Companion Planting: Which Vegetables Grow Better Together

This is one of the most popular companion pairings in North American home gardens, and for good reason. Basil is thought to repel aphids, spider mites, and tomato hornworm moths, though research on the mechanism is still evolving. What's well-established is that basil attracts pollinators when it flowers, which benefits the surrounding garden.

Plant basil 12–18 inches from tomato stems so both plants have adequate airflow. Pinching basil flowers early keeps the herb productive longer and slows bolting. As a bonus, you'll have both ingredients for a Caprese salad growing within arm's reach.

Developed by Indigenous farmers in North America over centuries, the Three Sisters system is one of the most ecologically integrated planting strategies in traditional agriculture. Corn provides a vertical trellis for pole beans to climb. Beans fix atmospheric nitrogen into the soil, feeding the heavy-feeding corn and squash. Squash sprawls along the ground, shading out weeds and retaining soil moisture with its broad leaves.

Plant corn first and allow it to reach 4–6 inches before introducing beans and squash. Space the corn in blocks rather than single rows to ensure adequate pollination. This system works best in larger garden spaces where the squash has room to spread.

Carrots and onions are frequently cited as mutual pest deterrents. The strong scent of onions is thought to confuse carrot flies, while carrots may help mask onions from onion flies. Neither effect is absolute, but the pairing is space-efficient and causes no documented harm between the two crops.

Both plants are relatively shallow-rooted and can be interplanted in rows without competing excessively for nutrients. Thin carrots early so root development isn't crowded. This pairing is a practical way to double the productivity of a single bed without overcomplicating your layout.

Dill is a powerhouse companion herb. It attracts beneficial insects — including parasitic wasps that prey on aphids and caterpillars — and pollinators that cucumbers need to set fruit. Young dill planted near cucumbers supports both goals effectively.

One important caveat: mature dill that has gone to flower and begun setting seed can actually inhibit cucumber growth. Keep dill trimmed or stagger plantings so the dill doesn't outpace the cucumbers. Harvest dill regularly to keep it in a productive, pre-flowering state through the season.

Brassicas — including cabbage, broccoli, kale, and Brussels sprouts — are notoriously attractive to cabbage moths and aphids. French marigolds (Tagetes patula) are widely used around brassicas as a deterrent. Their scent is believed to confuse pests, and their roots produce a compound that suppresses certain soil nematodes.

Plant marigolds around the perimeter of your brassica patch or interplant them throughout. They require minimal care and bloom prolifically through summer. As an added benefit, marigolds attract pollinators and beneficial predatory insects that help manage garden pests more broadly.

Lettuce bolts — goes to seed and turns bitter — quickly in summer heat. Planting it in the partial shade cast by taller crops like staked tomatoes, trellised cucumbers, or corn can extend the productive window of your lettuce into warmer months.

This is a space-stacking strategy as much as a traditional companion planting technique. The taller plant uses vertical space while lettuce occupies the cooler ground-level zone beneath it. Time your lettuce succession plantings so you're harvesting before heat becomes intense, and use the tall-crop shade to buy a few extra productive weeks.

Companion planting isn't only about helpful pairings — knowing what not to plant together is equally important. Fennel is one of the most problematic plants in a mixed vegetable garden. It releases allelopathic compounds (natural chemicals that inhibit growth in neighboring plants) that can suppress tomatoes, peppers, beans, and most other vegetables.

Keep fennel isolated in its own container or a separate bed at least several feet from your main vegetable garden. Similarly, avoid planting onions near beans and peas, as alliums can stunt legume growth. And keep brassicas away from strawberries, which compete poorly alongside heavy feeders in the same soil space.