Companion plants help tomatoes thrive and keep pests away

Planting certain vegetables, herbs, and flowers near tomatoes improves their growth, reduces pest damage, and makes better use of your garden space. Some plants repel insects that harm tomatoes. Others improve soil quality or attract beneficial insects that eat tomato pests. A few straightforward grow well in the same conditions without competing for water and nutrients.

The plants that work best near tomatoes fall into three groups: herbs that repel pests, vegetables that don't compete for resources, and flowers that attract helpful insects. You don't need to plant all of them—even one or two companions will make a difference.

Key Takeaways

  • Basil, parsley, and marigolds planted near tomatoes reduce damage from aphids, whiteflies, and spider mites without requiring extra care.
  • Carrots, onions, and lettuce grow well alongside tomatoes because they use different soil depths and don't shade the plant.
  • Borage and nasturtiums attract bees and parasitic wasps that eat tomato hornworms and other common pests.
  • Avoid planting brassicas (cabbage, broccoli, kale) and fennel within a few feet of tomatoes, as they compete for nutrients or release chemicals that slow tomato growth.
  • Space companion plants far enough away that they don't shade your tomatoes or compete for water at the root level.

Herbs that repel tomato pests

Basil is the most reliable companion for tomatoes. It repels aphids, whiteflies, and spider mites—three of the most common tomato pests. Plant basil 12 inches away from the tomato stem. It grows quickly and you can harvest leaves for cooking throughout the season. Basil also prefers the same warm, sunny conditions as tomatoes, so it thrives in the same spot.

Parsley attracts parasitic wasps, which lay eggs inside tomato hornworms and kill them from the inside. Plant parsley 18 inches from the tomato stem. It tolerates partial shade better than basil, so it works well on the shadier side of a tomato plant. Parsley takes longer to mature than basil but produces leaves for months once established.

Chives repel aphids and spider mites with their onion-like smell. They spread slowly and won't crowd out tomatoes. Plant them 12 to 18 inches away. Chives come back year after year in most climates, so they're a low-maintenance choice.

Flowers that attract beneficial insects

Marigolds are the most popular tomato companion flower. They repel whiteflies and spider mites directly and also attract hoverflies, whose larvae eat aphids. Plant marigolds 12 to 18 inches from the tomato stem. They bloom all season in full sun and require little water once established. Marigolds also tolerate poor soil, so they work in garden corners where tomatoes wouldn't thrive.

Borage attracts bees and parasitic wasps. The wasps lay eggs in tomato hornworms and other large pests. Borage grows tall—up to 2 feet—so plant it on the north side of tomatoes where it won't shade them. Space it at least 2 feet away. Borage self-seeds, so you may have volunteers next year.

Nasturtiums act as a trap crop: pests prefer them to tomatoes, so they concentrate on the nasturtiums instead. Plant them 18 to 24 inches away. Nasturtiums also attract hoverflies and parasitic wasps. They tolerate partial shade and poor soil, making them useful in less-ideal garden spots.

Vegetables that grow well in tomato beds

Carrots grow in the loose soil around tomato roots without competing. Their roots go deep while tomato roots stay in the upper 12 to 18 inches. Plant carrots 6 to 12 inches away from the tomato stem. They take 60 to 80 days to mature, so you can harvest them before or after the tomato season depending on when you plant.

Onions and garlic repel spider mites and some fungal diseases. They also use different soil nutrients than tomatoes. Plant them 12 inches away. Both tolerate the same watering schedule as tomatoes and don't need extra fertilizer. Garlic is planted in fall and harvested in early summer, so it's often gone before tomatoes reach full size.

Lettuce and spinach grow in the shade cast by tomato plants once they reach full height. Plant them at the base of the tomato, 6 to 12 inches away. They mature in 30 to 50 days, so you harvest them early in the season before the tomato canopy gets too dense. This makes efficient use of space in a small garden.

Peppers grow well next to tomatoes because they prefer the same temperature, sunlight, and watering schedule. Plant them at least 18 inches apart so air circulates between them and reduces fungal disease. Peppers don't repel pests or improve soil, but they won't harm tomatoes either.

Plants to keep away from tomatoes

Brassicas—cabbage, broccoli, kale, and cauliflower—compete with tomatoes for nitrogen and potassium. Plant them at least 3 feet away, or better yet, in a separate bed. If space is tight, plant brassicas earlier in the season and harvest them before tomatoes reach full size.

Fennel releases a chemical that slows the growth of many plants, including tomatoes. Keep fennel out of the tomato bed entirely. If you want to grow fennel, plant it in a container or a separate area of the garden at least 5 feet away.

Corn competes for water and nutrients and can shade tomatoes if planted on the south or west side. If you grow both, plant corn at least 4 feet away and on the north side where it won't block sun.

How to arrange companion plants in your garden

Space herbs and flowers 12 to 18 inches from the tomato stem. This keeps them close enough to repel pests or attract beneficial insects, but far enough away that they don't shade the plant or compete for water at the root level. If you're growing multiple tomatoes in a row, plant companions between them rather than in a separate area—pests move along the row, so companions scattered throughout offer better protection.

Plant tall companions like borage on the north side of tomatoes so they don't cast afternoon shade. Plant low-growing companions like lettuce and chives on the south and east sides where they benefit from reflected heat and don't block sun. This arrangement also improves air circulation, which reduces fungal disease.

Water companions and tomatoes on the same schedule—deeply once or twice a week rather than daily shallow watering. This keeps roots healthy and reduces disease. If a companion plant needs different watering (like basil, which prefers slightly moister soil), plant it in a container next to the tomato bed instead of directly in the ground.

Frequently Asked Questions

Can I plant basil and marigolds together near the same tomato?

Yes. Plant basil 12 inches from the stem and marigolds 12 to 18 inches away on a different side. They don't compete and both repel common pests. This combination gives you the most pest protection in a small space.

What if I don't have room for companion plants?

Plant basil in a pot next to the tomato bed. A single potted basil plant repels aphids and whiteflies over a 3- to 4-foot radius. You can also grow marigolds in containers and move them around the garden where pests appear.

Do companion plants work if I use pesticides?

Pesticides kill the beneficial insects that companion plants attract, so they reduce the benefit. If you spray for pests, space companions farther away and focus on herbs like basil that repel pests directly rather than flowers that attract helpful insects.

When should I plant companions—at the same time as tomatoes?

Plant herbs like basil and chives at the same time as tomatoes, since they grow at similar speed. Plant flowers like marigolds and nasturtiums 2 to 3 weeks after tomatoes so they don't shade seedlings. Plant lettuce and spinach after tomatoes are established and 12 inches tall.

Will companion plants reduce my tomato yield?

No. Properly spaced companions improve yield by reducing pest damage and disease. They use different soil depths or nutrients, so they don't compete. In fact, gardens with companions often produce more tomatoes than gardens with tomatoes alone.