Tomatoes repay a little planning around what grows beside them. Tomato plants need full sun, soil with a pH of 6.0–6.8, 24–36 inches of space and 60–85 days to reach maturity, so their neighbours need to suit the same bed and the same season. This guide lists the companions for tomatoes from our crop data, how each one is thought to help, and which close relatives to keep apart.
There are 5 companions listed for tomatoes here: basil, marigolds, carrots, onions, parsley. Companion planting is traditional garden practice rather than proven science, so benefits below are described in those terms — what gardeners have long said and done. Tomatoes are in the Solanaceae family, need high water, and are started indoors and transplanted out once the weather warms; it is tender, so frost will kill it and it should only go outside once all danger of frost has passed. Check any pairing first with the companion-planting finder.
Best companion plants for tomatoes
| Companion | Why it is grown with tomatoes |
|---|---|
| Basil | Traditionally said to improve flavour; its strong scent may confuse pests. Draws pollinators when it flowers. |
| Marigolds | Grown as a border or dotted through the bed; roots are traditionally said to discourage some soil pests, and flowers attract beneficial insects. |
| Carrots | Use a different soil layer from tomatoes, so the two rarely compete directly; roots help break up the soil. |
| Onions | Take up little space at the bed edge; strong scent is traditionally said to confuse pests that hunt by smell. |
| Parsley | Attracts beneficial insects such as hoverflies when it flowers; roots occupy a different layer. |
Basil is the classic partner for tomatoes, and it earns its place for practical reasons too. It is compact enough to fit into the gaps at the edge of the bed without competing for the space tomatoes need, and it is harvested all summer. Plant it at the sunny edge where it will not be shaded out, pinch the tips to keep it bushy, and let a few plants flower late in the season to draw in pollinators.
How companion planting works
Companion planting works through four overlapping mechanisms.
Pest confusion. Many pests find their host plant by scent. Strong-smelling companions such as onions, basil and aromatic herbs are traditionally said to mask that scent, so the pest passes by. It is a delaying effect, not a barrier.
Pollinator and beneficial-insect attraction. Several companions here flower — basil, marigolds, parsley — drawing pollinators and beneficial insects in. Let a few flower.
Nitrogen fixing. Nitrogen fixing does not apply here — none of the listed companions is a legume.
Ground cover and root layers. No companion here is a ground-cover plant, so mulch does that job instead. Deep roots beside shallow ones also compete less for water and nutrients.
None of this replaces the basics. Spacing, watering, rotation and weekly inspection matter more than any pairing.
Plants to avoid near tomatoes
The plants to keep away from tomatoes are its own relatives. Tomatoes belong to the Solanaceae family, and plants in the same family share the same pests and diseases — here, aphids, tomato hornworm, whiteflies — so problems pass easily between them and build up in the soil.
| Plant to avoid | Why |
|---|---|
| Bell Peppers | Same Solanaceae family; shares pests such as aphids, tomato hornworm, whiteflies. |
| Hot Peppers | Same Solanaceae family; shares pests such as aphids, tomato hornworm, whiteflies. |
| Eggplant | Same Solanaceae family; shares pests such as aphids, tomato hornworm, whiteflies. |
| Potatoes | Same Solanaceae family; shares pests such as aphids, tomato hornworm, whiteflies. |
Keep these relatives in a different bed and rotate the Solanaceae family to fresh ground each year. Others in the same family in our crop data include Jalapenos, Habaneros, Chili Peppers, Roma Tomatoes, Cherry Tomatoes, Heirloom Tomatoes, Russet Potatoes, Red Potatoes, Petunias.
Planting layout and spacing
Give tomatoes their full spacing of 24–36 inches between plants. Crowded tomatoes mean poor airflow, more disease and smaller harvests, and no companion plant compensates for it. Work out how many plants fit your bed with the plant-spacing calculator or the square-foot garden planner.
Plant companions in the spaces the spacing leaves, not instead of it. Low companions go in the gaps and along the bed edges; taller ones go at the north side so they do not shade the tomatoes; scented herbs go closest to the crop, dotted through the row.
Tomatoes are started indoors and transplanted out once the weather warms: sow under cover, expect germination in 7–14 days, and transplant out once the weather is right. Work backwards from your last frost date with the seed-starting calculator. Tomatoes need full sun and soil with a pH of 6.0–6.8. Water needs are high, so keep the soil consistently moist with deep, regular watering rather than a light daily sprinkle, and mulch thickly to hold moisture in. The watering calculator gives a starting point for your bed size. Expect 60–85 days from sowing to maturity.
Common problems and fixes
The pests most often reported on tomatoes are aphids, tomato hornworm, whiteflies, cutworms, blight. Companions may reduce pressure, but they do not prevent them — inspect leaf undersides and new growth weekly and act while numbers are low.
| Problem | What you see | First fix |
|---|---|---|
| Aphids | Sap-sucking insects on new growth; leaves curl. | Wash off with water; encourage ladybirds. |
| Tomato hornworm | A large green caterpillar that strips leaves fast. | Hand-pick; check leaf undersides in the evening. |
| Whiteflies | Tiny white insects that rise in a cloud when disturbed. | Yellow sticky traps; wash leaf undersides. |
| Cutworms | Caterpillars that fell seedlings by chewing stems at soil level. | Cardboard collar around each young stem. |
| Blight | Dark spots on leaves, starting low and spreading in wet weather. | Water at the base; remove affected leaves. |
Aphids
Wash them off with a strong jet of water and leave ladybirds and lacewings alone to eat them.
Tomato hornworm
Hand-pick them whenever you find them, checking leaf undersides in the evening.
Whiteflies
Put out yellow sticky traps to monitor numbers and wash leaf undersides with water.
Cutworms
Push a cardboard collar an inch into the soil around each young stem.
Blight
Water at the base, space for airflow, and remove affected leaves promptly.
Unsure what you are seeing? Try the pest-identifier helper or the plant-disease checker. Remove badly affected leaves and rotate the Solanaceae family next year.
Frequently asked questions
What is the best companion plant for tomatoes?
The most widely recommended companion is basil. Traditionally said to improve flavour; its strong scent may confuse pests. Draws pollinators when it flowers.
What should not be planted near tomatoes?
Avoid other members of the Solanaceae family, including Bell Peppers, Hot Peppers, Eggplant. They share the same pests and diseases as tomatoes, so problems move easily between them. Rotate the family to a fresh bed each season.
Can I plant tomatoes with marigolds?
Yes. Marigolds is on the companion list for tomatoes. Grown as a border or dotted through the bed; roots are traditionally said to discourage some soil pests, and flowers attract beneficial insects.
How far apart should tomatoes and their companions be planted?
Space tomatoes plants 24–36 inches apart, and put companions in the gaps, along the edges and at the ends of rows. The plant-spacing calculator works out how many plants fit your bed.
Does companion planting replace pest control?
No. It may reduce pest pressure, but it does not replace inspection, spacing, watering, rotation and good airflow. Check plants weekly and act early.