If you’ve been wondering how companion planting can benefit your garden and want to give it a try, basil is an ideal starting point. This popular herb is best buddies with tomatoes since it wards off hornworms while beckoning pollinators. It’s also a good neighbor to other vegetable plants, shooing flies away from peppers and enhancing the flavor of lettuce leaves. Best of all, basil can help you grow a healthy carrot crop — a goal many gardeners struggle to achieve. Its main benefit is telling pests to take a hike. Plus, growing basil and carrots together is simple because they like similar growing conditions: full sun, consistent moisture, and soil that doesn’t retain excess water.

Basil’s fresh fragrance is delightful to many humans but irritating to mites and weevils that prey upon carrots. Two substances basil produces — eugenol and estragole — deter aphids that can wreak havoc. Best of all, basil’s scent helps protect your garden from armyworms, which are notorious for destroying entire fields of crops. These ravenous pests don’t stop at carrots. They’ll also decimate tomatoes, peas, cabbages, sweet potatoes, and other veggies you may be growing. 

Consider creating basil “barriers” to keep bugs out of your garden. Planting basil around the edges of your carrot patch is one way to do it. You could also encircle your whole vegetable garden with basil or install this helpful herb beside plants that are vulnerable to the insects it repels. Growing some basil in pots is smart because you can move it to areas that need more defense and bring it inside when temperatures dip below 55 degrees Fahrenheit.

Carrots are grateful for basil companions’ pest-repelling efforts. They return the favor by keeping nearby soil nice and loose, which helps basil plants’ roots stay comfortable and function optimally. According to a 2024 study that appeared in Trends in Plant Science, plants notice when their soil is becoming compacted. This triggers a set of biochemical responses that often result in stunted roots. When roots don’t develop as they should, their ability to absorb water and nutrients decreases. This compromises their health and potentially their taste.

Though basil and carrots can help each other thrive, they’re less likely to do so if they get in each other’s way. Avoid this companion planting mistake by keeping a foot of space between the two types of plants. The reason for this advice has to do with carrots’ enthusiasm for underground gymnastics. When a carrot root finds an obstacle in its path — say, a stone or a clod of dirt — it will bend to grow around it. This results in a funny-looking carrot at harvest time. Additionally, planting carrots and basil too close together can encourage them to compete for the same supply of nutrients and water. If the competition is fierce, you may get smaller carrots or blah-tasting basil. The stress of competition can also make your plants more susceptible to pathogens and pest damage.