In the rows where your vegetables grow, good neighbors can make all the difference by helping with everything from pest control to providing windbreaks and shade.
Pam Zaklan, who has been an Oregon State University Extension Service Master Gardener program since 2011, has long known the affinity of plants for each other. She came about her knowledge of companion planting through the lessons she has learned from vegetable gardening for 50 years. The more she researched, the more she understood the synergistic effect certain plants have for each other.
“There are different interactions from planting certain vegetables, herbs and flowers together,” said Zaklan, president of the Josephine County Master Gardener Association chapter. “It’s not just about attracting beneficial insects; you have to know what the plant’s needs are and plant something that will complement that.”
For instance, in her garden, Zaklan struggles with difficult-to-control squash bugs. She discovered there are a range of plants to intermingle with squash to fend off the pests, including chives, mint, oregano, marjoram, calendula and dill. Apparently, squash bugs are deterred by the odor of these plants. She also puts vine-like nasturtium among the vines to confuse the bugs, which will go for the nasturtiums thinking they are squash.
The best-known example of companion planting is the “Three Sisters” of corn, pole beans and squash or pumpkins. The trio was first planted by Native Americans and adopted by European settlers in the 1600s. The corn provides support for the climbing beans, which pull nitrogen from the air and share some of it with the corn’s roots. The squash or pumpkins enjoy the dappled sun from the corn and shade the ground, acting as a living mulch to keep weeds down and conserve water for the three crops.
Zaklan adds sunflowers as a fourth sister to bring in pollinators and give the vines another structure to grow on. And as the sunflowers take nitrogen from the soil, the beans put it back in.
“I grow tall, medium and low sunflowers,” she said. “Oh gosh, it’s beautiful.”
There is a riot of reasons to use companion planting. It helps with pest control by repelling “bad” insects and by drawing in “good” predator insects to feed on them. It fixes nitrogen, which benefits any plants growing nearby. Tall plants provide shelter or shade and act as trellises as in the Three Sisters tradition. Zaklan said there’s also research to show planting certain plants next to each other can enhance flavor, though that benefit is more nebulous.
“Some plants can be used as sacrifices,” she said. “I plant calendulas alongside beds of roses or whatever plants aphids like to glob onto. They’ll attract the aphids and keep them from bothering the roses. They also attract bees and reseed themselves and come up with beautiful little orange flowers that bloom and bloom. I had them in among my butter lettuce and had no aphids.”
It takes time to learn the whole range of plants that benefit each other, but Zaklan, who owns a small farm with her husband, helps out by sharing what she’s learned from research and hands-on experience.
- Use four o’clocks to deter Japanese beetles from roses.
- Plant mustard to deter cabbage worms and harlequin bugs from cabbages, broccoli, cauliflower and Brussels sprouts.
- Garlic deters rabbits as well as tree borers, aphids, cabbage looper, codling moths, Japanese beetles, snails, carrot root flies, ants and cabbage maggots. It is especially beneficial when planted near, roses, cucumbers, peas, lettuce or celery.
- Spearmint and peppermint are useful in attracting bees and repelling black flea beetles, ants, mosquitoes, white cabbage butterflies, aphids, and cabbage maggots. Do not plant mint near parsley. Plant mints in containers as they can easily get out of control.
- While horseradish is the most commonly recommended companion plant for potatoes, other plants that are said to benefit the potato plant include green beans and peas, the brassicas (broccoli, Brussels sprouts, cabbage, cauliflower), corn, lovage, marjoram, marigolds, nasturtiums, parsnips, watermelon and sweet alyssum.
- For squash bugs, plant mint, chives, garlic, onion, tansy, radishes, nasturtiums, marigolds and bee balm near and among vines of winter and summer squash.
Some books Zaklan recommends are “Great Garden Companions” by Sally Jean Cunningham; “Carrots Love Tomatoes: Secrets of Companion Planting” by Louise Riotte; and “The Complete Guide to Companion Planting” by Dale Mayer.
