Companion plants for tomatoes are a cornerstone of many thriving vegetable gardens. Tomatoes are heavy feeders and somewhat prone to pests and disease, but when planted alongside the right partners, they can grow stronger, healthier, and more prolific. Whether you're cultivating tomatoes in a backyard plot, raised beds, or containers, thoughtful companion planting can improve soil fertility, deter pests, increase yield, and enhance flavor.
This comprehensive guide explores the best and worst companion plants for tomatoes, explains the science behind these relationships, and offers actionable planting strategies to help gardeners at any level.
The Principle Behind Companion Planting for Tomatoes
Companion planting is rooted in the idea that certain plants can benefit one another when grown in proximity. While this concept has been used by farmers and gardeners for centuries, it’s now increasingly supported by research into plant biochemistry, insect behavior, and soil microbiology.
For tomatoes, companion planting is especially valuable because:
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Tomatoes are susceptible to a variety of pests (aphids, whiteflies, hornworms).
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They are heavy feeders and often need nutrient-dense soil.
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They are prone to fungal diseases, especially in humid conditions.
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Their dense foliage can shade out smaller plants, so selecting companions that tolerate partial shade or grow low to the ground is important.
By selecting plants that repel pests, attract pollinators or beneficial insects, improve soil health, or reduce disease, you can reduce dependency on chemical treatments and encourage a more balanced garden ecosystem.
Best Companion Plants for Tomatoes
Many vegetables, herbs, and flowers serve as excellent companion plants for tomatoes. These allies help in various ways, from pest control to pollination and improved flavor.
1. Basil
Basil is a classic companion for tomatoes and a favorite in culinary pairings as well. Gardeners have long observed that tomatoes grown with basil nearby tend to taste better and suffer less from pests.
Benefits:
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Repels tomato hornworms, aphids, and whiteflies.
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May improve tomato flavor and vigor.
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Attracts pollinators when in bloom.
How to Plant: Space basil around the perimeter of your tomato plants. It’s compact enough not to compete for space and thrives in similar conditions.
2. Marigolds (Tagetes spp.)
Marigolds are famous for their pest-repellent abilities. These flowers contain compounds that repel nematodes and many flying insects. Their strong scent also masks tomato aroma from pests.
Benefits:
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Deters nematodes in the soil.
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Repels aphids, whiteflies, and beetles.
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Attracts beneficial insects such as hoverflies and parasitic wasps.
How to Plant: Interplant marigolds between tomato plants or plant them as a border. French marigolds are especially effective against nematodes.
3. Garlic and Onions (Alliums)
Allium family plants like garlic, chives, and onions are strong-smelling and known for their ability to deter pests. They also have antifungal properties that may help reduce disease pressure.
Benefits:
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Repels spider mites and aphids.
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Can help reduce fungal infections in tomatoes.
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Compact enough not to compete for sunlight.
How to Plant: Plant around the base of tomato plants or in adjacent rows. Chives are especially useful in small spaces.
4. Carrots
Carrots have a small footprint above ground but work well with tomatoes as they help break up soil with their roots. The pairing is mutually beneficial, though some root stunting in carrots can occur if tomatoes are too close.
Benefits:
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Help aerate soil around tomato roots.
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Don’t compete for sunlight.
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Allow for vertical garden layering.
How to Plant: Sow carrots around the base of tomatoes or in inter-row spaces. Thin appropriately to avoid crowding.
5. Lettuce and Leafy Greens
Lettuce, arugula, and spinach grow quickly and stay low to the ground. They can be grown between tomato plants early in the season, helping to shade the soil and retain moisture.
Benefits:
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Ground cover reduces weeds and moisture loss.
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Fast-growing, so they mature before tomato plants fill out.
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Helps maximize space.
How to Plant: Plant in rows or patches between young tomato plants. Harvest before tomato canopy grows dense.
6. Calendula (Pot Marigold)
Unlike marigolds, calendula is technically in the daisy family. Still, it's a powerful companion that attracts predatory insects and traps aphids away from tomatoes.
Benefits:
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Trap crop for aphids.
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Attracts pollinators and beneficial insects.
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Long blooming season.
How to Plant: Place near the ends of tomato rows or in corners of garden beds.
7. Nasturtiums
Nasturtiums act as living traps for aphids, whiteflies, and even squash bugs. Their spreading growth habit also suppresses weeds and retains moisture.
Benefits:
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Attracts aphids away from tomatoes.
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Covers soil to retain moisture.
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Edible flowers are a bonus.
How to Plant: Let nasturtiums sprawl at the base of tomato plants or hang over the edge of raised beds.
8. Asparagus
Though a bit unconventional, asparagus and tomatoes are long-time allies in the perennial vegetable world. Tomato plants repel asparagus beetles, while asparagus helps deter nematodes that affect tomatoes.
Benefits:
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Asparagus beetle control.
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Tomato roots deter soil-borne pests in asparagus beds.
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Compatible growing seasons.
How to Plant: Plant tomatoes in the same bed as established asparagus. Keep spacing generous to prevent shading.
9. Borage
Borage is often cited as a near-universal companion plant, and tomatoes are no exception. This herb attracts pollinators and beneficial predatory insects.
Benefits:
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Attracts bees and predatory insects like lacewings.
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Improves tomato health and flavor (anecdotally).
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Adds trace minerals when used as mulch.
How to Plant: Plant borage between or near tomato rows. Be aware that it self-seeds prolifically.
Companion Plants to Avoid Near Tomatoes
Not all plants play well with tomatoes. Some can hinder growth, compete for nutrients, or attract pests and diseases.
1. Cabbage Family (Brassicas)
This includes broccoli, cauliflower, cabbage, kale, and Brussels sprouts. These plants prefer different soil pH and nutrient profiles and often compete with tomatoes for space and resources.
Why Avoid:
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Compete for nitrogen.
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Attract cabbage moths and beetles that don’t help tomatoes.
2. Corn
Corn and tomatoes share a common enemy: the tomato hornworm (also known as the corn earworm). Planting them near each other increases pest pressure.
Why Avoid:
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Both are targets of similar pests.
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High nutrient demands can stress soil fertility.
3. Potatoes
Tomatoes and potatoes are both part of the nightshade family and suffer from the same diseases, especially blight. Growing them together can accelerate the spread of fungal infections.
Why Avoid:
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Increases risk of blight and other soil-borne diseases.
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Similar pests like Colorado potato beetles.
4. Fennel
Fennel is known to inhibit the growth of many plants around it due to allelopathic compounds released by its roots.
Why Avoid:
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Releases chemicals that stunt nearby plants.
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Does not benefit tomatoes in any way.
Planning Your Tomato Garden with Companions
To make the most of companion plants for tomatoes, thoughtful garden design is essential. Here are some practical tips:
Garden Layout Ideas
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Circle Design: Tomato in the center, surrounded by basil, chives, or marigolds.
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Border Method: Tomatoes in rows with borders of beneficial herbs and flowers.
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Interplanting: Place lettuce or carrots between tomato plants in raised beds.
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Vertical Integration: Grow climbing nasturtiums or vining borage on trellises next to indeterminate tomatoes.
Timing Considerations
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Start leafy greens and fast-maturing crops like radishes early in the season.
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Interplant herbs like basil and chives once tomatoes are established.
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Add flowers like marigolds and nasturtiums after transplanting tomato seedlings to avoid crowding during early growth.
Maintenance Tips
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Regularly prune lower tomato leaves to increase airflow and reduce disease.
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Use mulch around tomato bases to reduce soil splash (a common source of blight).
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Rotate tomato planting areas yearly to reduce disease buildup in soil.
Companion Planting in Containers
Tomatoes also thrive in containers, and companion planting can still apply on a smaller scale. In a large pot:
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Plant one tomato plant in the center.
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Surround it with basil or chives.
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Use trailing herbs like thyme or nasturtiums to drape over the edges.
This strategy saves space, looks attractive, and boosts plant health.
Benefits Beyond Pest Control
While much of the focus is on pest management, companion plants for tomatoes offer other key advantages:
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Pollination Support: Flowers like borage and calendula attract pollinators to the garden, which helps tomato fruit set.
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Biodiversity: A more diverse garden is naturally more resilient to disease and pest outbreaks.
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Soil Health: Legumes and root crops improve soil texture and add organic matter over time.
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Space Optimization: Layered planting increases food output in small garden spaces.
Final Thoughts on Companion Plants for Tomatoes
Companion planting is not a gimmick—it’s a time-tested strategy for cultivating healthier tomatoes with fewer problems. By choosing the right partners, you can build a mini ecosystem where your tomato plants flourish, pests stay away, and soil stays fertile. Whether you’re adding herbs like basil and chives, flowers like marigolds and nasturtiums, or practical vegetables like carrots and leafy greens, each companion brings something valuable to your tomato patch.
Avoid incompatible plants like potatoes, corn, and brassicas, and always consider spacing, timing, and maintenance. With a little planning and a diverse selection of companions, your tomato garden can be more productive, attractive, and sustainable from the ground up.