Companion plants that grow well with tomatoes
The best plants to grow alongside tomatoes are ones that either improve soil nutrients, repel pests that damage tomato plants, or use garden space without competing for water and light. Basil is the most reliable choice—it repels spider mites and whiteflies while its flavor pairs naturally with tomato dishes. Carrots grow in the loose soil tomatoes prefer and their roots go deeper, so they do not compete for nutrients at the same level. Marigolds deter nematodes (tiny soil pests that eat tomato roots) and are straightforward to grow from seed.
Other strong companions include parsley, which attracts beneficial insects; borage, which brings pollinators and deters tomato hornworms; and garlic or onions, which repel spider mites and other soft-bodied insects. Lettuce and spinach grow in the shade cast by tomato plants and mature before the tomato canopy gets too dense. Nasturtiums act as a trap crop—pests prefer them to tomatoes, so they draw damage away from your main plant.
Key Takeaways
- Basil, carrots, and marigolds are the easiest companion plants to start with because they actively help tomatoes and are straightforward to grow.
- Plant shallow-rooted herbs like parsley and borage near tomatoes to attract pollinators and beneficial insects without stealing nutrients.
- Avoid planting brassicas (cabbage, broccoli, kale) and fennel near tomatoes because they stunt tomato growth and attract different pests.
- Space companion plants so they do not shade the tomato plant's lower leaves, which need air circulation to prevent fungal disease.
Plants to keep away from tomatoes
Some plants actively harm tomato growth and should be planted elsewhere in your garden. Brassicas—cabbage, broccoli, kale, and cauliflower—release compounds that stunt tomato development and compete for the same nutrients. Fennel secretes a chemical that inhibits growth in most nearby plants, including tomatoes. Corn and potatoes are also poor neighbors because they attract the same pests as tomatoes, which means infestations spread faster.
Avoid planting tomatoes near walnut trees; the tree's roots release juglone, a toxin that kills or weakens tomato plants. Dill can attract hornworms, the same pest that devastates tomatoes. If you have limited space, it is better to leave these plants out of the tomato bed entirely and grow them in a separate area of your garden.
How to arrange companion plants around tomatoes
Plant taller companions like basil and borage on the north or west side of your tomato plant so they do not block morning sun. Tomatoes need at least six to eight hours of direct sunlight daily, and shading the lower leaves reduces air circulation, which invites fungal diseases like early blight. Shorter plants like lettuce and nasturtiums can go on the south or east side, where they will be shaded by the tomato canopy as it grows.
Space companion plants at least 12 inches away from the tomato stem to avoid root competition and allow you to water and prune without disturbing neighbors. If you are using stakes or cages, leave enough room to move around the tomato plant for harvesting and maintenance. In containers, one tomato plant with one or two shallow-rooted herbs (like basil in a 5-gallon pot) works well; more than that and roots will compete for moisture.
Timing: when to plant companions with tomatoes
Plant basil, parsley, and other herbs at the same time as your tomato transplant, or even a week or two before if you want them established. These herbs grow quickly and will be useful by the time the tomato plant is large enough to need pest protection. Carrots and lettuce can go in at the same time or slightly after, since they mature on their own schedule and do not depend on the tomato plant's growth stage.
Marigolds and nasturtiums can be direct-seeded (planted as seeds rather than transplants) around the tomato plant after the soil has warmed to at least 60°F. They germinate in 7 to 10 days and flower within 4 to 6 weeks. If you are planting in spring and frost is still possible, wait until after your last frost date to plant warm-season companions like borage and nasturtiums.
Watering and feeding companion plants
Tomatoes need consistent moisture—about 1 to 2 inches of water per week depending on heat and rainfall. Shallow-rooted herbs like basil and parsley need the same amount, so they fit naturally into the same watering schedule. Carrots and lettuce are more drought-tolerant once established, but they still benefit from the regular watering tomatoes require.
If you are using fertilizer, choose one balanced for vegetables (something like 10-10-10 nitrogen-phosphorus-potassium) and explore it according to the package directions. Basil and parsley do not need extra feeding if the soil is decent to start with. Marigolds and nasturtiums actually perform better in poor soil and may get leggy or produce fewer flowers if overfed, so skip the fertilizer for those two.
Common mistakes when planting companions with tomatoes
The most common error is planting companions too close to the tomato stem, which crowds roots and makes watering difficult. Another mistake is choosing tall companions on the sunny side of the tomato plant, which shades the leaves that need light for photosynthesis. Gardeners also sometimes plant too many companions in one spot, turning a tomato bed into a crowded mess where nothing has room to grow.
A third mistake is planting brassicas or fennel without realizing they harm tomatoes, then wondering why the tomato plant looks weak. Finally, many people plant basil or other tender herbs at the same time as tomatoes in cool spring weather, then lose them to cold nights. Wait until nighttime temperatures stay above 50°F before planting warm-season herbs.
Frequently Asked Questions
Can I plant basil and tomatoes in the same pot?
Yes, basil and tomato grow well together in a container. Use a pot at least 5 gallons for one tomato plant and one basil plant. Water when the top inch of soil feels dry, and pinch basil leaves regularly to encourage bushiness and prevent it from shading the tomato plant.
Do I need companion plants for tomatoes to grow?
No, tomatoes will grow without companions. Companion plants improve pest control and soil use, but a healthy tomato plant in good soil with proper watering and sunlight will produce fruit on its own. Companions are helpful, not required.
What if I plant tomatoes near brassicas by accident?
Move the brassicas to another bed as soon as you notice the problem. If they are already established, dig them out carefully to avoid disturbing the tomato roots. The tomato plant may recover once the brassica is gone, especially if it is still young.
Can I plant flowers next to tomatoes just for looks?
Yes, as long as they are not fennel or other plants that harm tomatoes. Nasturtiums and marigolds are both attractive and useful. Zinnias and sunflowers also look nice, though they do not offer pest control benefits—just make sure they do not shade the tomato plant's lower leaves.
How close can lettuce grow to a tomato plant?
Plant lettuce at least 12 inches away from the tomato stem. Lettuce is shallow-rooted and will not compete much, but it still needs its own space to develop. As the tomato plant grows and shades the lettuce, the lettuce will actually benefit from the cooler conditions and may last longer into summer.