Friends with Benefits - Companion Planting

Friends with Benefits - Companion Planting

My grandmother always had cut flowers in vases around her home. She also had a wonderful vegetable garden. As a kid, I would help her harvest, and now and then, when we would see a bug, I’d start to smash it but she would promptly stop me. "Do you know the name of that bug?" she’d ask. If I didn’t, she would first tell me to find it in her "bug book" because it might be a "good bug."

I have since learned that most of those bugs in her garden were indeed good, and most of them were there because of how she planted her garden, which was so different from other gardens in the area. In each carefully cultivated row, she had many kinds of vegetables and flowers growing side by side easily as companion plants.

What Is Companion Planting?

According to ATTRA (Sustainable Agriculture Program), companion planting can be described as "establishing two or more plant species in close proximity for some cultural benefit…[it] is thought of as a small-scale gardening practice"(1).

However, the term is applied broadly to include applications to commercial horticultural and agronomic crops.

Companion planting has a long history, but the mechanisms of how plant interactions work still need to be completely understood. Botanists and agronomists study plant interactions but seldom use the phrase “companion planting”.

Agronomists use terms like trap cropping, nitrogen fixation, weed suppression, biochemical pest suppression, and others – but they are all aspects of companion planting.

Using legumes as cover crops in a field with a heavy-feeding crop such as corn is companion planting. Planting flowers in a vegetable garden is also companion planting. Agronomists prefer to use “intercropping” to describe companion planting systems. So, if your agronomist talks about intercropping, they are talking about the age-old practice of companion planting.

Benefits Of Companion Planting For My Crops

One aspect of companion planting is planting different crops to maximize growth. My grandmother had learned from her mother, who had learned from her mother…

…that if you planted flowers with the vegetables, you got higher yields. You also gave the good bugs a place to hang out while digesting their last meal of nasty bugs. But it is more complicated than that. The benefits of good companion planting also include the following:

  • Pest Prevention
  • Improved soil fertility
  • Shade regulation
  • Weed control
  • Higher yields

And that’s just the tip of the iceberg. Many growers will tell you that proper companion planting will even improve the taste of their crops!

young beetroots companion planting

Origins Of Companion Planting

The Native American "Three Sisters Garden" is the companion planting example most people have heard of. The Farmer’s Almanac breaks it down so we can better understand the way these crops work together:

  • The corn offers the beans needed support.
  • The beans absorb nitrogen from the air into the soil to support all three crops.
  • The sisters are held together once the beans grow upward through the squash vines to find the sunlight.
  • The squash helps to protect all three crops with its large leaves that create shade and a living mulch, keeping the soil cool and moist while diminishing weeds.
  • Because squash leaves are prickly, they deter pests such as squirrels and raccoons. 
  • All three sisters offer sustainable soil fertility and contribute to a healthy diet! (2)

The Three Sisters garden concept can work in any modern garden but it will take some trial and error to find corn that can stand up to a climbing bean. Through experience, we have discovered hybrid sweet corn stalks are too weak, but multi-colored Indian popcorn stood up well to Scarlet Runner beans. Amaranth or sunflowers planted near crops gives added diversity which helps improve soil health.

How Do Plants Keep Pests Off My Crop

Some crops will repel pests off surrounding plants just by their odor, such as onions and certain herbs. Other crops may work by attracting beneficial insects to the area. And still, other plants may just be tastier to the insect pest. For example, flea beetles can damage a crop of broccoli, cabbage, peppers, or tomatoes, but they prefer eggplant, so planting one often acts as a trap plant. This may be an issue if you like eggplant because the flea beetles will probably kill the plant.

But don’t lose all hope; there is a natural enemy for flea beetles, Microctonus vittae, a braconid wasp, that can be ordered from an insectary. Just be sure to confirm that flea beetles are the issue: a large part of pest control is knowing your bugs. An excellent reference book for this is the "Field Guide to Insects and Spiders of North America" from the National Wildlife Federation.

Not all pest problems are above ground. The damage of root-knot nematodes can cause slow-growing crops that are drought-prone, fruit or flower poorly, and have short lives. The French marigold, Tagetes patula, is effective against damaging nematodes. It produces a natural chemical that kills several types of nematodes. Marigolds are annual wherever it frosts; if you don’t like the look of the dead plant, cut it off at the soil line, the roots MUST stay in the soil to be effective. If you have good soil and the winter isn’t too harsh, the flowerheads you didn’t cut off may self-seed, so your nematode problem could become an issue of the past.

Improving Soil Fertility

When you have a diversity of plants, you will attract a diversity of soil organisms. Planting various crops provides an environment that increases beneficial insect habitat, reduces the amount of damage from an insect or disease, and increases biomass both above and below ground.

Intercropping can often act as living mulches (as in the squash in the Three Sisters garden). If you plant tall sun-loving plants, so they capture the afternoon heat and sun and short shade-loving plants in their shadows, they will all be happier. If the tall plants are tomatoes and the short plants are vining nasturtiums, weed suppression and pest management will be significantly enhanced. Tomato hornworms are partial to nasturtiums, so the flowering plant does double duty; weed suppression and trap plant.

At the end of the growing season, cut off the biomass above ground. The microbes in the soil will need the decaying root matter as food over the winter. Over the years, experts have told us to remove plant debris at the end of the season, but, according to the Noble Research Institute:

"As roots die, the entire organ becomes dinner for the microbial community along with other soil creatures like worms and insects. All these root-derived inputs are fundamental to creating and storing soil carbon and are a driving force for soil health, as increased soil carbon allows for better water infiltration and storage in pastures and fields."(3)

Companion planting, or intercropping, increases the fertility of the soil. It also increases the number and type of beneficial insects.

Companion Planting Protects From Sun And Wind

In anybody’s garden or field, there are crops that are prone to sunscald. Planting taller plants, such as sunflowers, corn, or indeterminate tomatoes, in tall cages will take some of the heat off your peppers or salad greens. Plant them on the west side because the afternoons in August can get brutal. You don’t want to have nursed your plants all season to lose them to the heat. This is also when you will be thankful you planted low-growing herbs like thyme or clover in your fields or garden. That vegetation keeps the moisture in the soil and reduces evaporation from winds.

sage, lavender and wild thyme companion planting

Wind can be very detrimental in a monoculture field or a garden with low fertility. If your crop doesn’t have a substantial root system, a strong summer wind and rain will lay it on its side. Taller plants are more susceptible to wind damage, but if the soil is fertile, their root systems will be stronger and better able to handle hard rain.

When you have a diversity of crops and have left last year’s crop roots in the soil, you have a good variety of decaying vegetative matter. This matter is creating humus underground, which will contribute to healthier plants, which will be more resistant to wind, extreme weather, and insects. Those companion plant friends may make the difference between a loss and a good crop year.

Mulching will also help soil fertility and the health of your garden. Cutting above-ground biomass and leaving it on the ground is one way to mulch; on a no-till farm, that is achieved by growing a cover crop and then crimping it.

The Role Of Companion Plants In Weed Control

Ensuring the soil is covered with vegetation is the primary way to control unwanted plants. This is where some crops we wouldn’t consider companion plants come to the forefront. We usually think of companion plants as another edible garden plant, but cover crops also make great companion plants. Seeding clover under your peppers and tomatoes keeps the ground covered, fixes nitrogen in the soil, AND attracts pollinators to increase your yield.

Some plants have allelochemicals, such as juglone from Black Walnut trees, that may negatively impact a crop. Other plant allelochemicals are positive when used to suppress weed growth in a field or garden with transplants. Rye, cut or flattened, and left on the surface of the field or garden is considered one of the best crops for weed seed suppression. When you are transplanting your tomatoes or melons in rye cover, create a hole, and plant your seedling; water, and nature will help you out a great deal.

Higher Yields With Companion Planting

When your soil is fertile, you’ve suppressed the weed seeds, and you’ve planted companions to help with pest control: everything is in place for higher yields. The last ingredient to success in this case is ensuring you have various pollinators visiting your crops.

One of the best ways to attract pollinators and create habitat for good bugs is to plant flowers with your vegetables. In Lisa Ziegler’s book Vegetables Love Flowers, she writes about when she started incorporating flowers in the family’s vegetable garden.

"…my garden filled up with pollinators and nature’s pest controls – especially welcome at a time when the number of beneficial insects in most gardens, especially bees, has been diminished by herbicide exposure and loss of habitat."

Her vegetable garden has a wide range of flowers she sells as beautiful bouquets. Those flowers bring in revenue AND are a welcome mat for pollinators and beneficial insects that pollinate the vegetables. Planting for pollinators will result in higher yields in vegetable crops adjacent to flowers. It is essential to keep deadheading the flowers or, just like vegetable plants, they will quit producing. As long as there are flowers with pollen and nectar, there will be pollinators.

Companion planting is as narrow or broad a topic as you need for your farm or garden. It can mean planting basil with a tomato plant in a pot, planting a trap plant every few plants in a garden, or sowing clover in your commercial tomato field. You will attract pollinators and beneficial insects and retain moisture in the soil. The benefits of intercropping are easily scaled from a pot to a garden to a field.

Flowers in vases create connections with the living earth. We plant unique beds for flowers, but if you look around, don’t you see flowers as companions in all environments? They are companions to trees and vegetables; even those unwanted plants in your crop fields will flower.

Why not help nature by planting companion plants that benefit your crops and create more fertile soil? It’s spring and time to go out and play in the garden. Or walk your fields. Cut a bouquet of diversity on your farm. Feel the synergy between you and those plants you have nurtured—the bonds between companions.


Cited Sources:

1. Companion Planting & Botanical Pesticides: Concepts & Resources, ATTRA, April 2016 

2. The Three Sisters: Corn, Beans, and Squash, Almanac, May 2022

3. Why Roots Matter to Soil, Plants and You, Noble Research Institute, July 2018

Posted in: Soil For Humanity, Sustainable Farming

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