Basil repay a little planning around what grows beside them. Basil are a tender annual herb that is the tomato bed's classic partner, grown for pesto, salads and tomato dishes. They need full sun, soil with a pH of 6.0–7.5, 12–18 inches of space and 60–70 days to reach maturity, so their neighbours need to suit the same bed and the same season. This guide lists the companions for basil from our crop data, how each one is thought to help, and which close relatives to keep apart.
There are 5 companions listed for basil here: Tomatoes, Peppers, Oregano, Marigolds and Asparagus. 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. Basil are in the Lamiaceae family, need moderate water, and are started indoors and transplanted out once the weather warms; they are tender, so frost will kill them and they should only go outside once all danger of frost has passed. Check any pairing first with the companion-planting finder.
Best companion plants for basil
| Companion | Why it is grown with basil |
|---|---|
| Tomatoes | The classic pairing: basil at the feet of tomatoes, where its scent is traditionally said to confuse pests and its flavour is said to improve. |
| Peppers | Peppers give basil a warm, sheltered spot at their feet, and basil's scent is traditionally said to help confuse pests. |
| Oregano | A low, spreading herb that covers bare soil and is traditionally said to confuse pests with its strong scent. |
| Marigolds | Grown as a border or dotted through the bed; its roots are traditionally said to discourage some soil pests, and its flowers attract beneficial insects. |
| Asparagus | A long-lived perennial bedfellow that occupies a different root zone; the herb's scent is traditionally said to help mask the bed from pests. |
Tomatoes are the first companion to reach for with basil, and it is the best-known companion herb of all, grown as much for the kitchen as for the bed it shares. It is the tall neighbour that sets the shape of the bed: stake it well, keep the lower leaves clear, and plant the herb at its sunny base where it gets light without being shaded out.
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 Oregano 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 — Marigolds — 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 basil
The plants to keep away from basil are its own relatives. Basil belong to the Lamiaceae family, and plants in the same family share the same pests and diseases — here, aphids, slugs, whiteflies — so problems pass easily between them and build up in the soil.
| Plant to avoid | Why |
|---|---|
| Mint | Same Lamiaceae family; shares pests such as aphids, slugs, whiteflies. |
| Rosemary | Same Lamiaceae family; shares pests such as aphids, slugs, whiteflies. |
| Thyme | Same Lamiaceae family; shares pests such as aphids, slugs, whiteflies. |
| Sage | Same Lamiaceae family; shares pests such as aphids, slugs, whiteflies. |
| Lavender | Same Lamiaceae family; shares pests such as aphids, slugs, whiteflies. |
Keep these relatives in a different bed and rotate the Lamiaceae family to fresh ground each year. Others in the same family in our crop data include Marjoram, Catnip.
One overlap to note: Oregano also belongs to the Lamiaceae family, so it shares some pests with basil. It stays on the companion list above because our crop data lists it as a companion of basil — gardeners still grow it together — but give it its own space, keep the bed aired, and watch it for aphids, slugs, whiteflies.
Planting layout and spacing
Space plants 12–18 inches apart at the sunny edge of the bed and pinch the tips often to keep plants bushy and leafy.
Give basil their full spacing of 12–18 inches between plants. Crowded basil 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 basil; scented herbs go closest to the crop, dotted through the row.
Basil are started indoors and transplanted out once the weather warms: sow under cover where needed, expect germination in 5–10 days, and set plants out once the weather is right. Work backwards from your last frost date with the seed-starting calculator. Basil need full sun and soil with a pH of 6.0–7.5. Water needs are moderate, 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 60–70 days from sowing to maturity.
Common problems and fixes
The pests most often reported on basil are aphids, slugs, whiteflies. 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. |
| Slugs | Chewed leaves and silvery trails, worst in damp weather. | Beer traps or copper tape; clear debris. |
| Whiteflies | Tiny white insects that rise in a cloud when disturbed. | Yellow sticky traps; wash leaf undersides. |
Aphids
Wash them off with a strong jet of water and leave ladybirds and lacewings alone to eat them. Check the undersides of young leaves, where colonies start.
Slugs
Slugs feed at night in damp weather. Clear boards, pots and debris where they hide by day, and set beer traps at soil level near the worst-hit plants.
Whiteflies
Put out yellow sticky traps to monitor numbers and wash leaf undersides with water. They breed fastest in warm, still air, so keep airflow good.
Unsure what you are seeing? Try the pest-identifier helper or the plant-disease checker. Remove badly affected leaves and rotate the Lamiaceae family next year.
Frequently asked questions
What is the best companion plant for basil?
The most widely recommended companions are tomatoes. The classic pairing: basil at the feet of tomatoes, where its scent is traditionally said to confuse pests and its flavour is said to improve.
What should not be planted near basil?
Avoid other members of the Lamiaceae family, including Mint, Rosemary, Thyme, Sage. They share the same pests and diseases as basil, so problems move easily between them. Rotate the family to a fresh bed each season.
Can I plant basil with peppers?
Yes. Peppers are on the companion list for basil. Peppers give basil a warm, sheltered spot at their feet, and basil's scent is traditionally said to help confuse pests.
How far apart should basil and their companions be planted?
Space basil plants 12–18 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.