Companion Planting Chart
Companion planting chart for US vegetable gardens. Find which plants grow better together, which to keep apart, and the evidence behind each pairing.
Key takeaways
- French marigolds (Tagetes patula) suppress root-knot nematodes in soil when planted 12 inches from tomato stems — confirmed by USDA Agricultural Research Service studies
- The Three Sisters system (corn, beans, squash) is the oldest documented US companion planting method, developed by Indigenous peoples and still effective in home gardens
- Fennel is allelopathic to most vegetables — plant it in a container or an isolated bed, not in the main vegetable garden
- Basil improves tomato flavor and repels thrips when planted 18 inches from tomato stems, based on University of Florida research
- Dill attracts beneficial predatory wasps when flowering — plant it near cucumbers and beans but away from carrots, which it can cross with
What is companion planting?
Companion planting means growing two or more plant species close together for mutual benefit. Documented benefits include pest repulsion, soil improvement through nitrogen fixation, physical support (one plant trellising another), and attraction of beneficial insects. Some pairings also reduce growth — which is equally useful information to avoid.
The evidence for companion planting varies by pairing. Some combinations — like marigolds suppressing nematodes and beans fixing nitrogen for corn — are documented in peer-reviewed research. Others are based on generations of gardening observation without controlled studies. This chart distinguishes between the two.
University of California Agriculture and Natural Resources has published meta-analyses on companion planting showing that polyculture plantings (mixing multiple crops) reduce aphid populations by 13–47% compared to monoculture plots. The mechanisms vary: some companions physically block pest access, some release chemicals that repel or confuse pests, and some attract beneficial insects that prey on garden pests.
Master companion planting chart
The table below covers the most common US vegetable garden crops. A ”+” rating means a documented or widely confirmed benefit exists. A ”-” means inhibition or pest-attracting conflict. “Neutral” means no known effect.
| Crop | Good companions | Avoid | Why |
|---|---|---|---|
| Tomatoes | Basil, French marigold, carrot, parsley, asparagus | Fennel, brassicas, corn | Basil repels thrips; marigolds suppress nematodes; brassicas attract shared aphids |
| Peppers | Basil, carrot, tomatoes, parsley | Fennel, brassicas | Shared pest deterrence; brassicas attract aphids that spread to peppers |
| Cucumbers | Beans, dill, nasturtiums, radishes | Sage, aromatic herbs | Beans fix nitrogen; dill attracts predatory wasps; sage inhibits growth |
| Zucchini/squash | Corn, beans, nasturtiums, dill | Potatoes, pumpkin | Three Sisters benefit; potatoes and squash share blight |
| Carrots | Onions, leeks, rosemary, sage | Dill, parsnips | Onion family deters carrot fly; dill can hybridize with carrots |
| Beans | Carrots, cucumbers, squash, marigolds | Onions, garlic, fennel | Alliums inhibit bean growth; marigolds deter Mexican bean beetles |
| Corn | Beans, squash, sunflowers | Tomatoes | Three Sisters; sunflowers attract beneficial insects |
| Lettuce | Carrots, radishes, strawberries, chives | Celery, parsley | Radishes deter leaf miners; chives repel aphids |
| Onions/garlic | Carrots, tomatoes, beets, chamomile | Beans, peas, asparagus | Alliums deter many pests; inhibit legume growth |
| Brassicas | Dill, nasturtiums, hyssop | Tomatoes, strawberries, peppers | Dill and nasturtiums attract beneficial insects; brassicas share aphids with nightshades |
| Strawberries | Lettuce, spinach, borage | Brassicas, fennel | Borage deters hornworms; brassicas compete aggressively |
| Herbs (basil) | Tomatoes, peppers, asparagus | Sage | Deters thrips; improves fruit set anecdotally |
Best companion plants for tomatoes
French marigolds, basil, and carrots are the three most useful tomato companions backed by research. Marigolds suppress soil nematodes, basil deters thrips and whiteflies, and carrots aerate the soil around tomato roots when interplanted at 6-inch spacing.
Marigolds and tomatoes
Plant French marigolds (Tagetes patula) — not African marigolds — 12 inches from tomato stems throughout the bed and as a border. Plant them at the same time as tomatoes or two weeks earlier so they are established when tomato roots begin spreading.
Research from the USDA Agricultural Research Service found that beds with French marigold borders had 30–50% lower root-knot nematode populations at season end compared to control beds. The effect builds over multiple seasons as marigold root exudates accumulate in soil.
Marigolds also attract hoverflies and parasitic wasps that prey on aphids and caterpillar eggs. A border of marigolds around a tomato bed provides multiple overlapping pest-control functions.
Basil and tomatoes
Plant basil 18 inches from tomato stems to avoid competing for root space. Research from the University of Florida found that basil planted near tomatoes reduced thrip populations by 27% compared to tomatoes grown alone. Thrips damage tomato flowers and reduce fruit set, so this is a meaningful benefit in affected regions.
Basil and tomatoes also share the same growing conditions — full sun, consistent moisture, and warm temperatures — so interplanting doesn’t require managing conflicting care requirements.
For detailed tomato care including how to incorporate companions into your planting plan, see our how to grow tomatoes guide and tomato companion plants for the complete list.
Best companion plants for peppers
Basil, carrot, and parsley are the most reliable pepper companions. Basil deters aphids and thrips that commonly attack peppers; carrots and parsley attract parasitic wasps that target pepper weevils and aphid predators.
Peppers and tomatoes are closely related (both nightshades) and share most of the same companion preferences. The main difference: peppers are more sensitive to root competition. Plant companions at least 18 inches from pepper stems.
Keep fennel away from peppers. Fennel releases allelopathic compounds from its roots that inhibit growth in most vegetables including peppers. Even companion-friendly fennel varieties have this effect within 2–3 feet.
For more on pepper growing and care, see companion plants for peppers.
Best companion plants for cucumbers
Beans, dill, and nasturtiums are the most effective cucumber companions. Beans fix atmospheric nitrogen that cucumbers use heavily for vine growth; dill attracts parasitic wasps; nasturtiums act as a trap crop for aphids and attract cucumber-foraging beneficial insects.
Plant pole beans and cucumbers on the same trellis or fence — they share the same vertical space without competing. Both need consistent moisture and benefit from the same watering schedule.
Dill is most effective when allowed to flower. Flowering dill releases nectar that attracts predatory wasps and hoverflies that parasitize aphids and cucumber beetle eggs. Trim dill flowers once seed begins setting to prevent dill from overtaking the bed — it self-seeds prolifically.
Radishes planted alongside cucumbers repel cucumber beetles when young (before radishes bolt). Pull radishes when they flower; flowering radishes do not deter pests and crowd root space.
See our cucumber trellis guide and growing cucumbers guide for care details.
Best companion plants for carrots
Onions, leeks, and rosemary are the most reliable carrot companions. The sulfur compounds in onion family plants confuse carrot flies (Psila rosae), which locate host plants by scent. Interplanting onions and carrots in alternating rows reduces carrot fly infestation by 40–60% in UK Ministry of Agriculture trials.
This effect applies across the US where carrot fly is present, primarily in the Pacific Northwest and Northeast. In the South and Midwest, where carrot fly is less common, the benefit is less pronounced but rosemary still deters the few carrot pests present.
Do not plant dill near carrots. Dill and carrots are in the same plant family (Apiaceae). They can cross-pollinate and hybridize, producing off-type seeds if you are saving seed. Even if you are not seed-saving, dill roots compete aggressively with carrot roots and reduce carrot yields in the same bed.
For companion planting details specifically for carrots, see companion plants for carrots.
Best companion plants for beans
Carrots, cucumbers, and squash are the best bean companions. Beans fix atmospheric nitrogen — 50–200 pounds per acre per season in ideal conditions — which feeds nitrogen-demanding crops. Marigolds deter Mexican bean beetles when planted in the border.
Beans as companions: beans benefit almost every other crop in the garden by fixing nitrogen. When you pull spent bean plants at the end of the season, leave the roots in the soil — they hold the nitrogen nodules that release fixed nitrogen as they decompose.
What to avoid near beans: onions, garlic, and all alliums inhibit bean germination and growth. Keep any allium family crop at least 24 inches from beans. Fennel is also incompatible — keep it 3 feet away or out of the bed entirely.
See our bean companion plants guide for the full list.
Best companion plants for strawberries
Borage, spinach, and lettuce are reliable strawberry companions. Borage deters tomato hornworms (which also affect strawberries), and its flowers attract pollinators that improve strawberry fruit set by 10–15% in garden trials.
Keep brassicas away from strawberries. Brassicas and strawberries compete intensely for soil resources and the brassicas almost always win, reducing strawberry runners and overall yield.
Onion family plants also inhibit strawberry growth. Keep garlic and onions at least 3 feet from strawberry beds.
For more on strawberry growing, see strawberry companion plants.
The Three Sisters — the original US companion planting method
The Three Sisters method — corn, beans, and squash planted together — was developed by Indigenous peoples of North America and is the oldest documented companion planting system in the US. The three crops provide mutual support: corn supplies a trellis for beans, beans fix nitrogen for corn and squash, and squash leaves shade the soil to retain moisture and suppress weeds.
Planting the Three Sisters:
- Plant corn first, in hills 12–18 inches apart in a grid pattern (not rows)
- When corn is 6 inches tall, plant 4–6 bean seeds around each corn stalk in a circle 6 inches out
- When beans have sprouted, plant 2–3 squash seeds between the corn hills
This method works because each crop fills a different niche. Corn grows vertically, beans grow up the corn, and squash spreads horizontally across the ground. Nitrogen fixed by beans feeds the corn’s high nitrogen demand.
The Three Sisters system produces a higher combined yield per square foot than any of the three crops grown separately in monoculture. University of Illinois Extension documented a 20% higher combined caloric yield from Three Sisters plots compared to equivalent monoculture area.
Plants that should not grow together
Some plants actively inhibit each other. This is called allelopathy — chemical inhibition of neighboring plants through root exudates or leaf decomposition.
| Plant | Inhibits | Mechanism |
|---|---|---|
| Fennel | Most vegetables, especially tomatoes, peppers, beans | Root exudates inhibit germination and growth |
| Black walnut | Tomatoes, potatoes, most vegetables | Juglone toxin released from roots extends 50–80 feet |
| Brassicas | Strawberries, tomatoes | Competitive root systems; shared aphid populations |
| Garlic/onions | Beans, peas | Allium compounds inhibit legume germination |
| Sage | Cucumbers, onions | Essential oils inhibit growth at close range |
Keep fennel in a container or an isolated corner of the yard. Its allelopathic effect persists in soil for months after the plant is removed.
Black walnut is the most powerful natural plant inhibitor in US gardens. Do not plant vegetables within 50–80 feet of a black walnut tree. The juglone toxin affects tomatoes most severely — they wilt and die within two seasons if planted in juglone-affected soil.
For related companion planting guides, see companion plants for peppers, zucchini companion plants, and our herb garden guide for which herbs to use as companions throughout the vegetable garden.
Sarah Mitchell is a Master Gardener and garden writer based in the Pacific Northwest. She has been growing food and flowers for over 15 years across USDA zones 7 and 8.