Companion Planting Guide

Vegetables and flowers growing together in a companion-planted garden bed

What to plant with tomatoes, carrots, beans and more, with an honest look at what works

Companion planting is the practice of growing certain plants near each other so they help one another, and keeping apart the ones that do not get along. Done well, it draws in helpful insects, confuses pests, makes better use of space, and can lift the health of a whole bed. Done as blind superstition, it does very little. This guide gives you a practical, accurate picker for 30 common crops, a quick chart, the classic combinations explained, and a clear-eyed note on what the evidence actually supports.

What companion planting really does

There are a handful of real mechanisms behind companion planting. Some are well supported by research, others are traditional wisdom that has worked for generations without being formally proven. The honest position is that companion planting stacks small advantages. Here are the levers that matter:

Attracting beneficial insects. Flowering plants like marigold, nasturtium, alyssum and let-them-bolt herbs such as coriander and dill draw in hoverflies, lacewings, predatory wasps and bees. These hunt aphids and caterpillars and pollinate your crops. This is the best-evidenced benefit of all.
Pest confusion and masking. Strong-smelling herbs and a mix of plant shapes can make it harder for a pest to find its host crop than a clean monoculture row. The effect is real but modest, and works best as part of a diverse planting rather than one herb dotted about.
Nitrogen fixing. Peas, beans and other legumes partner with soil bacteria to pull nitrogen from the air into the soil. Following a legume with a hungry leafy crop is a genuine, measurable benefit.
Shade, shelter and structure. Tall plants shelter tender ones, and a sprawling crop can act as living mulch. The Three Sisters, where corn supports beans and squash shades the soil, is the classic example.
Trap cropping. A sacrificial plant draws pests away from your main crop. Nasturtium pulling aphids off beans is a familiar example.

An honest note on evidence. Some pairings are well researched, such as French marigolds suppressing root-knot nematodes and legumes fixing nitrogen. Others, like the idea that a single basil plant transforms the flavour of a tomato, are traditional and not strongly proven. Treat companion planting as a helpful guide, not a hard rule, and you will get the best of it.

What pairs with...

Pick a crop below to see its best companions, the ones to keep apart, and the reason for each. Every pairing here is a widely accepted one, and where a benefit is traditional rather than proven we have kept the claim modest.

Choose a crop

Quick-reference companion chart

A short version for the most popular crops. The picker above has the full detail and the reason behind each pairing.

Crop	Good with	Keep apart from
Tomato	Basil, marigold, parsley, chives, carrot, lettuce, nasturtium	Brassicas, fennel, potato, corn
Capsicum & chilli	Basil, carrot, onion, marigold, nasturtium	Fennel, brassicas
Cucumber	Beans, peas, corn, nasturtium, dill, radish	Potato, strong aromatic herbs like sage
Zucchini & pumpkin	Corn, beans, nasturtium, marigold	Potato
Bean	Corn, squash, carrot, cucumber, lettuce	Onion, garlic, fennel
Pea	Carrot, cucumber, beans, lettuce, radish	Onion, garlic
Corn	Beans, squash, cucumber, lettuce	Tomato
Carrot	Onion, leek, lettuce, peas, rosemary	Dill, fennel
Onion & garlic	Carrot, beetroot, lettuce, brassicas, strawberry	Beans, peas
Lettuce	Carrot, radish, beetroot, onion, tall crops for shade	None of note
Brassicas (cabbage, broccoli)	Aromatic herbs, onion, beetroot, nasturtium, dill	Tomato, strawberry, beans
Beetroot	Onion, lettuce, brassicas, bush beans	Climbing beans
Potato	Beans, corn, marigold, horseradish	Tomato, cucumber, pumpkin
Strawberry	Lettuce, spinach, onion, borage, thyme	Brassicas
Basil	Tomato, capsicum, chilli, oregano	None of note

Classic combinations explained

The Three Sisters: corn, beans and squash

The most famous companion system of all, developed by Indigenous farmers across the Americas. The corn grows tall and gives the climbing beans a living pole. The beans fix nitrogen in the soil, feeding the heavy-feeding corn. The squash sprawls across the ground, its big leaves shading out weeds and keeping the soil cool and moist. Three crops sharing one patch, each doing a job for the others. It is reliable because every part of it rests on a real mechanism.

Tomato, basil and marigold

A kitchen-garden classic. Basil grows happily alongside tomatoes and the pair ends up on the same plate, so it is convenient as well as traditional. Both basil flowers and marigold draw in pollinators and predatory insects, and French marigolds grown as a block can reduce root-knot nematodes in the soil. The flavour-boosting claim is folklore, but the insect and soil benefits are real enough to make this a worthwhile trio.

Carrots and onions

An old pairing built on pest confusion. The smell of onions is thought to mask carrots from the carrot fly, and the smell of carrots to muddle the onion fly. The evidence is mixed, but the two interleave neatly, use the bed efficiently, and do each other no harm, so it remains a sensible combination.

Lettuce under taller crops

Pure use of space and light. Lettuce and other leafy greens bolt and turn bitter in fierce summer sun. Tucked into the shade of staked tomatoes, climbing beans or sweet corn, they stay tender and cropping for longer while making use of ground that would otherwise sit bare. This one is simple, practical and works every time.

What companion planting will not do

Companion planting is a helper, not a cure. It will not rescue a garden built on poor foundations. Keep your expectations honest:

It is not a substitute for healthy soil. No pairing beats compost, mulch and good drainage. Feed the soil first and companions are the finishing touch.
It does not replace crop rotation. Moving families of crops around the garden each season is what breaks pest and disease cycles. Companion planting works alongside rotation, not instead of it. See the idea in our Connections story for how a bed's history shapes what to plant next.
It is not pest control on its own. You still need to watch your plants. Attracting predators helps, but a bad aphid or caterpillar run needs you to notice and act. Pair this with a pest-watch routine and our Pest & Disease Guide.
It will not fix the wrong plant in the wrong spot. A sun-lover in shade, or a tender crop planted out into frost, will struggle no matter what grows beside it.

Plan companions alongside your beds

Add your crops to your garden in the Planting Season app and plan companions bed by bed, with the right plants grouped together and the clashes flagged before you sow.

Open the App →

Frequently Asked Questions

What are the best companion plants for tomatoes?

Basil, marigold, parsley, chives, carrots, lettuce and nasturtium all make good tomato companions. Basil and marigold are the classic pairing, planted to help draw in helpful insects and make use of the space. Avoid planting tomatoes near brassicas like cabbage and broccoli, near fennel, and near potatoes, which share pests and diseases.

What should I not plant near tomatoes?

Keep tomatoes away from brassicas such as cabbage, broccoli and cauliflower, which compete heavily and host overlapping pests. Avoid fennel, which inhibits many vegetables, and avoid potatoes, since both are in the same family and share blight and pests. Corn is also best kept apart as it shares the tomato fruitworm, also known as the corn earworm.

Do marigolds really work as companion plants?

Some of it is well evidenced and some is tradition. French marigolds are shown to suppress certain root-knot nematodes in the soil, which is a real, researched effect, though it works best when grown as a dense block and dug in rather than dotted around. The idea that marigolds repel all pests above ground is more folklore. They do attract hoverflies and other beneficial insects, so they earn their place either way.

What are good companion plants for a small bed?

In a small bed, lean on plants that share space well rather than compete. Lettuce and other leafy greens grow happily in the shade of taller tomatoes or beans. Carrots and onions interleave neatly. A few herbs like basil, parsley and chives, plus a border of marigold or nasturtium to pull in beneficial insects, give you a productive, balanced bed without crowding.

Does companion planting actually work?

Parts of it do. The strongest, best-evidenced mechanisms are attracting beneficial insects with flowering plants, nitrogen fixing by legumes, physical structure and shade like the Three Sisters, and trap cropping. Some traditional pairings have little hard evidence behind them. Treat companion planting as a helpful guide that stacks small advantages, not a magic rule, and pair it with healthy soil, crop rotation and pest monitoring.

What can I plant with capsicum and chillies?

Capsicum and chillies do well with basil, carrots, onions, marigold and nasturtium, much like their relative the tomato. Keep them away from fennel and from brassicas, which compete and host overlapping pests. Basil planted nearby is a popular pairing and the flowers help draw in pollinators and predatory insects.

What is the Three Sisters planting?

The Three Sisters is the classic combination of corn, climbing beans and squash grown together. The corn gives the beans a pole to climb, the beans fix nitrogen that feeds the heavy-feeding corn, and the squash sprawls across the ground as a living mulch that shades out weeds and keeps the soil cool. It is one of the most reliable and best-known companion systems.