Many North American Indian tribes have variations on the legend of the "three sisters" — corn, beans and squash — which explains the necessity of planting these three vegetables together. Where the legend originated is unknown, but the Wampanoag tribe related it to the early European settlers when explaining what and how to plant to get them through their first winter.
Greg Williams, retail manager of Ashland Greenhouses, uses this system himself. "You interplant corn and beans, so you don't have to trellis your beans," he says. "Corn uses so much nitrogen, and beans fix nitrogen. It's very effective, in my experience."
The advantages of planting corn, beans and squash together seem obvious now. Corn provides support for the beans. Beans stabilize the corn plants in the wind and fix nitrogen in the soil. And the squash leaves shade the soil, keeping it moist and discouraging weeds.
Using heirloom corn varieties that grow tall helps this system work. Preferred varieties include Indian Corn, Anasazi, Iroquois, Black Aztec, Black Mexican, Bloody Butcher, Blue Clarage, Cherokee Blue & White, Mandan Red, Rainbow Inca and Texas Honey June.
Recommended bean varieties that work well as companions are Scarlet Runner, Genuine Cornfield, True Cranberry, Cornfield and Hopi Purple.
Almost any variety of squash or pumpkin will work in this system.
Three, basic planting styles are used in most "three-sisters" gardens. East of the Mississippi, tribes used the Wampanoag style; in the Plains, they developed Hidatsa style; and the Zuni developed the Zuni "waffle garden" to conserve water.
In the Wampanoag garden, raised mounds about 4 to 6 inches high and about 18 inches in diameter are used for planting. The top is flattened with a lip to conserve water, and four corn kernels are planted on top. Four bean plants are planted farther down the mounds, one on each side. Squash is planted between the mounds. There should be 4 feet between the centers of the mounds. Corn is planted first, and once it is 4 inches high, the other two crops are planted.
Hidatsa-style gardens are planted in staggered, alternating rows. Corn and bean plants are in alternate rows, but every fourth row is squash. Squash also is planted on three sides of the garden — east, south and west. Either of these systems should work in our climate.
The Zuni style is for desert agriculture.
"Companion planting creates beneficial plant relationships by taking advantage of certain biological mechanisms within different plants. Some of the most common mechanisms we see in companion planting include symbiotic nitrogen fixation, biochemical pest suppression, nurse cropping and the creation of beneficial habitats," says Maud Powell, Oregon State University Extension Small Farms instructor in Central Point.
Knowing which plants like to be together — and which don't — can greatly enhance success in your garden. Beans and peas do not like onions, so do not grow them near each other. You can grow beans and peas with most other vegetables, including potatoes, herbs and also strawberries.
Beets and beans don't do well together. Neither do corn or cucumbers and tomatoes. Members of the cabbage family should be kept away from strawberries, tomatoes and pole beans. Potatoes need to be separated from pumpkins, squash, cucumbers, sunflowers and tomatoes.
You may plant asparagus near tomatoes and basil. Beets like cabbage, onion families and lettuces. Carrots do well paired with radishes, peas, lettuce, rosemary, sage, onions or tomatoes.
Cabbages enjoy the company of herbs, celery, beets, onions, spinach and chard.
Cukes can be paired with beans, corn, peas, sunflower and radishes. Pepper plants and tomatoes do well together.
Eggplants seem to like only beans and marigolds. Spinach prefers strawberries and fava beans. Radishes will pair with peas, nasturtium, lettuce and cucumbers. Peas also do well with turnips, carrots, radishes, cucumber, corn and beans.
If you take these relationships into consideration when planning your garden, your plants will appreciate it, and your yield should improve.