Companion plants for tomatoes

What to grow next to tomatoes, what to keep away from them, and why. Each reason is tagged by how well it’s supported.

Good companions

Basil Garden tradition
Same sun and water needs; a common pairing that attracts pollinators when it flowers.
French marigold Backed by research
Roots of Tagetes patula suppress root-knot nematodes when grown densely as a cover crop the season before.
Lettuce Practical reason
Fast crop that uses the space and shade under young tomatoes before they fill out.
Carrots Practical reason
Different root depth, so they share a bed without competing much.
Onions Practical reason
Compact, shallow roots fit around tomato bases.

Potatoes Backed by research
Same family: they share early and late blight, and potato debris can carry blight to tomatoes.
Black walnut Backed by research
Juglone from walnut roots causes tomato wilt; keep beds out of the root zone.
Fennel Garden tradition
Poor neighbour for most vegetables; grow it apart.
Sweet corn Backed by research
Corn earworm is the same insect as tomato fruitworm, so the two host each other’s pest.

Space tomatoes 24 inches apart (1 per square foot in square-foot gardening); the spacing calculator works out how many fit. For timing, see when to plant tomatoes, and the full companion planting chart compares all 16 vegetables at once.

What are the best companion plants for tomatoes?

Basil, French marigold, Lettuce, Carrots, Onions. Basil: Same sun and water needs; a common pairing that attracts pollinators when it flowers.

What should you not plant with tomatoes?

Potatoes, Black walnut, Fennel, Sweet corn. Potatoes: Same family: they share early and late blight, and potato debris can carry blight to tomatoes.