Companion Planting Guide: Which Vegetables Grow Well Together

Companion planting — the idea that some plants thrive next to each other and others should be kept apart — is one of those gardening topics where the internet’s advice ranges from genuinely useful to total folklore. This guide cuts through the noise, focuses on the pairings backed by either solid research or repeated home-garden experience, and is honest about which “rules” you can ignore.

What companion planting actually does (when it does anything)

Real companion-planting effects fall into a few categories:

• Pest deterrence. Aromatic herbs and flowers (basil, marigolds, nasturtiums) release scents that confuse or repel some pest insects. Effect is real but moderate — won’t replace pest scouting.
• Pollinator attraction. Flowers planted near fruiting crops bring more bees, increasing fruit set on tomatoes, squash, cucumbers.
• Nitrogen fixation. Legumes (beans, peas) host bacteria that fix atmospheric nitrogen into soil-usable form. Real benefit, especially for next-season crops in the same bed.
• Physical structure. Tall plants shade short plants; dense plants suppress weeds for sparser plants. Three Sisters (corn-beans-squash) is the textbook example.
• Root exudates. Some plants release chemicals through their roots that affect neighbors. Only a few well-documented pairings here (e.g., black walnut suppresses tomatoes).

What companion planting does NOT do reliably:

• “Boost flavor” of nearby crops (no real evidence)
• Significantly increase yields beyond what good spacing already does
• Replace integrated pest management when pest pressure is high

So treat companion planting as a layer of small advantages that add up — not magic.

The reliable companions

These pairings are well-supported and worth following:

Tomato + basil

The textbook companion. Basil’s strong scent confuses tomato-hornworm moths (the pest that lays eggs producing leaf-stripping caterpillars). Both crops want similar conditions: full sun, regular water, warm soil. Plant basil 12–18” from each tomato base.

Tomato + marigold

Marigolds (especially French marigolds) release thiopene compounds from roots that suppress nematodes — microscopic root pests that damage tomato roots. Effect is most useful if you have nematode pressure (warm climates, sandy soils). Plant marigolds at the corners of the tomato bed.

Carrot + onion / scallion

Onions deter the carrot rust fly via scent; carrots deter the onion fly. Mutual pest deterrence. Plant in alternating rows or interplanted within the same row.

Cucumber + dill

Dill flowers attract beneficial wasps that prey on cucumber-beetle larvae. Plant dill at the bed edge so the cucumbers get sun and the dill flowers attract pollinators.

Beans + corn + squash (Three Sisters)

The classic Indigenous American polyculture. Corn provides vertical support for the bean vines. Beans fix nitrogen for the corn (heavy nitrogen feeder). Squash spreads at ground level, shading out weeds and shielding soil moisture. All three crops benefit. Requires a larger bed (8×8 minimum), so it’s not ideal for a small raised bed.

Lettuce + tall sun-lovers (tomato, pepper)

Lettuce wants partial shade and bolts (goes to seed) in summer heat. Plant lettuce in the shadow of taller plants — to the east of tall plants if possible — to extend the lettuce season into early summer.

Brassicas (cabbage, broccoli, kale) + thyme / sage / rosemary

Aromatic herbs deter cabbage moths (the pest behind the green caterpillars that destroy brassicas). Plant herbs along the bed perimeter.

The ones to keep apart

These pairings actively harm each other or compete heavily:

Tomato + brassicas (cabbage, broccoli, kale, brussels sprouts)

Brassicas are heavy feeders that strip the soil of nutrients tomatoes need. They also harbor cabbage moths that, while not direct tomato pests, can damage other plants nearby. Plant in separate beds.

Onion / garlic + beans / peas

Alliums (onion family) release compounds that suppress nitrogen-fixing bacteria on legume roots. The legumes underperform. Keep them in different sections.

Fennel + most things

Fennel is famously antisocial. Its root exudates suppress germination of many vegetables, especially beans, tomatoes, and cucumbers. Plant fennel in its own corner — or skip it for an in-bed planting.

Potato + tomato

Both are nightshades and share diseases (especially early blight and late blight). Plant in separate beds and rotate yearly to break disease cycles.

Cucurbits (cucumber, squash, melon) + potato

Potatoes harbor blight that can spread to cucurbits. Same reason as the tomato/potato rule — separate them.

The “rules” that are mostly myth

The internet repeats these but evidence is weak:

• “Plant garlic near roses to deter aphids.” Some pest deterrence at very close spacing, but garlic doesn’t broadcast its effect — you’d need garlic packed tightly around each rose.
• “Plant chamomile to improve cucumber flavor.” No evidence. Chamomile is a fine pollinator attractor; that’s the only verifiable benefit.
• “Mint repels everything.” Mint repels almost no garden pests reliably; what it does do is spread aggressively and choke out other plants. Always grow mint in a container, not in a shared bed.
• “Plant sunflowers next to corn to attract pollinators.” Corn is wind-pollinated, not insect-pollinated. The sunflowers don’t help; if anything, they shade the corn.

Save your bed space and your effort for pairings with real evidence.

A practical companion-planting layout

For a 4×8 raised bed using companion-planting principles:

North side (back, full sun)
[Tomato] [Tomato] [Pepper] [Pepper]
   |        |       |        |
   basil   basil    -        -
[Carrots interplanted with onions]   [Bush beans]
[Lettuce] [Lettuce]  [Marigold]      [Lettuce]
South side (front)

This layout uses: - Tomato + basil pairing (pest deterrence) - Tomato + marigold (nematode suppression) - Carrot + onion (mutual pest deterrence) - Lettuce in afternoon shade of tomatoes (extends harvest season) - Beans on one end (nitrogen for next year’s heavy feeders)

Using companion planting in small spaces

In a 4×4 raised bed, you can’t separate every conflicting crop into different beds. The honest answer: don’t grow crops with strong incompatibilities together at all. Pick one of:

• Tomato-centered bed (tomatoes + peppers + basil + lettuce + carrots — all compatible)
• Brassica-centered bed (cabbage + broccoli + kale + thyme + lettuce — all compatible)
• Bean-centered bed (bush beans + cucumbers + dill + marigolds — all compatible)

Just don’t try to grow tomatoes AND brassicas in 16 sq ft. Pick a theme.

Companion planting and pest control aren’t the same thing

Even with perfect companion planting, you’ll still get pests. Companion plants reduce pest pressure but don’t eliminate it. You still need to:

• Inspect plants weekly for eggs and larvae on leaf undersides
• Remove pest-damaged leaves quickly (don’t let damage cascade)
• Use row cover for high-pressure pests (cabbage moths, squash vine borer)
• Encourage beneficials by leaving some dill, parsley, or yarrow flowering at all times

The companion-planting effect is best thought of as a 10–20% reduction in pest pressure, not a substitute for hands-on pest scouting.

Plan companions when you plan the rest

Companion planting works best when you bake it into your overall garden plan rather than retrofitting it. The Planter App lets you pick crops and shows you what fits in your space; the suggested pairings here can guide which crops to combine in the same plan.

Plan a companion-friendly garden →

Related guides

• What to plant in a 4×4 raised bed — concrete layouts that respect companion principles
• When to plant tomatoes by zone — timing for the most popular companion-planting anchor
• 8 vegetables that almost always succeed for beginners