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Companion Planting Guide

Select a crop to instantly see which plants grow best alongside it — and which to keep well apart — with the science behind each pairing.

Select a Crop

Select a crop above to see its companion planting guide.

What Is Companion Planting?

Companion planting is the practice of growing different plants close together for mutual benefit. The right pairings can deter pests, attract beneficial insects, improve soil fertility, and boost yields — all without chemical intervention.

The mechanisms work in several ways. Some plants release compounds through their roots (allelopathy) that suppress weeds or inhibit nearby plants — fennel is the classic example, inhibiting almost everything around it. Others release volatile chemicals through their leaves that confuse or repel pest insects: basil near tomatoes masks the scent that attracts whitefly and aphids.

Nitrogen-fixing legumes (peas, beans) convert atmospheric nitrogen into a form other plants can use — growing them near heavy feeders like corn or squash is essentially free fertilizer. Tall plants like sunflowers provide natural trellises and shade for more delicate crops below.

The evidence for companion planting ranges from well-supported science (French marigold root secretions killing nematodes is thoroughly documented) to traditional wisdom that has worked reliably for thousands of years. Use it as one layer of your growing strategy alongside crop rotation and good soil care.

Quick Companion Reference

The most useful companion pairings at a glance. Select any crop above for the full details.

Crop Best Companions Keep Away From
🍅 Tomato Basil, Marigold, Carrot, Chives Fennel, Potato, Brassicas
🌶️ Pepper Basil, Carrot, Marigold, Onion Fennel, Brassicas
🥒 Cucumber Beans, Dill, Peas, Radish, Marigold Potato, Sage, Melon
🥬 Zucchini Beans, Corn, Marigold, Nasturtium Potato, Fennel, Pumpkin
🥕 Carrot Onion, Leek, Rosemary, Tomato Dill, Parsley, Beets
🥗 Lettuce Carrot, Radish, Chives, Onion Celery, Parsley, Fennel
🫛 Green Beans Carrot, Cucumber, Corn, Radish Garlic, Onion, Fennel
🫛 Peas Carrot, Mint, Radish, Spinach, Corn Garlic, Onion, Leek
🧅 Onion Carrot, Beets, Tomato, Lettuce Beans, Peas, Asparagus
🧄 Garlic Tomato, Rose, Carrot, Beets Beans, Peas, Asparagus
🌿 Basil Tomato, Pepper, Asparagus Sage, Fennel
🌼 Marigold Tomato, Cucumber, Beans, Potato Fennel
🥔 Potato Beans, Marigold, Basil Tomato, Cucumber, Sunflower

Why Companion Planting Works

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Pest Deterrence

Some plants release volatile compounds that mask the scent of neighbouring crops from pest insects, or simply smell so unpleasant that insects avoid the area. Basil near tomatoes is a well-known example.

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Attracting Beneficials

Flowers like marigolds, dill and fennel attract predatory wasps, hoverflies and ladybugs that feed on aphids, caterpillars and other soft-bodied pests — turning your garden into a self-policing ecosystem.

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Nitrogen Fixation

Legumes (peas, beans, clover) host bacteria in their roots that convert atmospheric nitrogen into ammonia — a plant-available nutrient. Planting them near heavy feeders like corn, squash and brassicas is essentially organic fertilization.

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Allelopathy

Some plants actively inhibit their neighbours by releasing chemicals through their roots or leaves. Fennel is the most notorious — it inhibits almost everything. Black walnut is another. Knowing what to keep apart is as important as knowing what to plant together.

☀️

Physical Structure

Tall crops like sunflowers, corn and Jerusalem artichoke provide natural shade and wind protection for delicate plants below. Sprawling squash and pumpkin suppress weeds as living mulch.

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Trap Cropping

Sacrificial plants attract pests away from your main crop. Nasturtiums draw aphids away from vegetables; mustard attracts flea beetles; Blue Hubbard squash lures squash vine borers away from zucchini.

Frequently Asked Questions

Does companion planting actually work?

Yes — for many pairings, the evidence is strong. French marigold root secretions have been shown in multiple studies to significantly reduce nematode populations. Basil near tomatoes demonstrably reduces whitefly. Legume nitrogen fixation is well-established science. Other benefits, like "improving flavour," have less rigorous evidence and are based on gardening tradition. Use well-documented pairings (pest deterrence, nitrogen fixation, trap cropping) as your foundation, and treat flavour benefits as a bonus.

How close do companion plants need to be?

For volatile-compound-based deterrence (basil, marigolds, chives), plant within 12–24 inches of the crop you want to protect. For root-based effects (nematode suppression, nitrogen fixation), the plants need to share soil — within the same bed. For physical effects (shade, structure), simply ensure one plant is on the windward or sun side of the other.

Why is fennel kept away from everything?

Fennel is strongly allelopathic — it releases chemicals from its roots and foliage that inhibit germination and root growth in most other plants. Tomatoes, peppers, beans, and even basil all grow poorly near fennel. Grow fennel in its own isolated container or in a far corner of the garden where it cannot affect other crops.

What is the Three Sisters planting method?

The Three Sisters is a Native American intercropping system using corn, beans, and squash together. Corn provides a vertical pole for beans to climb. Beans fix nitrogen that feeds the heavy-feeding corn and squash. Squash spreads along the ground, shading out weeds and retaining soil moisture with its large leaves. The three crops support each other's needs completely, and together they produce far more food per square foot than any of them grown alone.

Can companion planting replace pest control?

Companion planting significantly reduces pest pressure but should be part of a broader integrated pest management strategy — not your only line of defence. Combine it with regular monitoring, crop rotation, physical barriers (row covers, copper tape), and good garden hygiene (removing diseased leaves promptly). The goal is to create a balanced ecosystem where pest populations are naturally suppressed, not to eliminate all pests entirely.

More Free Gardening Tools

Plan your garden from seed to harvest.

EdenVatika App

Know your companions.
Now plan your whole garden around them.

EdenVatika checks companion compatibility for every crop in your beds automatically — and flags any antagonistic pairings before you plant, saving you from a season of reduced yields.

  • 🌱

    Smart bed planner

    Drag and drop crops into beds and get instant compatibility feedback

  • ⚠️

    Conflict warnings

    Flags antagonistic pairs in your layout before you plant (Pro)

  • 🔁

    Crop rotation tracking

    Knows what you grew last year to suggest this year's rotation

  • 📋

    Planting reminders

    Get alerts when it's time to sow, transplant or harvest (Pro)

  • 🤖

    AI companion suggestions

    Tell the AI what you want to grow and it builds a companion-optimized layout (Pro)

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