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Companion Planting: Good Friends in the Edible Garden
by Ruth McElvain - April 2013

This spring, as you plan your summer vegetable garden, consider companion planting as one of your strategies, especially if you’re interested in organic gardening. For centuries, gardeners around the globe have recognized that companion plantings provide natural insect repellents, collect nutrients for neighbors to share, provide support for flimsy or climbing plants, attract beneficial predators and sometimes provide protection from sun and wind for your more delicate plants.

A classic combination, still used today, originated with the Native Americans. Called the “Three Sisters,” it uses corn as a living trellis for pole beans to climb. The beans fix nitrogen for the hungry corn and the squash enjoys the dappled shade from both while keeping the ground cool for all three.

Harnessing the benefits of companion planting also helps preserve habitats for garden creatures such as toads, snakes, lizards and birds, reducing garden threats and preserving the natural ecosystem. In your planning, remember certain plant combinations need to be avoided so neighbors don’t set up mutually adverse conditions that sabotage each other.    

Companion Plants to Combat Pests
PEST HERB COMBATANTS
Aphid Pennyroyal, spearmint, allium, cilantro, hyssop, nasturtium, sunflowers
Asparagus beetle Parsley, petunia
Bean beetle Summer savory, rosemary, petunia
Carrot fly Rosemary, sage, allium, cilantro
Colorado potato beetle Horseradish, flax, bee balm, marigold.
Cucumber beetle Marigold, nasturtium, oregano, radish
Mosquito Basil, lemon balm, pennyroyal
Nematode French/African marigold, black-eyed Susan, dahlia, pyrethrum daisy (Tanacetum coccineum)
Squash bug Marigold, nasturtium, bee balm, lemon balm, borage, radish
Tomato worm Borage, opal basil, marigold, petunia
Whitefly Nasturtium, marigold, zinnias

Natural Pesticides

Tomatoes are a favorite crop for gardeners, even though growing the coveted red fruit can present many challenges. Nematodes, one major tomato enemy, attack the plant's roots. Reduce the damage of nematodes by planting marigolds at their feet. One Dutch study found that ‘Golden Guardian’ marigold had a 99 percent success rate at killing nematodes, even better than chemical pesticides. Black-eyed Susans, chrysanthemums and dahlias also fight nematodes. These plants will benefit nematode victims including tomatoes, potatoes, okra, peas, beans, sweetpotatoes and peppers.

Marigolds deter many other pests, too, making the flower an organic garden workhorse, so plant it freely throughout your beds. Marigolds target Mexican bean beetles, asparagus beetles, potato bugs, squash bugs, whiteflies and tomato worms. Rabbits and squirrels also don’t like the strong smell, so marigolds are great for a garden border. 

Improving Nutrients     

Neighboring plants can also supply nutrients to your vegetables naturally, which is a plus for organic gardeners seeking to avoid chemical fertilizers. Legumes, for example, fix atmospheric nitrogen at the soil level, and their neighbors get the nitrogen benefits. Heavy nitrogen feeders such as corn, lettuce, spinach, herbs, cabbage and broccoli do well planted near legumes such as beans, peas, peanuts and alfalfa. You can also use the spent legume plants as mulch.

Chamomile and comfrey grown along with members of the onion family, carrots and other root crops such as beets, turnips and radishes feed these potassium lovers and improve their growth. 

Increasing Yield and Flavor

Studies have shown that basil planted within 10 inches of tomatoes increases tomato yield by 20 percent. Borage planted with strawberries not only attracts beneficial predatory insects such as praying mantises that eat strawberry pests, but many believe borage improves the strawberry’s flavor. Taste is subjective, so each gardener must determine individually. But there’s also talk that basil, bee balm and borage improve the flavor of tomatoes. Reports say summer savory improves the growth and flavor of beans and onions, as well.

It bears noting that some combinations are not mutually beneficial. Tomatoes grow better with basil, though basil yield is better on its own. Carrots help tomatoes, but are in turn stunted by them. Individual gardeners should use companion-planting information to decide on a case-by-case basis to decide which results they're looking for. 

Attracting Beneficial Predators

The bee decline over the past few years should make us appreciate the humming industry of all pollinators even more. Many herbs with their simple flowers, nectar and pollen are excellent magnets for bees. It’s good practice to not pinch out tips and buds of every herb – allow a few of each to flower, remembering that bees are drawn to blue, yellow and white blossoms.

Alyssum, marigolds, borage, garlic chives, mustard, parsley, cilantro, morning glory, nasturtium, petunias, yarrow and zinnias put out a siren call to honey, carpenter, bumble and mason bees as well as hoverflies, tachinid flies, yellow jackets and parasitic wasps. These insects are not just pollinators, some also double as predators of harmful insects. The hoverfly in its larval form has an appetite for aphids, and parasitic wasps’ larvae feed on detrimental bug eggs and larvae. It’s just one more reason not to use harsh chemicals, which indiscriminately kill good and bad insects.

Many companion plants attract the bigger predators of bad bugs. For example, sunflowers planted near tomatoes and corn not only attract ants to herd aphids up the stalks, but also provide perches for birds to get to the desirable seeds and then dive into the garden for worms and bugs. Zinnias attract hummingbirds, which also eat whiteflies. Good companions are beneficial in more ways than one. 

Avoiding Bad Combinations

While many plants provide benefits when combined, there are some that don’t. Tomatoes and corn should be separated by at least 20 feet since they attract the same insect pests, while tomatoes and potatoes need the same distance to avoid sharing a blight that is harmful to both. Peas and beans next to onions causes mutual stunting. Nearly all plants dislike fennel near them. Most plants in the mint family, including lemon balm, bee balm and hyssop, are very invasive. Some gardeners just work around their rampancy, while others attempt to contain mint in pots placed near their vegetables. You can also plant them at a distance from your vegetables and sprinkle the leaves around the garden for their benefits. 

Companions for Popular Vegetables

VEGGIE FRIENDS ENEMIES
Asparagus

Asters, cilantro, tomatoes, parsley, basil, comfrey, marigold, strawberries, petunias, carrots

Onions, garlic, potatoes
Beans, pole/bush Carrots, celery, chard, corn, eggplant, peas, cabbage family, radish, strawberries, cucumbers, bush beans only with beets, potatoes Sunflowers, onions; no beets or potatoes with pole beans
Beets Lettuce, onions, cabbage family Pole beans
Carrots Lettuce, onions, tomatoes, flax Dill
Corn Beans, cucumbers, white geraniums, melons, morning glory, peanuts, parsley, potatoes, squash, sunflowers Celery, tomatoes - 20 feet away
Cucumbers Corn, beans, peas, beets, radishes, carrots, nasturtiums Sage, potatoes
Okra Lettuce, peppers, eggplant, peas, basil, cucumbers, melons  
Onions Chamomile, summer savory, carrots, beets, strawberries, cabbage family, lettuce, tomatoes Peas, asparagus
Peas Corn, beans, carrots, celery, cucumber, eggplant, parsley, early potato, radish, spinach, strawberry, sweet pepper, tomatoes, turnips Chives, onions, gladiolas, grapes, late potato
Peppers, hot Tomatoes, bell peppers, okra, cucumbers, eggplant, squash, chard, basil, oregano, peas Beans, cabbage family
Peppers, sweet Tomatoes, parsley, basil, geraniums, petunias, carrots, onions Cabbage family, apricots
Potato Bush beans, cabbage family, carrots, corn, horseradish, marigolds, peas, onion, comfrey, alyssum Asparagus, cucumbers, pole beans, squash, sunflowers, tomatoes
Radish Beets, beans, carrot, cucumber, lettuce, melon, peas, nasturtium, spinach, squash Hyssop, cabbage family
Squash Beans, corn, cucumbers, radishes, melon, onions, borage, marigolds, nasturtium Potatoes
Tomatoes Asparagus, basil, bean, carrots, onion family, cucumbers, marigold, mint, morning glory, nasturtiums, parsley, peas, pepper, bee balm, borage Corn – 20 feet away, cabbage family, potatoes, apricot, dill

Good for the Garden, Good for Us     

The message is clear for organic gardeners and nature lovers. Frogs and harmless snakes eat slugs and other pests when their habitat is safe. Bats consume crazy amounts of mosquitoes. The more the natural system can be in harmony, the better it is for our gardens. Companion planting is a respectable strategy all around and well worth investigating, cultivating and enjoying in the edible garden. Try companion planting yourself – you and your garden will be in good company.

Photos by Ruth McElvain

 


Ruth McElvain moved back home to the South after spending most of her adult life in California. You can follow her experiences in gardening in the South on her blog, The Backyard Dirt

 

       

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