Companion planting is the practice of growing certain plants near each other for mutual benefit — improved growth, natural pest control, better pollination, and more efficient use of garden space. It is one of the oldest agricultural techniques in the world, practiced for centuries by indigenous peoples and traditional farmers long before modern science began explaining why certain combinations work.
The Three Sisters planting (corn, beans, and squash grown together) practiced by Native American peoples is perhaps the most famous companion planting system. Corn provides a climbing structure for beans, beans fix nitrogen in the soil that feeds the corn and squash, and squash shades the ground with broad leaves that suppress weeds and retain moisture. Each plant solves a problem for the others — a beautiful example of ecological synergy that modern companion planting builds upon.
This guide provides a comprehensive companion planting chart covering the most popular garden vegetables, herbs, and flowers, explains the science behind why certain combinations work, and identifies the partnerships to avoid that can actually reduce your garden productivity.
Key Takeaways
- Companion planting works through four main mechanisms: pest deterrence, pollinator attraction, nutrient sharing, and physical complementarity (shade, support, ground cover)
- Aromatic herbs are the most powerful companion plants — basil, dill, cilantro, and mint repel specific pests while attracting beneficial insects
- Marigolds are the single most useful companion flower, repelling nematodes, aphids, and whiteflies while attracting pollinators
- Some plant combinations are genuinely harmful — fennel inhibits most nearby plants, and onions stunt bean growth through chemical allelopathy
- Companion planting supplements but does not replace good gardening practices like crop rotation, soil health, and proper spacing
How Companion Planting Works: The Science
Pest Deterrence Through Scent Confusion
Many garden pests locate their target plants by scent. A cabbage moth homes in on the sulfurous compounds released by brassica leaves. When you interplant strong-smelling herbs like thyme, sage, or rosemary among your cabbages, their aromatic oils mask the brassica scent, making it harder for pests to find their target. This principle — called olfactory masking or scent confusion — is one of the most well-documented companion planting mechanisms.
Similarly, basil planted near tomatoes confuses the tomato hornworm moth, which relies on tomato plant volatiles to locate egg-laying sites. Studies have shown 30 to 50 percent reductions in certain pest populations through strategic interplanting.
Attracting Beneficial Insects
Companion planting is not just about repelling pests — it is equally about attracting their natural predators. Ladybugs, lacewings, hoverflies, parasitic wasps, and ground beetles are voracious consumers of garden pests, and they can be attracted to your garden by planting specific flowers and herbs. Our beneficial insects guide covers this in depth.
Dill, fennel (planted away from other vegetables), yarrow, sweet alyssum, and members of the carrot family produce the small, accessible flowers that parasitic wasps and hoverflies need for nectar.
Nitrogen Fixation
Legumes (beans, peas, clover) form symbiotic relationships with soil bacteria that convert atmospheric nitrogen into plant-available forms. This nitrogen benefits neighboring plants both during the growing season and after the legume is turned under. Planting beans near nitrogen-hungry crops like corn, squash, and leafy greens provides a natural fertility boost.
Physical Complementarity
Some companion planting benefits are purely physical. Tall crops like corn and sunflowers provide shade for heat-sensitive plants like lettuce and spinach. Sprawling crops like squash shade the ground, suppressing weeds and retaining moisture. Climbing crops like beans use sturdy companions as living trellises.
Complete Companion Planting Chart
Tomatoes
Best companions: Basil (repels hornworms and aphids, may improve flavor), carrots (loosen soil around tomato roots), marigolds (repel whiteflies and nematodes), nasturtiums (trap crop for aphids), parsley (attracts beneficial insects), borage (attracts pollinators, repels hornworms). Avoid: Fennel (inhibits tomato growth), brassicas (heavy feeders competing for nutrients), corn (attracts tomato fruitworm), mature dill (inhibits tomato growth). Learn more in our tomato growing guide.
Peppers
Best companions: Basil (repels aphids and spider mites), carrots, onions (deter many pests), spinach (ground cover in spring), marigolds, petunias (trap crop for aphids). Avoid: Fennel, kohlrabi (stunts pepper growth), beans near hot peppers. See our pepper growing guide.
Beans (Bush and Pole)
Best companions: Corn (classic Three Sisters — beans climb corn, fix nitrogen), squash (shades ground), carrots, cucumbers, eggplant, peas, radishes, strawberries. Avoid: Alliums (onions, garlic — they release compounds that inhibit bean growth), fennel, peppers (especially hot varieties).
Cucumbers
Best companions: Beans (fix nitrogen cucumbers need), corn (provides shade), dill (attracts beneficial insects that prey on cucumber beetles), marigolds, nasturtiums, radishes, sunflowers. Avoid: Potatoes (compete for nutrients and share diseases), aromatic herbs like sage, melons (too much competition).
Squash and Zucchini
Best companions: Corn and beans (Three Sisters), nasturtiums (repel squash bugs and attract pollinators), marigolds, borage (attracts bees essential for squash pollination), radishes, dill. Avoid: Potatoes (shared pest vulnerabilities). Our zucchini guide covers squash cultivation in detail.
Lettuce and Salad Greens
Best companions: Carrots (lettuce shades carrot roots while carrots loosen soil), chives and garlic (repel aphids), radishes, strawberries, tall crops that provide afternoon shade in summer. Avoid: No major antagonistic relationships — lettuce is one of the most companion-friendly vegetables.
Carrots
Best companions: Onions and leeks (their strong scent masks carrot scent from carrot rust fly — one of the most well-documented relationships), tomatoes, lettuce, rosemary, sage, chives. Avoid: Dill (closely related, can cross-pollinate and attract shared pests), celery (competes for nutrients). Our carrot growing guide provides complete cultivation instructions.
Brassicas (Broccoli, Cabbage, Cauliflower, Kale)
Best companions: Dill (attracts parasitic wasps that control cabbage worms), chamomile, onions and garlic (deter cabbage moths), nasturtiums (trap crop for aphids), thyme, sage, rosemary. Avoid: Strawberries, tomatoes and peppers (heavy feeders competing for same nutrients).
Alliums (Onions, Garlic, Leeks, Shallots)
Best companions: Carrots (classic partnership — each repels the other’s primary pest), beets, lettuce, strawberries, tomatoes, peppers, brassicas, chamomile. Garlic deters aphids, spider mites, and Japanese beetles. Our garlic growing guide covers details. Avoid: Beans and peas (alliums inhibit legume growth).
The Power Players: Best Companion Herbs and Flowers
Basil
The king of companion herbs. Basil repels aphids, mosquitoes, tomato hornworms, and whiteflies. It attracts pollinators when allowed to flower. Interplant with tomatoes, peppers, and any crop troubled by aphids.
Marigolds
French marigolds (Tagetes patula) are the single most useful companion flower. Their roots release alpha-terthienyl, a compound that kills root-knot nematodes — this effect is so well-documented that agricultural researchers recommend marigold cover crops in nematode-infested fields. Above ground, their strong scent repels whiteflies, aphids, and cabbage moths. Plant marigolds throughout the vegetable garden.
Nasturtiums
Nasturtiums serve as trap crops — aphids, whiteflies, and cabbage butterflies strongly prefer nasturtiums over vegetables. Planting them around the perimeter of vegetable beds draws pests away from your food crops. Both flowers and leaves are edible with a peppery flavor.
Dill
Dill attracts parasitic wasps, hoverflies, and ladybugs with its umbel-shaped flowers. It is particularly effective near brassicas. Important note: mature dill may inhibit tomato growth, so keep dill at a distance from tomato plants.
Borage
Borage is a phenomenal pollinator attractor — bees are irresistibly drawn to its blue star-shaped flowers. Plant near any crop that depends on insect pollination, especially squash, cucumbers, and strawberries. It self-seeds prolifically.
Combinations to Avoid
Fennel: The Garden Loner
Fennel inhibits the growth of virtually all vegetables through allelopathy — it releases chemicals from its roots that suppress neighboring plants. Grow fennel in its own isolated container or in a distant corner of the garden.
Black Walnut Proximity
Black walnut trees produce juglone, a compound toxic to many garden plants. Tomatoes, peppers, eggplant, potatoes, and many other vegetables cannot grow within the root zone. If you have black walnut trees, use raised beds with barrier fabric.
Other Problem Combinations
Onions and garlic near beans and peas inhibit legume growth. Potatoes near tomatoes share late blight susceptibility and concentrate pest pressure. Sunflower hulls release allelopathic compounds that can inhibit nearby seedlings. Brassicas near strawberries reportedly reduce berry production.
Companion Planting in Raised Beds and Containers
Companion planting is particularly effective in raised beds and containers where plants grow in close proximity. In a raised bed layout, interplanting herbs and flowers among vegetables creates a diverse, pest-resistant ecosystem in a small space. For container gardens, grow basil in the same pot as tomatoes or peppers.
Making Companion Planting Work
Start Simple
Do not attempt to implement every combination at once. Start with the most well-documented partnerships: basil with tomatoes, marigolds throughout the garden, and alliums near carrots.
Combine With Other Good Practices
Succession planting, crop rotation, healthy soil management through composting, and proper watering remain the foundations. Think of companion planting as an additional layer of insurance.
Frequently Asked Questions
Does companion planting actually work?
Yes, with realistic expectations. The pest-repelling effects of aromatic herbs, the nitrogen fixation of legumes, and the nematode-killing properties of marigolds are well-documented in peer-reviewed research. Expect a meaningful reduction in pest pressure (30 to 50 percent for the best combinations), not complete immunity.
How close do companion plants need to be?
For scent-based pest deterrence, within 2 to 3 feet. Interplanting is more effective than perimeter planting alone. For nitrogen fixation, plant beans within 12 to 18 inches of crops you want to benefit.
Can companion planting replace pesticides?
For many home gardeners, companion planting combined with other organic practices can eliminate the need for any pesticides. For severe infestations, targeted treatments like neem oil may still be needed.
What is the best overall companion plant for a vegetable garden?
French marigolds (Tagetes patula) provide the broadest range of benefits: nematode suppression, aphid and whitefly deterrence, pollinator attraction, and they thrive in every growing zone.
Does companion planting work in containers?
Absolutely. Growing basil in the same pot as tomatoes, placing marigolds near vegetable containers, and using nasturtiums as trap crops all provide meaningful benefits. Container gardens on balconies especially benefit because the concentrated space amplifies both pest pressure and companion effects.
