Companion Planting: Tips and Guidelines for Growing Plants Together

Key Insights

The health and productivity of your vegetable plants may hinge on an unexpected factor: their surrounding neighbors.

A vegetable garden resembles a forest in many ways. Beneath the surface, roots intertwine and form intricate networks, linking plants to their neighbors. When you design your garden thoughtfully, certain plants can keep pests at bay, herbs can enhance the flavors of vegetables, and overall productivity can increase. However, placing incompatible plants together might hinder growth.

This technique, known as companion planting, has been practiced for thousands of years. By following these guidelines, you can encourage your plants to thrive together — and avoid pairing plants that should not coexist — helping you get the best results from your garden.

The Science Behind Companion Planting

Understanding which plants benefit each other and which don’t is rooted in traditional gardening knowledge — and is supported by science. Plants interact with soil and pests in unique ways, which is why certain combinations work. For example, plants like leafy greens, lettuce, and Brussels sprouts require more nitrogen than others.

There are various methods to enrich the soil with nitrogen, but companion planting offers a natural solution. Nitrogen-fixers like peas and beans actually restore nitrogen to the soil. One fundamental rule of companion planting is to pair nitrogen-hungry plants with nitrogen-fixing plants for optimal growth.

Herbal remedies are one of the most effective ways to combat pests. Many herbs naturally repel insects that damage vegetable plants while also attracting beneficial predators and pollinators. Among the best options are umbelliferous plants, such as dill, cilantro, and parsley, which produce small flowers in clusters on short stems. These plants attract ladybugs and wasps, which are key predators of pests like aphids and cabbage moths that harm vegetables.

The Three Sisters

One of the earliest and most renowned examples of companion planting comes from the Iroquois, who called it "the three sisters": corn, beans, and squash. These were among the first crops domesticated in North America. Corn was a staple food source, and the Iroquois believed it needed to grow in a "community" rather than in isolation.

These three plants form a perfect partnership. The tall cornstalk acts as a natural trellis for the bean vines to climb. The squash plants spread their leaves and shallow roots around the base of the corn and beans, smothering weeds and providing soil shade. The beans enrich the soil by adding nitrogen, benefiting the squash in return.

Salsa Partners

Some vegetables and herbs seem to have a natural synergy, and this is especially true for tomatoes, basil, peppers, and parsley. Essentially, these are the core ingredients for making salsa!

This is a quintessential example of companion planting, where each plant benefits the others. Basil helps keep pests like tomato hornworms and aphids at bay, while parsley draws in parasitic wasps and ladybugs. When basil is grown near tomatoes and peppers, it enhances their growth, and tomato plants with basil nearby tend to yield more fruit.

Peppers and tomatoes gain extra flavor when grown alongside basil and parsley. And of course, the best part is that these four ingredients blend beautifully together on the plate.

Flowery Friends

Certain varieties of flowers are universally excellent companion plants, while also adding a burst of color to your garden. Nasturtiums and marigolds, with their vibrant yellow, pink, orange, and red blooms, are both fantastic natural pest deterrents.

Marigolds are particularly effective at keeping deer and rabbits away from your veggies, as they find the scent of the flowers unappealing.

Nasturtiums also aid in pest control, but in a different manner. Pests like aphids and cabbage moths are drawn to these flowering plants, which works to your advantage by diverting them from your vegetables. These pests are more likely to target the sacrificial nasturtiums, so be sure to plant them nearby — but not too close — to crops like tomatoes, kale, cauliflower, and broccoli.

Squashes for Shade

If you've ever cultivated zucchini or summer squash, you know how by midsummer these plants take up a lot of space in the garden with their thick stems and broad leaves. You can make use of the shade they cast by planting greens like spinach, which typically struggle with the heat and intense sun of high summer, underneath the squash's shadow.

However, be cautious about what you plant near your zucchini and squash. Some vegetables, like pumpkin, can cross-pollinate with zucchini or squash and interfere with their growth and production for the remainder of the season.

Avoiding the Alliums

While there are numerous plants that thrive as companions to members of the allium family — such as onions, garlic, scallions, and chives — there are times when they make poor neighbors.

Beans and most other legumes can have their growth stunted if planted too near garlic. The same issue affects strawberries. Parsley and sage can inhibit garlic's growth, and garlic and asparagus aren't a great match either: garlic can hinder the growth of asparagus shoots, while asparagus can alter the flavor of garlic.

Onions don't get along with legumes. While they possess natural antiseptic properties that are great for fighting colds, they can harm the beneficial bacteria that help the roots of beans and peas thrive.

Alliums also struggle when planted alongside their own kind. With several pests that specifically target alliums, clustering them too closely can easily lead to the spread of infections or infestations.