This One Tasty Plant Can Increase Your Tomato Yield By 20%, and it’s So Easy to Grow From Seed

Companion planting when growing vegetables isn’t just based on folklore passed down through generations: recent studies show some classic combinations work in ways we never imagined possible. Take tomatoes and basil. They’re not only best friends in the kitchen, but incredible allies in the veggie patch, and studies now explain the science behind why growing basil alongside your tomatoes really does increase the yield by as much as 20%.

Intercropping and companion plant research is being led by the agricultural industry as a response to the increasingly problematic practice of growing single crops as monocultures, where abundant harvests rely on the use of pesticides and fertilizers. About 200 million metric tonnes of tomatoes are commercially produced around the world every year, so you can understand why this crop has attracted plenty of attention from the scientific world. One of the most significant findings is that superhero basil is one of the best companion plants for tomatoes – and we gardeners growing crops at home can enjoy the benefits, too.

So, once you've decided the best tomatoes for you to grow this summer, it’s now a given that you should plant basil alongside. Here’s why.

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1. Basil Makes Tomato Plants Respond Faster to Stress

Recent studies show that basil releases volatile compounds that prime a tomato plant’s defense mechanisms. So, if a tomato plant is attacked and damaged by pests or disease, one that's growing alongside basil will react more quickly and robustly than one that isn't. Tomato plants are vulnerable to all sorts of pests and diseases, so strengthening the stress response is an across-the-board benefit, because healthy plants grow more fruit.

If you're wondering how to increase tomato yield, you should sow basil as a companion plant for this reason alone.

2. Basil Helps Tomato Plants Grow Stronger Roots

The preliminary findings of a 2024 study showed that planting basil significantly increased the symbiosis of mycorrhizal fungi in tomato plant roots. Mycorrhizal fungi are beneficial microorganisms that form a symbiotic relationship with roots and improve their ability to absorb water and nutrients.

This doesn’t just make for stronger, healthier plants, but ones that can tolerate drought and extreme environmental conditions better. In the face of this year's predicted super El Niño event, it makes more sense than ever to grow resilient plants.

3. Basil Blooms Attract Pollinators

A tomato flower needs to be pollinated before a fruit can form. Pollination can be done naturally by bees or the wind, or by us gardeners giving the plants a gentle shake; some folk hold an electric toothbrush to a flower stem for a few seconds to mimic the buzzing of bees and trigger pollen release!

Plant some basil and let it bloom, however, and it will attract plenty of bees to ensure thorough pollination. It's a common issue with homegrown tomatoes that only the lower half of a truss fruits while the later flowers don’t set, and this will solve that problem. One study found that the average number of fruits per cluster on tomatoes grown by themselves was 5.88, compared to 7.2 fruits per cluster on plants grown with basil.

We normally pinch off the flowerbuds to prevent basil leaves becoming bitter and tough, but leaving some to bloom will also give you edible flowers and seed to save for next year’s sowings.

4. Basil Helps Control Tomato Pests

Leaving basil to flower will also attract ladybugs, which will help to control aphids. Basil’s strong fragrance will also help general pest control, masking the scent of the tomato plants so fewer aphids arrive in the first place. The powerful smell of basil’s aromatic oils also confuses whiteflies and tomato hornworms.

And the less energy your tomato plant has to put into dealing with these stressors, the more energy it has to grow fruit.

5. Tomatoes Grown With Basil Taste Better

This supposition has long been bandied about in the gardening world, but a study by the University of Florida concluded that tomatoes grown with lemon basil were indeed tastier than ones grown without. We know that aroma contributes significantly to flavor perception, but whether the tomatoes actually tasted better or the research volunteers simply perceived them as more flavorful as a result of the basil’s scent is a moot point. Delicious tomatoes are delicious tomatoes!

How to Grow Basil With Tomatoes

Because basil plants have shallow roots, they won’t negatively impact the growing conditions of your tomatoes. Both need similar conditions of consistent moisture, well-drained soil and 6–8 hours of sunlight a day, so they’ll thrive together. Space basil 10–20 inches from the tomato plant for optimum protection without congestion.

Leave a few basil plants to flower, but keep picking leaves and pinching off flowerbuds and stem tips from the rest to encourage strong, bushy, fresh and aromatic growth. Harvest no more than a third of a plant’s leaves at a time.

Most types of basil are short-lived perennials but won’t survive temperatures below freezing, so are best treated as annuals in all zones. Collect seed in late summer to re-sow the following year once soil temperatures have reached 70°F.

The Best Basil Varieties to Grow With Tomatoes

The latest estimates suggest there are as many as 150 types of basil but as this species cross-breeds so easily, it’s impossible to know for sure! These are the types considered most effective as companion plants for tomatoes. It’s likely that different varieties may each work more efficiently in the many ways basil supports a heavy yield so, until we know more, it’s probably best to plant a few different varieties with your tomatoes.

Sweet Basil

Ocimum basilicum is the basil most often used as a companion plant for tomatoes. Also often referred to as common basil, it’s grown as an annual in zones 3–10, inside and out. It’s fast-growing and has a sweet and slightly peppery flavor. Seeds are available from Eden Brothers, and seeds and plants are stocked by Burpee.

Genovese Basil

A variety of sweet basil Ocimum basilicum, Genovese has a similar sweet anise flavor but larger leaves, and is considered the go-to for making pesto. It’s also fast-growing, raised as an annual in zones 3–10, inside and out. Seeds are available from Eden Brothers, Burpee and Botanical Interests.

Italian Large Leaf Basil

Also a sweet Ocimum basilicum variety and similar to Genovese, this has even bigger leaves, up to four inches long. Fast-growing, it's easily raised as an annual in zones 3–10, inside and out. Seeds are available from Burpee and Eden Brothers.

Purple Basil

The aroma of purple basil is more intense than regular sweet basil, so this is particularly effective at repelling pests. Its flavor is equally strong and fast-growing Ocimum basilicum var. purpurascens can be grown as an annual in zones 3–10, inside and out. Those purple leaves are pretty, too. Seeds are available from Eden Brothers.

Greek Basil

With tiny-leaved plants growing into a tidy 8-inch-high mound, Greek basil is handy for container-grown tomatoes. Ocimum minimum is the variety used in the study that found basil strengthens a tomato plant’s stress-response, too. Despite its compact size, this variety has a strong clove-anise aroma for pest-repelling purposes, and a robust flavor. This is a fast-grower raised as an annual in zones 3–10, inside and out, and seeds are available from Burpee.

Lemon Basil

While lemon basil doesn’t have the eugenol content of sweet basil that works so effectively as a pest repellent, this is the basil used in the tasty tomatoes study. As its common name suggests, Ocimum x africanum has an intense citrus aroma and taste, with just a hint of anise. Grown as an annual in zones 3–10, inside and out, seeds of this fast-growing basil are available from Botanical Interests.

And the best thing about growing basil alongside your tomatoes? You’ll be able to harvest plenty of tasty leaves to add to your bumper crop of tomatoes, for all sorts of delicious dishes.