Plant these companions directly beneath and around your tomatoes

The best plants to grow under tomatoes are basil, marigolds, carrots, parsley, and borage. These companions occupy the space tomato roots don't use, suppress weeds, and some actively repel pests that damage tomato plants. Basil and parsley grow to about 12 inches tall and won't shade your tomatoes. Marigolds and borage flower and attract pollinators. Carrots grow downward into deeper soil, so they don't compete for the same nutrients your tomato roots need.

The key is choosing plants that stay shorter than your tomato variety, won't steal water and nitrogen from the main plant, and ideally offer a benefit like pest control or improved soil. Avoid planting anything directly against the tomato stem—leave at least 6 inches of clear space around the base so air can move and disease spores don't settle on lower leaves.

Key Takeaways

  • Basil, marigolds, carrots, parsley, and borage are the most reliable companions to plant under tomatoes because they occupy different soil depths and don't compete for nutrients.
  • Keep companion plants at least 6 inches away from the tomato stem to allow air circulation and prevent fungal disease.
  • Marigolds and borage attract pollinators and beneficial insects, while basil and parsley add culinary value and may deter some pests.
  • Avoid planting tall crops, nitrogen-hungry plants, or anything in the nightshade family (peppers, eggplant, potatoes) under or near tomatoes.

Basil: the classic tomato companion

Basil grows 12 to 18 inches tall, stays bushy, and won't shade a standard indeterminate tomato. It thrives in the same warm, sunny conditions tomatoes need, so watering and feeding schedules align. Basil is also edible—you harvest leaves throughout the season while the plant continues to grow.

Some gardeners report that basil repels spider mites and whiteflies, though research on this is mixed. What is clear is that basil doesn't compete with tomatoes for water or nutrients because it has a shallow root system and prefers the top few inches of soil. Plant basil seedlings 8 to 10 inches away from the tomato stem once both are established.

Marigolds and borage for pest control and pollination

Marigolds flower prolifically and attract hoverflies and parasitic wasps—insects that prey on aphids and other tomato pests. Marigolds also release compounds into the soil that may suppress certain root diseases, though the effect is modest. They grow 12 to 24 inches depending on variety, so choose dwarf or compact types to plant under tomatoes.

Borage is a taller plant (18 to 24 inches), so it works better at the edge of the tomato bed rather than directly underneath. Its blue flowers attract bees and other pollinators, which improves fruit set on your tomatoes. Borage also has a deep taproot that brings up minerals from lower soil layers, enriching the top layer as leaves drop and decompose. Both plants self-seed readily, so deadhead spent flowers if you don't want them spreading next season.

Root vegetables: carrots and beets

Carrots and beets grow downward into soil layers your tomato roots may not fully occupy, so they don't compete for the same resources. Carrots are especially useful because they break up compacted soil as they push down, improving drainage and aeration for the tomato plant above. Plant carrot seeds directly in the soil around the tomato base, leaving 6 inches of clear space from the stem.

Beets work similarly but grow larger and may shade lower tomato leaves if planted too close. Space beets at least 12 inches from the tomato stem and thin seedlings to 4 inches apart so each plant has room to develop. Both crops mature in 60 to 80 days, so you'll harvest them before they interfere with tomato growth late in the season.

Herbs that improve soil and flavor

Parsley, cilantro, and chives all grow low (under 12 inches for parsley and cilantro, 8 inches for chives) and won't shade tomatoes. Parsley has a taproot that reaches deeper than its foliage suggests, so it pulls nutrients from lower soil and doesn't compete with tomato feeder roots. Cilantro bolts quickly in heat, so it's best in spring or fall tomato plantings. Chives spread slowly and can stay in place season after season, providing a permanent low border.

These herbs are edible and useful in the kitchen, so you get a harvest while improving your tomato bed. They also attract small beneficial insects and add visual interest to the garden. Plant them 8 to 10 inches from the tomato stem once both are growing actively.

Plants to avoid under tomatoes

Never plant other nightshade family members—peppers, eggplant, or potatoes—under or near tomatoes. They share the same pests and diseases, so proximity increases the risk of infection spreading between plants. Fennel and cabbage also inhibit tomato growth through chemical compounds they release into the soil, so keep them in a separate bed.

Avoid tall plants like corn or sunflowers that will shade your tomatoes and compete for water and nutrients. Don't plant nitrogen-hungry crops like lettuce or spinach directly under tomatoes either—they'll pull nitrogen away from the main plant during the critical fruiting phase. Onions and garlic can work in moderation but are less beneficial than basil or marigolds, so they're not the best use of limited space.

Spacing and timing for underplanting

Plant companions after your tomato seedling is established and growing actively—usually two to three weeks after transplanting. This gives the tomato a head start so it won't be outcompeted by faster-growing companions. Leave 6 inches of bare soil around the tomato stem for air circulation and to prevent disease.

For direct-seeded companions like carrots or borage, sow seeds in a circle around the tomato, keeping that 6-inch buffer. For transplanted companions like basil or parsley, set them in at the same depth they were growing in their pots. Water gently after planting and keep the soil consistently moist for the first week while roots establish.

As companions mature and you harvest them (basil leaves, carrot tops, borage flowers), the space opens up and reduces competition. By mid-summer, most underplanted crops will be harvested or past their peak, leaving the tomato plant with the full bed to itself during the heavy fruiting phase.

Frequently Asked Questions

Will planting basil under tomatoes actually keep pests away?

Basil may reduce some pest pressure, but it's not a may provide. The real benefit is that basil doesn't harm the tomato and gives you an edible crop from the same space. If pests become a problem, you'll still need to monitor and treat them separately.

Can I plant lettuce or spinach under tomatoes?

Lettuce and spinach are nitrogen-hungry and will compete with tomatoes for nutrients, especially during fruiting. They're better planted in a separate bed or in spring before tomatoes are in full production.

How close can I plant basil to the tomato stem?

Keep basil at least 6 inches away from the tomato stem to allow air to move around the lower leaves and prevent fungal disease. Closer spacing traps moisture and increases the risk of early blight or powdery mildew.

Do I need to underplant tomatoes, or is it optional?

Underplanting is optional but useful. It suppresses weeds, makes use of space that would otherwise sit empty, and some companions offer pest or pollinator benefits. If your tomato bed is crowded or you prefer a straightforward setup, you can skip it.

When should I plant companions if I'm direct-seeding tomatoes?

If you're starting tomatoes from seed directly in the garden, wait until seedlings are 4 to 6 inches tall and growing steadily before sowing companion seeds around them. This prevents the companions from outgrowing the young tomato plant.