What Is Companion Planting and How to Use It

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If some of your plants appear to dislike each other even more than your in-laws do, proceed as you would in either case and keep the plants separated as much as possible—by at least two or three rows in your garden. On the other hand, species that get along swimmingly can be interspersed or placed next-row to each other in what is called companion planting.

Read on to learn more about companion planting and how you can use this practice in your home garden.

What Is Companion Planting?

Companion planting is simply planning your garden in such a way that plants that can inhibit each other’s growth are kept far apart while grouping those that encourage each other’s productivity together. Keep in mind that much of the information on companion gardening is based on folklore and tradition and not necessarily proven science. However, research backs up some of these plant pairings, and don’t entirely dismiss the folklore since anything that has been passed down for generations often has the experience of many gardeners behind it. Plus, there really is nothing about companion planting that can harm your garden.

For example, the flowers of a certain plant might attract insects that pollinate the plant’s neighbors too—or even parasitize some of their pests. Therefore, there are reasons other than good vibes as to why companion plants can get along well with each other. The following are a few popularly touted benefits of growing certain plants together.

The Benefits of Companion Planting

Vegetable companion planting can allow your crops to assist each other by providing shade or improving soil, among other benefits.

Providing Shade

Sun-loving plants can provide shade for other plants that prefer to keep their cool. For example, if you sowed hardy salad greens before your last frost, you might want to try planting tomatoes around them after your last frost date, or adding pole beans just south of the lettuce rows. The shade thrown by those tall edible plants can keep the greens from overheating and bolting quickly.

Loosening Clay

Plants with tap roots, such as carrots and parsnips, can loosen up obdurate clay soils. This benefits other nearby plants—such as tomatoes and watermelons—which like to put their roots down, too.

Enriching Soil

Legumes (members of the bean family) fertilize the ground around themselves by “fixing” nitrogen in the soil. Therefore, they often are grown as a cover crop and turned under just before the garden is planted—or used as a ground cover beneath nitrogen-loving vegetables such as corn.

Providing Support and Protection

Tall plants like corn can support climbing vegetables such as pole beans. In fact, Native Americans often planted corn, beans, and squash together. In that mutually beneficial arrangement, the beans climbed the corn stalks, while the squash provided a prickly mulch for both, which helped repel raccoons from the corn.

Confusing Pests

Although some companion plants can attract welcome pollinators, others can help reduce insect populations in nearby plants by attracting those insects to themselves or fending them off with odor. For example, nasturtiums and marigolds reportedly reduce the populations of cabbage worms and squash bugs near where they are planted.

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Common Companion Planting Mistakes to Avoid

Don’t make the mistake of placing the wrong plants next to each other in your companion garden, or else your crops may suffer the consequences.

Mixing Onions and Beans

Avoid placing members of the onion family near members of the bean family. Alliums produce a compound called ajoene, which can hamper the growth of legumes.

Planting Near the Wrong Trees

Don’t grow allelopathic trees, such as black walnut or tree of heaven, near your garden. These plants make room for themselves by poisoning the ground around them against other species, so you won’t want to include them in your food forest.

Growing Fennel in the Vegetable Garden

Refrain from raising fennel near any of your garden vegetables, since it too is allelopathic and stunts the growth of other plants near it—with the exception of dill. Plant it near your dog run instead, since it reportedly repels fleas.

Raising Asters Near Carrots

Although positioning flowers among vegetables can be beneficial in some cases, always keep asters far away from carrots. Aster leafhoppers may carry a yellowing disease from one to the other.

“Seating” These Relatives Near Each Other

Avoid growing potatoes and tomatoes near each other, even though they are related. That kinship makes both of them vulnerable to early and late blight—the latter having been partially responsible for the Irish Potato Famine—which easily can be spread from one species to the other, possibly causing you to lose both crops rather than just one.

Companion Planting Chart

When reading this helpful companion gardening chart, keep in mind that the cabbage family includes plants such as broccoli, brussels sprouts, and cauliflower, while the onion family contains chives, garlic, leeks, and more.

Plant	Companions	Foes
Asparagus	basil, parsley, tomato	gladiolus, onion family, potato
Bean	cabbage, carrot, cauliflower, cucumber, summer savory	beet, gladiolus, onion family
Beet	cabbage family, onion family	pole beans
Cabbage family	aromatic herbs, beet, corn, nasturtium, onion family, spinach, sunflower	dill, fennel, pole bean, strawberry, tomato
Cantaloupe	corn, sunflower	potato
Carrot	aromatic herbs, cabbage family, lettuce, onion family, pea	dill, parsnip, radish, tomato
Celery	bean, cabbage family, nasturtium, onion family, tomato	parsnip, potato
Corn	bean, cucumber, pea, potato, pumpkin, squash	tomato
Cucumber	bean, cabbage, corn, dill, nasturtium, pea, radish, sunflower	aromatic herbs, potato
Eggplant	bean, marigold	potato
Lettuce	carrot, cucumber, onion family, radish, strawberry
Onion family	asparagus, beet, cabbage family, carrot, lettuce, strawberry, tomato	bean, pea
Parsley	asparagus, corn, tomato
Parsnip	bean, onion family, pea, pepper, potato, radish	caraway, carrot, celery
Pea	bean, carrot, corn, cucumber, radish	onion family
Pepper	basil, carrot, eggplant, onion family, tomato	fennel, kohlrabi
Potato	bean, cabbage family, corn, flax, horseradish, marigold, pea	cucumber, pumpkin, raspberry, squash, sunflower, tomato
Pumpkin	corn, marigold	potato
Radish	cucumber, lettuce, nasturtium, pea	hyssop
Spinach	strawberry
Squash	corn, marigold, nasturtium, radish
Strawberry	bean, borage, lettuce, spinach	cabbage
Tomato	basil, borage, parsley	cabbage, fennel, kohlrabi, potato
Turnip	pea	potato
Watermelon	carrot, parsnip

Final Thoughts

When planning your garden, keep in mind that a wide diversity of plants interspersed with each other helps prevent pest problems. Insects tend to look for swaths of their favorite vegetable and will likely get confused when you break those swaths into smaller clusters instead. Also, flowers and herbs planted among vegetables can attract beneficial insects, which will prey on the harmful ones.

What Is Companion Planting and How to Use It in Your Home Garden