Put companions to work in the gardens

Chattanooga Times Free Press, Jul 24, 2010

Companion gardening refers to ways plants interact with each other in the garden. One plant may attract beneficial insects for other plants. Other plants may provide shade, fertilizer or weed control that enable nearby plants to thrive. Some plants grown together may help one or both. For example, growing basil and tomatoes together may improve the health, flavor or yield of tomatoes.
Some vegetables just don’t get along. They can’t stand being planted near one another. Garlic and onion can stunt the growth of beans and peas. Kohlrabi can stunt the growth of tomatoes. Beets and pole beans stunt each other’s growth. Most of these relationships were discovered by observant gardeners. More research is needed to fully explain what is going on.
GOOD COMPANIONS
Growing multiple species in the garden enhances biodiversity and encourages beneficial insect populations. Flowers and perennial plants may provide habitat and food sources for predatory beetles. Other plants attract bees and butterflies which help manage pests.
Researchers found that mixing broccoli varieties reduces aphid infestation. The theory is that beneficial connections between plants confuse pest insects. Some plants repel pests. For example, onions and leeks grown alongside carrots can act as a repellant to the carrot fly.
Legumes, such as peas, beans, and clover, have the ability to pull nitrogen out of the air and helps these plants grow without added fertilizer. Neighboring plants reap benefits as well. Beans are sometimes inter-planted with corn to take advantage of this wonder of nature.
Some plants release chemicals from their roots or aerial parts that repel pests and protect neighboring plants. For example, a crop of rye can be planted then rolled flat just before tomatoes are planted. The rye mulch prevents weed germination by shading the ground. Rye roots release a chemical that inhibits weed growth.
Trap crops lure pests away from the main crop. They are more attractive to pests than the main crop. The trap crop is often planted around the perimeter of the garden. I have used eggplants to trap flea beetles away from tomatoes and cucumbers. Nasturtiums are planted around lettuce and cabbage. Some egg-laying insects tend to prefer the nasturtium.
THREE SISTERS GARDEN
Companion planting is not a new idea. There is evidence of farmers using these methods dating back to ancient Roman times. A great example of a companion garden comes from Indian lore. According to Iroquois legend, corn, beans, and squash are three inseparable sisters. They only grow and thrive when planted together. Corn, beans and squash were among the first crops grown by early societies. Celebrations took place around planting and harvest seasons. By retelling stories and performing annual rituals, Native Americans passed down the knowledge of growing, using and preserving the Three Sisters through generations.
Corn, beans and squash complement each other in many ways. Corn grows tall providing a pole for bean plants. Beans have special roots that capture nitrogen. Bean vines help stabilize corn plants, keeping them from blowing over in the wind. Squash vines grow between corn and bean plants. They become living mulch, shading emerging weeds and preventing soil moisture from evaporating. This type of garden provides long-term soil fertility.
It also is a healthy diet. Corn is a good form of carbohydrates. Beans provide fiber and protein. Squash adds nutrients not found in the other two plants. All three crops can be stored for relatively long periods to provide food throughout the winter.
See UT Publication W235-F for more information on companion planting and organic gardening ideas go to www.utextension.utk.edu/publications.
Contact Tom Stebbinis at 855-6113 or e-mail tstebbins@utk.edu.
Copyright Chattanooga Times Free Press Jul 24, 2010
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