A good companion plant for tomatoes is basil. Basil helps improve the flavor of tomatoes, repel pests such as aphids and hornworms, and attracts pollinators such as bees. A couple of other common companion plant combinations that work well in New England are:
1. Carrots and peas: Planting carrots with peas can help improve soil fertility, as peas fix nitrogen in the soil, providing nutrients for carrot growth. Plus, their different root structures mean they won’t compete for space.
2. Marigolds and pretty much any vegetable: Marigolds are a versatile companion plant that helps to repel various pests, including nematodes, which can damage the roots of vegetable plants. They can be planted in close proximity to most vegetables, such as beans, squash, and cucumbers, among others.
3. Lettuce and onions: Lettuce and onions make good companions because they have complementary growth habits. Onions can repel aphids and other pests that can affect lettuce, while lettuce provides ground cover that helps to keep onion roots cool and moist.
4. Beans and corn: When grown together, beans provide nitrogen to the soil, which corn needs to grow strong and healthy stalks. The corn stalks, in turn, provide support for the bean vines to climb. This combination is commonly referred to as the “Three Sisters” method when combined with squash, which serves as a ground cover to reduce weed growth and maintain soil moisture.