Marigolds’ fragrance deters scent-averse pests from feasting on tomatoes, while cockscomb acts as a barrier to slow the spread of disease or pests to neighboring peppers.
We call it “chemistry.” That special combination of quirks and qualities that makes a couple good together. “She thinks I’m funny.” “He makes me laugh.” They’re made for each other. It happens in the plant world, too.
When Cherokee Indians combined a trio of vegetables in their early American gardens, all three plants thrived. The beans, corn and squash plants each brought something to their shared space that helped the others flourish. Squash leaves protected sister plants from pests and crowded out invading weeds. Beans “fixed” essential nitrogen in the soil to promote siblings’ leaf and root growth. And corn served as a natural beanstalk for the beans that grew at its feet. Because the plants were relational, the Cherokee named them the Three Sisters. Our gardening ancestors had discovered what science now understands to be some very real and valuable reciprocity in the relationships that grow in a garden. They may not have known why, but they knew it worked.
Today, gardeners who grow complementary plant species side by side to take advantage of their natural symbiosis are practicing “companion planting.” It’s a conscious coupling that can help increase yield, manage disease, control pests, conserve water and improve soil fertility. And it works for a variety of reasons, all related to the richness of nature’s diversity.
In the northwest corner of Lewis Ginter Botanical Garden, adjacent to the glass conservatory, an army of volunteers grows thousands of pounds of fresh vegetables every year. The garden donates the produce to FeedMore, where it supplements healthy meals in the food bank’s Meals on Wheels and Kids Cafe programs. Chelsea Mahaffey is the horticulturist responsible for the Community Kitchen Garden, and she’s something of a plant matchmaker.
Mahaffey practices companion planting because it is both efficient and effective. “I fill the beds with companion plants, which smother the weeds (less work), attract beneficial insects (less spraying) and attract more pollinators (more fruit).”
Weeds hungry for cabbage and onion are no match for a carpet of English thyme, which also attracts beneficial insects.
When she grows a traditional combination of marigolds and tomatoes in the Community Kitchen Garden, the fragrance of the ruffled orange blossoms protects their companion tomatoes. “Bugs that like tomatoes don’t like the scent of marigolds,” Mahaffey explains. Nasturtiums deter a host of pests the same way. Basil repels mosquitoes. Marigolds and potatoes both discourage Mexican bean beetles, and radishes fend off cucumber beetles. It’s an important part of organic gardening.
The checkerboard of peppers and cockscomb (Celosia cristata) growing in the Community Kitchen Garden serves as another form of pest control: Plant diversity interrupts the progress of pests that might prey on partner plants. “Cockscomb acts like a barrier to slow the spread of disease or alleviate pest pressure,” Mahaffey says. “I can monitor the health of the pepper plants and catch a problem early — maybe prevent a total loss if we have trouble.”
Nor could the weeds compete with the carpet of English thyme she planted under the cauliflower crowns last year. “It was beautiful,” Mahaffey says, “and we only had to weed the bed four times the whole season. Next spring, the thyme will help with early season pest control because beneficial insects love herb flowers.”
In the same bed, companion planting increased yield by making better use of space. “I added thyme and onions to the cabbage bed (that holds 24 heads of cabbage) ... Now my bed has 24 cabbages, 24 groupings of thyme and 50 onions.” Surprisingly, she also found that she was watering the same amount with the companion plants or without.
It turns out companion plants can be a gardener’s best friends, too.
