyssum has tiny flowers that attract delicate beneficial insects, such as predatory wasps. Plant sweet alyssum alongside bushy crops like potatoes, or let it spread to form a living ground cover under arching plants like broccoli. Bonus: The alyssum's sweet fragrance will scent your garden all summer.
Cauliflower and dwarf zinnias: The nectar from the dwarf zinnias lures ladybugs and otherpredators that help protect cauliflower.
Collards and catnip: Studies have found that planting catnip alongside collards reduces flea-beetle damage on the collards.
Strawberries and love-in-a-mist: Tall, blue-flowered "love-in-a-mist (Nigella damascena) looks wonderful planted in the center of a wide row of strawberries," Cunningham says.
Marigolds and Melons. Certain marigold varieties control nematodes in the roots of melon as effectively as chemical treatments.