Companion Planting in the Vegetable Garden

by Jim Binnings, Collin County Master Gardener

Companion planting is basically the close planting of different plants that enhance each other's growth or protect each other from pests. As a vegetable gardener we have all heard about planting marigolds in with your vegetables. There is a lot of evidence that marigolds attract pollinators, beneficial insects, and even repel harmful pests. And they add a nice splash of color to the garden too. What we are doing by adding companion plants to our gardens is adding a little biodiversity to the garden. If you observe how nature works, we see there are relationships which exist in a natural setting such as a healthy forest or native prairie. There is a diversity of plants which attracts a diversity of insects. And the diversity of insects attracts a diversity of other creatures (such as birds) which feed off of the insects. In nature, all of these relationships over time create an ecosystem which will to a large degree be able to maintain itself. Adding companion plants to our gardens is a way of mimicking nature in a small way by adding a little biodiversity. 

 The folks at The Farmer’s Almanac have created a guide for companion gardening. In this guide they suggest that there are seven main benefits to companion gardening. They are:

1. Deterring pests: Certain plants act as insect repellents or deter critters. For example, garlic’s smell is unappealing to many pests.
2. Attracting beneficials: Some plants also attract beneficial insects. For example, borage attracting pollinating bees and tiny pest-eating wasps.
3. Shade regulation: Large plants provide shade for smaller plants in need of sun protection. For example, corn shades lettuce.
4. Natural supports: Tall plants, like corn and sunflowers, can support lower-growing, sprawling crops such as cucumbers and peas.
5. Improved plant health: When one plant absorbs certain substances from the soil, it may change the soil biochemistry in favor of nearby plants.
6. Improving soil fertility: Some crops, like beans, peas, and other legumes, help to make nitrogen more available in the soil. Similarly, plants with long taproots, like burdock, bring up nutrients from deep in the soil, enriching the topsoil to the benefit of shallow-rooted plants.  
7. Weed suppression: Planting sprawling crops like potatoes with tall, upright plants minimizes open areas, where weeds typically take hold.

For the gardeners who work at companion gardening there is a big benefit not listed above. If you consistently work at companion gardening, the garden will become more organic. The garden will need fewer chemicals to add nutrients and to control pests because a balance is starting to occur as nature works its magic. This is really appealing to me because I think we are too quick to look to chemicals to solve our garden problems.

If you want to start early in the year and bring insects into your garden plant hardy cool season annuals in early spring. You may have to start your plants from seed. Many of these plants won’t make it to your local nursery until mid-spring and that is really too late for you to get the companion plant benefits you are hoping for. As soon as the weather heats up these plants will not do well and you will end up wishing you had grown something different. All that being said, pick a plant that interests you and do the research. Examples of cool season companion annuals are sweet peas, snapdragons, marigolds, bee balm, poppies, and dill.

If warm season companion planting is more to your liking, plant these annuals when the soil has warmed up. These annuals will underperform if planted when the soil is still on the cool side and you won’t get the companion plant benefits you are hoping for. One good thing about warm season annuals is that you may be able to find many of them at your local nursery. Some warm season annuals like zinnias and sunflowers will need to be started from seed. But if the soil is warm, spread the seed around in your garden and the annuals will come up quickly. Again, pick a plant that interests you and do the research. Examples of warm season companion annuals are zinnias, sunflowers, celosia, giant marigolds, cosmos, and basil.  

One idea I read about and like is succession companion gardening. Simply put have a place in your garden for both cool and warm season companion plants. And as the cool season annual is blooming you start your warm season annual. When the cool season annual dies back, the warm season annual starts to bloom.  

As I read more about companion gardening, I realized that companion gardening has become quite sophisticated. Two books I looked at took companion gardening to a year around activity. While most vegetable gardeners focus on spring and summer gardens, under this expanded form of companion gardening fall and winter planting now become important times for maintaining and improving biodiversity in a garden. In the fall, cover crops are planted and they overwinter and help add valuable nutrients back to the soil. Cover crops like crimson clover will also attract insects who need food in the colder months. 

We here in north Texas have mild winters and can usually garden until mid-November when on average we get our first freeze. We can have a fall garden and start planting the cover crops to overwinter in January, February, and March. 

Another part of this expanded form of companion gardening and creating biodiversity is adding a few beds around the vegetable garden and planting flowers and other plants to attract insects and create habitat.

I know you might be thinking “rein in the enthusiasm fellow.” I just want to add a few flowers here and there during spring and summer to deter pests, attract pollinators, and maybe add some color to my garden. Ok, point taken. While you may not want to add extra beds, plant cover crops, and garden year around, you can certainly improve your spring, summer, and your fall garden (if you chose) by adding some companion plants and add a little biodiversity to your garden. You could add a few herbs like basil and dill. Also add a few flowers like snapdragons, marigolds, zinnias, and cosmos to your garden. These plants will attract some insects and deter others. The added variety of plants might also confuse some insects who are looking for their personal favorite vegetable to snack on.  

There are many books and articles on companion gardening but I am listing the ones I have found to give you a starting point. They are “Great Garden Companions by Sally J Cunningham and “Vegetables Love Flowers: Companion Planting for Beauty and Bounty” by Lisa M Zielger. I am also including the link to the Farmer’s Almanac companion planting guide-vegetables. It is https://www.almanac.com/companion-planting-guide-vegetables.