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Healthy Garden Companions

Pairing plants for aesthetic pleasure is the happy occupation of most backyard gardeners. The spear-shaped leaves of daylilies hide the thorny legs of roses with lush splendor. But our ancestors had different reasons to pair plants - to keep them healthy and improve the harvest.

After Kathy Griffin finished her Master Gardener certification in 2001, she became intrigued with the concept of companion plant gardening. Using the book, Great Garden Companions by Sally Cunningham, Griffin worked with these planting principles at the SOU extension on Hanley Road and at her own home. Already an organic gardener, she found herself addicted.

"It's fun," Griffin explains. "It's about synergy."

Success has propelled her investigations. Pairing basil and marigolds with her tomatoes took care of her tomato hornworm problem. "I have very little plant damage," she says. "I haven't seen a hornworm in four years." Another practice that keeps these bugs away is to keep dill in a distant part of the garden, as that plant attracts the hornworm. And by the way, don't put beets near tomatoes, she says. "They attract leaf miners which will skeletonize leaves. Leaf miners are hard to get rid of organically."

Most of the information available is about vegetable gardening, says Griffin. Much of the information is based on observation, rather than scientific findings, so it helps to have an experimental attitude. Some pairings will be successful, while others can turn out to be a bust, she admits.

In her Ashland business Elemental Designs, landscape designer Kathryn Casternovia uses companion plantings in ornamental and vegetable gardens. "I always have it in mind," she says. "There are different reasons to use companion plantings. It's like discovering friends and family."

Some plants are companionable because of what happens under the ground, others because they are deterring bad bugs or attracting good ones. Other reasons include habitat management, like wind abatement and shade screens, she says.

A classic example of companion planting is the American Indian "Three Sisters," corn, beans and squash. Corn (a heavy feeder) provides the trellis for the beans (a light feeder that improves the soil by fixing nitrogen in soil) and squash (a living mulch) keeps the ground cool and its prickly stems help keep animals away from the central stalks, says Casternovia.

Another successful pairing is roses and garlic, an allium, which deters aphids, say our experts. Plus all alliums exude sulfur from their roots and help prevent black spot problems, Griffin explains. So chives, with their exuberant globes of purple flowers are another attractive pairing for roses.

Another way flowering plants are used is to attract good bugs. Small-flowered plants attract lady bugs, an honorable carnivorous insect, so plant alyssum, yarrow, and asters. Flowers can be "trap plants," like nasturtiums which attract aphids away from roses and vegetables.

Encourage beneficial birds, frogs and insects. "Don't kill anything," exclaims Griffin. Those nasty-looking black ground beetles are among your best friends when it comes to getting rid of slugs and snails.

It can be overwhelming, so start small, advises Griffin. Remember, you want to let these plants do the work for you. Begin with a specific problem, such as aphids on roses, and let your knowledge grow with your needs.

Some pairings may be unfounded, but are fun anyway, says Griffin. Folklore declares that vegetables grown with tarragon and marjoram have improved flavor. It's up to you to decide about the truth of this folk story.

Healthy Garden Companions