What Should I Plant Next to Tomatoes?

Tomatoes are hungry, tall, and attractive to a wide range of pests — which makes choosing their neighbours one of the most important decisions in a kitchen garden. The right companions can reduce aphid pressure, deter nematodes in the soil, attract the insects that pollinate your flowers, and make better use of the space around your plants. The wrong ones compete for nutrients or share diseases. Here is what actually works.

Basil — the Classic Tomato Partner

Basil and tomatoes are planted together so often that gardeners assume it must work, and largely it does. Basil's aromatic volatile oils appear to repel thrips and aphids when planted in dense clusters around the base of tomato plants. Some growers also report improved fruit flavour near basil, though the mechanism for this is less clear. Grow basil in 30 cm clumps every metre along the tomato row rather than as scattered single plants — concentration matters.

French Marigolds for Nematode Control

French marigolds (Tagetes patula) produce a substance called alpha-terthienyl in their roots that is toxic to root-knot nematodes — tiny soil-dwelling worms that cause knobby, stunted root growth. This is one of the best-documented benefits in all of companion planting. For it to work you need to plant marigolds densely across the full bed in the season before your tomatoes go in, or interplant them thickly throughout the season. A border of a few plants will not have the same effect.

Borage for Pollination and Pest Pressure

Borage is one of the most pollinator-attractive plants you can grow. Its star-shaped blue flowers draw bumblebees and hoverflies that will move on to pollinate your tomato flowers. Hoverfly larvae are also voracious aphid predators. Borage self-seeds freely, so plant it once and it will return year after year. Allow it to grow tall at the ends of your tomato rows where it will not shade the crop.

What to Keep Away from Tomatoes

Fennel is the most important plant to keep well away from tomatoes. It releases root chemicals that inhibit the growth of most vegetables, and tomatoes are particularly sensitive. Keep fennel in its own isolated bed. Brassicas and tomatoes do not make good neighbours — they compete for similar nutrients and both attract aphids that can move freely between them. Corn planted very close can create excessive shade and increases the risk of tomato hornworm populations because the moths that lay hornworm eggs are attracted to both crops.

Good Space-Fillers Around Tomatoes

Lettuce and spinach thrive in the dappled shade at the base of tall tomato plants during summer. They benefit from the shelter, and their shallow roots do not compete with the deeper tomato root system. Parsley sown around the base of tomato plants attracts predatory wasps. Garlic interplanted in the row has some evidence for reducing spider mite populations, particularly in greenhouse growing situations.