Companion Planting: A Guide

Companion planting is the practice of planting different crops near each other that help each other grow. Depending on the pairing, the league can tackle pests, nutrient requirements, pollination needs, or maximizing space! Especially helpful for those of us with limited growing space.

Many companion planting pairings are largely anecdotal or folkloric. This does not mean that these pairings have no agricultural value - the opposite in fact! Often these practices work better or differently depending on the conditions but they are easily replicable and you can see how they perform in your own gardens. And as you collect this information, you can pass on the knowledge and widen the pool of independent information that growers have access to. While there is a lot of competing information out there, it never hurts to try something new. Further, gardens function best as ecosystems and so it makes perfect sense that companion planting is relevant!

A common companion planting practice that you may know of is the Three Sisters. This is a three-crop planting method involving corn, pole beans, and squash. This practice comes from indigenous farming practices and it’s important to note that this practice was used in Indigenous communities all over the Americas. These crops offer support to each other in a number of ways. The corn acts as a trellis for the pole beans (cutting down on your labor), and the beans (and all legumes to varying degrees) fix nitrogen. They assist with providing nitrogen to the corn which requires quite a bit of fertility to produce ears. The squash is a low-growing ground cover with large leaves that shades out weeds, preserves moisture, and protects the beans and squash from larger pests. There are clear connections in this example of how these plants work together to create a beautifully functioning polycrop.

What should I plant together?

Check out our helpful table on some common garden pairings that will help you and your garden grow successfully!

Crop	Companions	Notes
Basil	Lettuce, peppers, tomatoes, purslane	Purslane shades the soil around basil plants, keeping them cool. Basil improves the flavor of tomatoes, peppers, and lettuce.
Beans	Nasturtium, rosemary, sunflowers, corn, marigolds	Nasturtiums attract aphids away from other plants. Rosemary deters insects such as cabbage loopers, moths, and slugs for leafy greens. Sunflowers create shade for sun-stressed crops.
Beets	Onions, garlic, brassicas such as cabbage, kale, brussel sprouts, cauliflower, etc.	Onions protect against borers, mites, slugs, cutworms, and maggots. Beets add minerals to the soil and the leaves are high in magnesium which is great to add to compost or to eat!
Broccoli	Brassicas, oregano, nasturtiums	Plant brassicas together so you can protect them all at once (though there are debates on this practice). Oregano repels cabbage moths. Nasturtiums repel aphids. Aromatics deter cabbage worms.
Carrots	Chives, rosemary	Chives improve growth and flavor and rosemary repels carrot flies.
Corn	Beans, squash, sunflowers, marigolds	Sunflowers around your corn can act as a structural wall to protect against wind. Marigolds reduce nematodes over time.
Cucumbers	Dill, Nasturtium	Dill and nasturtium deter aphids and improve flavor.
Lettuce	Alliums (like onions and garlic), basil	Alliums deter pests by masking the scent of lettuce. Basil improves flavor.
Onions	Chamomile	Chamomile improves growth and flavor.
Peas	Chives, mint	Chives deter aphids. Mint improves health and flavor. Instead of planting, try sprinkling the dried leaves so they decompose and are less likely to spread disease.
Peppers	Basil, oregano	Both have protective insecticidal properties.
Potatoes	Beans, cilantro, calendula, horseradish, tansy	Beans can help produce larger tubers. Cilantro, calendula, horseradish, and tansy protect against potato beetles. Corn and potatoes are both heavy feeders. Do not plant together. Do not plant potatoes and tomatoes together as they can both get and spread early and late blight.
Radishes	Nasturtiums	Improves growth and flavor.
Winter Squash and Pumpkins	Nasturtium, oregano, calendula	Nasturtium protects against squash beetles. Oregano acts as general protection as an aromatic. Calendula deters root-knot nematodes.
Spinach	Peas, beans	Provides natural shade as it gets hotter in the summer.
Tomatoes	Monarda, calendula, basil, borage	Monarda improves health and flavor. Calendula deters pests. Borage deters tomato hornworm.

Trap Crops

Trap cropping is a useful practice, especially if you deal with a lot of a certain kind of pest or if a certain vegetable in your garden never seems to make it to maturity. It is essentially the practice of implementing super spy decoy plants to lure pests away from the main crop. Using trap crops can be a bit of work because you need to get your trap established before you’re able to rely on your main crop. The idea is to grow out a crop before the maturity of your main crop and when your trap is attacked and covered in adult bugs, larvae, and eggs, physically remove it (taking your bug friends with you) and dispose of it far away. This practice works well using radishes to trap bean beetles or flea beetles and zinnias to trap Japanese beetles. Mustards can be used for harlequin bugs. To save you the effort, it’s best to use trap crops that mature quickly, and be sure to keep your nearby main crops covered and protected with row cover or perhaps an early spray of neem oil.

Are there bad planting combos?

Yes! There are a few planting combinations you should avoid. As mentioned in the table, potatoes and corn and tomatoes and potatoes should not be planted together. These plants are simply incompatible because of their nutrient needs and disease susceptibility. Another incompatible planting combination that you’ll likely come across is planting allelopathic plants with other things. Allelopathy is the chemical inhibition of one plant by another. These are plants that release certain chemicals into the environment, most often the soil, that act as germination or growth inhibitors. A great example of this is the Black Walnut tree (Juglans nigra). These trees contain juglone, which often kills plants growing nearby, most notably nightshades such as tomatoes, peppers, potatoes, and eggplants. Some other plants that are thought to be allelopathic are goldenrod, aster, and ryegrass. Garlic and legumes should not be planted together because the garlic kills the bacteria on legume roots that help fix nitrogen. In general, though, it’s always better to focus on what does work rather than what doesn’t!

	*Article Written by: Hannah Gibbons*
	About the Author: Hannah Gibbons, an employee at Sow True Seed since 2020, has nearly a decade of experience in the agricultural industry. Their passion for environmental education and regenerative agriculture has been the cornerstone of their work, aimed at making gardening accessible to all.