Creating a mutually beneficial garden

Whether looking to repel pests, attract beneficial insects or improve soil health, companion planting — or planting mutually beneficial plants together — is a helpful tool to level up any size garden.

“It (companion planting) can be interpreted many different ways,” said Joe Storlien, a Stearns County master gardener through the University of Minnesota Extension. “To me, it is just kind of a gardening strategy involving growing multiple types of plants — could be fruits, flowers, vegetables, herbs — together in a similar space. Generally, that style of planting is considered more resilient and certainly more biologically balanced than a single crop or monoculture system.”

According to the UMN Extension website, many companion planting practices have been passed down through generations, with some common pairings being difficult to find research to support. The UMN Extension focuses on providing research-based information, which master gardeners help distribute. As a master gardener and an environmental studies professor at the College of St. Benedict and St. John’s University, Storlien enjoys gardening as a way to combine different aspects of his life.

“It (gardening) has become a great outlet for me between both my professional life and just hobbies and passions,” he said.

Having grown up in southwest Minnesota and studied at St. Cloud State University and Texas A&M University, Storlien settled back in Stearns County in 2014 and now has plenty of experience with companion planting in his own garden at his home near Avon. Storlien said he tends to categorize the benefits of companion planting into three main categories: improving plant health through reducing susceptibility to certain pests or diseases, enhancing ecological function by having certain plants in the same area, and maximizing yield in limited spaces.

In his garden, Storlien said he has experienced damage to brassicas like broccoli, cabbage and kale by flea beetles.

“And one trick backed by some research is that you can companion plant in some spicy brassicas, so other plants in that family like arugula, nearby,” he said. “This serves as a trap crop for the flea beetle; they’re very strongly attracted to the spicier brassica species. And I much prefer sacrificing some little quick-growing arugula greens to help keep those beetles off my larger brassica crops, which are kind of the main crops I like them to stay away from.”

According to the UMN Extension, the scent of certain plants can repel insects, attract insects or mask the scent of desirable plants. Like with basil and tomatoes, the smell of the basil has been shown to help repel thrips.

“Basil and tomatoes go hand in hand not only for culinary purposes, but actually, there are quite a few benefits of reducing some pests there,” Storlien said. “And then, there are some studies that have also found that basil will actually help promote tomato growth and possibly even enhance some of the flavor profile in the chemistry of tomatoes, which is really fascinating.”

Attracting pollinators and beneficial insects through companion planting can also have a positive effect on backyard gardens.

“Around a couple of the borders of my vegetable garden, I have some bigger flower beds,” Storlien said. “And the reason being, a lot of times, diverse flowers nearby can benefit from bringing in a lot of different pollinators, which are really important for a lot of our insect-pollinated crops, like cucumbers, pumpkin and squash.”

Something that both saves space and positively impacts soil health is succession planting, a practice Storlien has also implemented in his garden.

“There are lots of ways to take quick-growing, short-season crops and grow them in the same bed as longer-growing, later-maturing crops,” he said. … “Some of the popular approaches are planting things like lettuce, spinach and basil kind of in the early part of the season, and then transplanting my peppers or my tomatoes later in the same bed as those early crops begin to kind of fill out and mature.”

Storlien said this method of planting not only reduces the need for a larger garden space but also helps keep living roots in the soil for longer and prevent the growth of weeds. Interplanting crops with different growing speeds can also serve as a marker for gardeners, such as with radishes and carrots.

“Radishes are very quick to germinate, and they can reach maturity in like 30-40 days, and carrots are notoriously slow growers; some people wonder if they’re ever going to germinate,” Storlien said. “Carrots will only be small seedlings basically by the time the radishes are harvested. The radishes essentially mark the row where the carrots were planted, which, in logistical terms, is really helpful for weeding because if those carrots aren’t up yet and you’re trying to weed, you’re like, ‘Oh, man, where’s that row?’”

Storlien said it is important for gardeners to remember that, like with most successful gardening ventures, research is as important as getting those hands in the dirt.

“Not all plants grow well together,” Storlien said. “Some combinations can actually compete or inhibit the growth of others. So, … be sure to use resources like planting guides — both the University of Minnesota and University of Wisconsin Extension sites have multiple articles and guides for people on companion planting. I always encourage folks to check them out, learn more and be inspired to find companions that work well in your garden.”