Companion Planting: The Complete Guide + Chart for Every Vegetable

What Is Companion Planting?

Companion planting is the practice of growing different plants near each other to create mutually beneficial relationships. Some plant pairings improve growth and yields, some repel common pests, some attract beneficial insects, and some fix nutrients that neighboring plants need.

It is one of the oldest gardening techniques in the world — practiced by Indigenous farmers long before modern agriculture — and it remains one of the most effective ways to grow more food with fewer inputs.

Why companion planting works:

Pest control without chemicals — aromatic herbs like basil and rosemary confuse or deter pests that hunt by smell
Attract beneficial insects — flowers like marigolds and nasturtiums bring in predatory wasps and hoverflies that eat aphids
Improve soil fertility — legumes (beans, peas, clover) fix atmospheric nitrogen into the soil for neighboring plants
Maximize space — tall plants shade heat-sensitive ground-cover crops; climbing plants use vertical space above sprawling ground crops
Improve pollination — bee-attracting flowers near vegetable crops dramatically increase fruit set on tomatoes, squash, and cucumbers

The Science Behind It

Companion planting effects fall into four categories:

Mechanism	How It Works	Example
Biochemical suppression	Root exudates or volatile compounds deter pests	Marigolds emit thiophenes that repel nematodes
Physical disruption	Dense planting breaks up pest movement paths	Lettuce between brassicas slows cabbage loopers
Habitat provision	Flowers attract beneficial predator insects	Dill and fennel attract parasitic wasps
Nitrogen fixation	Legume root nodules fix N₂ from air	Beans enrich soil for nearby corn and squash

The Complete Companion Planting Chart

Tomatoes

Tomatoes are heavy feeders with many pest pressures. They benefit significantly from companion planting.

Plant	Relationship	Benefit
Basil	✅ Best companion	Repels thrips and aphids; may improve flavor
Marigolds	✅ Excellent	Repel nematodes, whiteflies, aphids
Nasturtiums	✅ Excellent	Trap crop for aphids; attract predator insects
Parsley	✅ Good	Attracts predatory wasps that eat hornworms
Carrots	✅ Good	Loosen soil around tomato roots
Borage	✅ Good	Repels tomato hornworm; attracts bees
Fennel	❌ Avoid	Inhibits tomato growth via allelopathic compounds
Corn	❌ Avoid	Attracts similar pests; competes for resources
Brassicas	❌ Avoid	Heavy feeders that compete for the same nutrients

Peppers

Plant	Relationship	Benefit
Basil	✅ Best companion	Repels aphids and spider mites
Marigolds	✅ Excellent	Repel nematodes and whiteflies
Carrots	✅ Good	Good space use; don't compete heavily
Spinach	✅ Good	Ground cover reduces moisture loss
Fennel	❌ Avoid	Allelopathic — inhibits pepper growth
Beets	❌ Avoid	Compete for the same nutrients

Cucumbers

Plant	Relationship	Benefit
Nasturtiums	✅ Best companion	Trap crop for cucumber beetles and aphids
Dill	✅ Excellent	Attracts beneficial insects; deters aphids
Marigolds	✅ Excellent	Repel cucumber beetles
Beans	✅ Good	Fix nitrogen; cucumbers are heavy feeders
Radishes	✅ Good	Repel cucumber beetles when planted nearby
Sage	❌ Avoid	Inhibits cucumber growth
Potatoes	❌ Avoid	Both attract similar blights and diseases

Beans and Peas (Legumes)

Plant	Relationship	Benefit
Carrots	✅ Excellent	Beans loosen and aerate soil around carrots
Corn	✅ Excellent	Classic Three Sisters pair; corn gives beans a trellis
Squash	✅ Excellent	Third leg of Three Sisters; shade suppresses weeds
Marigolds	✅ Good	Repel Mexican bean beetles
Savory	✅ Good	Repels bean beetles; improves flavor
Fennel	❌ Avoid	Stunts legume growth
Onions	❌ Avoid	Inhibit bean growth via allicin compounds
Garlic	❌ Avoid	Same as onions — allelopathic to beans

Carrots

Plant	Relationship	Benefit
Onions	✅ Best companion	Onion scent deters carrot fly
Leeks	✅ Excellent	Mutual pest deterrence
Rosemary	✅ Excellent	Aromatic foliage repels carrot fly
Sage	✅ Good	Strong scent masks carrot scent
Lettuce	✅ Good	Shallow roots; don't compete
Dill	❌ Avoid	Stunts carrot growth when mature (ok as seedlings)
Beets	❌ Avoid	Both prefer same deep soil; compete

Lettuce and Salad Greens

Plant	Relationship	Benefit
Carrots	✅ Excellent	Different root depths; no competition
Radishes	✅ Excellent	Quick-growing; harvest before lettuce shades them
Chives	✅ Good	Repel aphids; mild pest deterrence
Nasturtiums	✅ Good	Trap crop for aphids away from lettuce
Tall crops	❌ Avoid	Deep shade stunts lettuce; light shade is acceptable

Brassicas (Cabbage, Broccoli, Kale)

Plant	Relationship	Benefit
Dill	✅ Excellent	Attracts parasitic wasps that control caterpillars
Nasturtiums	✅ Excellent	Trap crop for cabbage aphids
Thyme	✅ Good	Deters cabbage worms and whiteflies
Sage	✅ Good	Repels cabbage moths and white butterflies
Marigolds	✅ Good	General pest deterrence
Strawberries	❌ Avoid	Both attract botrytis; inhibit each other
Tomatoes	❌ Avoid	Heavy feeders competing for the same nutrients

Herbs: What to Plant Together

Herb	Good Companions	Avoid
Basil	Tomatoes, peppers, oregano	Sage (inhibits each other)
Rosemary	Carrots, beans, sage, thyme	Mint (invasive; stunts rosemary)
Mint	Brassicas, peas, tomatoes	Everything (keep in containers — invasive)
Dill	Cucumbers, brassicas, lettuce	Carrots (mature dill stunts them), fennel
Chives	Carrots, tomatoes, roses	Beans, peas (onion family inhibits legumes)
Chamomile	Most vegetables	None notable
Lavender	Most vegetables	None notable

The Three Sisters: The Original Companion Planting System

The Three Sisters is the most famous companion planting system in the world, developed by Indigenous peoples of North America centuries ago. It is as effective today as it was then.

The three plants:

Corn — grows tall, provides a living trellis for beans
Beans — climb the corn stalks; fix nitrogen into the soil for corn and squash
Squash — sprawls along the ground; large leaves shade out weeds and retain soil moisture

Why it works so well:

Each plant fills a different ecological niche (vertical layers, soil nitrogen, ground cover)
Beans feed the heavy-feeding corn and squash
Squash suppresses weeds that would otherwise compete
The combination produces a balanced diet: carbohydrates (corn), protein (beans), vitamins (squash)

How to Plant Three Sisters

Step 1: Prepare your bed

Work 3–4 inches of compost into a raised or in-ground bed. Three Sisters needs full sun (minimum 6 hours). A 4×8 foot bed can accommodate one Three Sisters grouping, or plant in the traditional mound style.

Step 2: Plant corn first

Plant corn seeds 1 inch deep, 12–18 inches apart, in blocks of at least 4×4 plants (not rows — corn is wind-pollinated and needs density for good pollination). Wait until soil is reliably above 60°F / 15°C.

Step 3: Add beans 2 weeks later

Once corn is 4–6 inches tall, plant 3–4 pole bean seeds in a circle 6 inches from each corn stalk. Pole beans, not bush beans — they need to climb.

Step 4: Add squash 2 weeks after beans

When beans have germinated, plant squash seeds or transplants 18–24 inches from the base of the corn mounds. One squash plant covers 4–6 square feet — give it room.

Step 5: Maintain and harvest in sequence

Corn tassels and silks first → beans follow → squash continues producing until frost. Harvest each as it ripens. At season end, the bean roots leave nitrogen-enriched soil for next year's plantings.

Companion Planting for Pest Control

The Trap Crop Strategy

A trap crop is a sacrificial plant that pests prefer over your main crop. Plant it nearby to lure pests away.

Pest	Trap Crop	Main Crops Protected
Aphids	Nasturtiums	Tomatoes, cucumbers, beans
Cabbage aphids	Nasturtiums	Kale, cabbage, broccoli
Cucumber beetles	Blue Hubbard squash	Cucumbers, melons
Flea beetles	Arugula	Eggplant, peppers
Thrips	Basil	Tomatoes, peppers

The Repellent Strategy

Aromatic herbs and flowers planted as a border or interplanted confuse pest insects that navigate by smell.

Repellent Plant	Pests Deterred	How to Use
Marigolds	Nematodes, whiteflies, aphids	Border + interplanted throughout
Basil	Thrips, aphids, spider mites	Every 3–4 tomato/pepper plants
Rosemary	Carrot fly, bean beetles	Near carrot rows
Mint	Aphids, flea beetles, ants	Contained pots placed nearby
Lavender	Moths, fleas, whiteflies	Garden border
Chives	Aphids, Japanese beetles	Interplanted throughout

The Beneficial Insect Strategy

Predatory insects — ladybugs, lacewings, parasitic wasps, hoverflies — eat the pests that damage your vegetables. Flowering plants attract and feed these beneficial insects.

Best plants for beneficial insects:

Dill and fennel — attract parasitic wasps that parasitize caterpillars and aphids
Chamomile — attracts hoverflies and parasitic wasps
Marigolds — attract hoverflies whose larvae eat aphids
Nasturtiums — attract hoverflies and beneficial predatory insects
Lavender — attracts bees and many generalist predators
Zinnia — excellent for butterflies and beneficial wasps

Companion Planting for Better Yields

Some plant combinations appear to improve growth and flavor through biochemical mechanisms that are still being studied.

Combination	Reported Effect
Basil + tomatoes	Improved flavor; some studies show increased essential oil production in both
Chamomile + most vegetables	Thought to stimulate growth via apigenin root exudates
Borage + strawberries	Boron from borage leaves said to improve fruiting
Dill + cabbage	Improved head development reported by many growers
Comfrey as mulch	Potassium-rich leaves improve fruiting crops when used as mulch

Note: Many of these effects are based on long-term grower observation rather than controlled trials. The soil health and pest control benefits of companion planting are much more rigorously documented than flavor or yield effects.

Flowers as Companion Plants

Flowers are not optional in a vegetable garden — they are functional tools.

The best companion flowers:

Marigolds

The most useful companion plant in any vegetable garden. French marigolds (Tagetes patula) produce thiophene compounds from their roots that repel and kill root-knot nematodes. All marigolds repel whiteflies, aphids, and many beetles with their scent. Plant throughout the garden, not just as a border.

Nasturtiums

A dual-purpose companion: they attract aphids and cucumber beetles as a trap crop AND attract the hoverflies that eat aphids. Their edible flowers and leaves are a bonus harvest. Plant freely throughout the vegetable garden.

Borage

Attracts bees and other pollinators; repels tomato hornworm; its starflower is edible. Borage self-seeds prolifically — plant once and it will reappear every year.

Zinnias

Powerhouse pollinator plants that attract butterflies, bees, and beneficial wasps. Easy to grow from seed directly sown; bloom all summer with deadheading.

Calendula

Attracts beneficial insects; repels aphids and whiteflies; edible flowers. Self-seeds each year. Excellent border plant.

How to Implement Companion Planting in Your Garden

Step 1: Audit your garden layout

Map your growing space. Identify your main crops (tomatoes, cucumbers, beans, brassicas, etc.) and note how much space each has. Companion planting works best when you plan it into your layout before planting, not as an afterthought.

Step 2: Choose your primary companion strategy

Decide whether you are primarily addressing: pest control, pollination, nitrogen fixing, or space efficiency. Different strategies require different companion choices.

Step 3: Select 3–5 companion plants

Do not try to implement every companion planting combination at once. Choose 3–5 companion plants that address your specific challenges. Marigolds, basil, and nasturtiums solve 80% of companion planting needs for a typical vegetable garden.

Step 4: Plant companions before or with main crops

Companions need to establish before your main crops are threatened by pests. Plant marigolds and other companions at the same time as — or 2 weeks before — your main crop transplants.

Step 5: Use companion plants as borders and interplanting

Plant a perimeter border of pest-deterrent plants AND interplant companions between your main crops. A border stops pests from entering; interplanting disrupts their movement within the garden.

Step 6: Rotate companions with your crops

Companion planting works best as part of a crop rotation plan. Rotate companions along with their partner plants to prevent soil-borne disease buildup and maintain soil health across the whole garden.

Common Companion Planting Mistakes

Planting mint in the ground — Mint will take over the entire garden within one season. Always grow mint in containers and place them near target crops.
Planting fennel with anything — Fennel is allelopathic: it exudes compounds that inhibit the growth of most vegetable crops. Grow fennel in its own isolated bed or pot.
Relying on companion planting alone for pest control — Companion planting significantly reduces pest pressure but rarely eliminates it. It works best as one layer of an integrated pest management approach.
Skipping the flowers — Many gardeners implement companion planting with only herbs and miss the powerful pest control and pollination benefits of flowering companions.
Planting in a single row instead of blocks — Companion planting effects are diluted in a single-row intercrop. Plant companions in masses and blocks for meaningful impact.
Not giving companions enough space — Cramped companions compete with the very crops they are meant to help. Follow standard spacing for every plant, companion or main crop.

FAQ

What is the best companion plant for tomatoes?

Basil is widely considered the best companion plant for tomatoes. It repels thrips and aphids, and many growers report improved tomato flavor when basil is grown nearby. Marigolds are a close second — they repel nematodes, whiteflies, and aphids, and are especially effective when interplanted throughout the tomato bed rather than just as a border. Plant one basil plant for every two to three tomato plants and marigolds every 12–18 inches throughout the bed.

What should you not plant together?

The most important combinations to avoid are: fennel near almost anything (it inhibits growth of most vegetables), onions and beans/peas (allium compounds inhibit legume nitrogen fixation), tomatoes near corn (they attract similar pests and compete heavily), and potatoes near cucumbers (both are susceptible to similar blights). Mint near any other herb in the ground is also problematic — its invasive root system will crowd out neighbors. Grow mint in a container.

Does companion planting actually work?

Yes, for pest control and pollination improvement, the evidence is strong. The nematode-repelling effect of marigolds is well-documented in peer-reviewed research. The role of flowering companion plants in attracting predatory insects is similarly well-supported. Nitrogen fixation by legumes is firmly established science. The yield and flavor improvement claims (basil improving tomato flavor, chamomile stimulating growth) are based more on grower observation than controlled research, but the overall effect of a well-planned companion planting system on pest pressure and biodiversity is measurably positive.

What is the Three Sisters planting method?

The Three Sisters is a companion planting system developed by Indigenous peoples of North America that grows corn, beans, and squash together. Corn provides a living trellis for beans to climb. Beans fix nitrogen from the air into the soil, feeding the heavy-feeding corn and squash. Squash sprawls across the ground, shading out weeds and retaining soil moisture with its large leaves. Each plant fills a different niche, and together they produce more food per square foot than any of the three grown separately, while also building soil fertility.

How close should companion plants be planted?

For scent-based deterrence (like basil near tomatoes), plant companions 12–18 inches away — close enough for the aromatic compounds to be effective, but not so close they compete for the same root space. For trap crops (like nasturtiums for aphids), plant them 12–24 inches from the target crop so pests are diverted before reaching the main plants. For beneficial insect habitat (flowering companions), clusters of 5–10 plants are more effective than single plants spread throughout the garden.

Can I practice companion planting in containers?

Yes, container companion planting works well. Plant one basil plant in the same pot as a tomato or pepper, or place a pot of mint or chives nearby. Marigolds in a separate container positioned near tomatoes provide pest deterrence. The main limitation is root space — avoid combining plants with similar large root systems in the same container. Herbs (basil, parsley, chives) pair well with almost any vegetable in a shared large container (minimum 12–15 inches deep).

What companion plants fix nitrogen in the soil?

All legumes fix nitrogen: beans, peas, clover, vetch, and lupins all have root nodules containing Rhizobium bacteria that convert atmospheric nitrogen into plant-available ammonia. After the season, leave legume roots in the soil to decompose and release their nitrogen. Green manure legumes (clover, vetch, field peas) are sometimes grown specifically to be tilled in as a soil amendment. For companion planting, pole beans and bush beans are the most practical nitrogen-fixing companions for a vegetable garden.