Companion Planting Chart: 30+ Pairings That Repel Pests, Boost Yields and Should Never Be Grown Together

Every experienced gardener keeps a companion planting chart nearby — not because the rules are hard to learn, but because there are a lot of them. Thirty-plus vegetables, a dozen common herbs and flowers, hundreds of possible pairings. Getting it wrong costs you a season; getting it right can mean 20–30% better yields, far fewer pest problems, and a garden that does some of its own maintenance.

This guide is built around the chart. The color-coded matrix below covers 30 vegetables, herbs, and flowers against 10 key companion categories — scan it before you plan any bed. Below the grid you’ll find a quick-reference best-friends list for the 10 most commonly grown vegetables, a breakdown of why companion pairs work, and an FAQ covering the most common questions. For the full science and planting strategies, see the complete companion planting guide.

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Vegetable	Best Companions	Avoid	Why it works
Tomatoes	Basil, marigolds, carrots, parsley	Fennel, brassicas, potatoes	Basil repels aphids & whitefly; marigolds deter nematodes
Beans	Carrots, squash, corn, radishes	Onions, garlic, fennel	Fixes nitrogen; corn and squash provide shade and structure
Carrots	Onions, leeks, rosemary, tomatoes	Dill (once flowering), parsnips	Onion family deters carrot fly; rosemary masks scent
Cucumbers	Dill, beans, peas, radishes, nasturtiums	Potatoes, sage, strongly aromatic herbs	Nasturtiums trap aphids; beans fix nitrogen for heavy feeders
Potatoes	Horseradish, beans, marigolds, nasturtiums	Tomatoes, squash, cucumbers, fennel	Horseradish deters Colorado beetle; marigolds repel eelworm
Brassicas	Dill, celery, onions, hyssop, nasturtiums	Tomatoes, strawberries, fennel	Nasturtiums lure cabbage white away; dill attracts predatory wasps
Squash	Corn, beans, nasturtiums, borage	Potatoes, fennel	Three Sisters system: corn=trellis, beans=nitrogen, squash=ground cover
Lettuce	Carrots, radishes, chives, strawberries	Fennel, celery (competition)	Tall companions shade lettuce in summer; radishes loosen soil
Onions	Carrots, beets, chamomile, summer savory	Beans, peas, asparagus	Deters carrot fly when interplanted; chamomile improves flavor
Basil	Tomatoes, peppers, asparagus	Sage, common rue	Repels thrips, aphids and whitefly from neighboring nightshades

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How to Use This Companion Planting Chart

The matrix uses a simple traffic-light system. Find your vegetable in the left column (row header), then look across to find your candidate companion in the top row. The color of the intersection cell tells you what to do:

• Green ✓ (Beneficial): Plant these together. One or both plants gain a measurable advantage — better pest resistance, improved pollination, faster growth, or nitrogen enrichment.
• Red ✗ (Avoid): Keep these apart. They compete for the same nutrients, attract shared pests, or produce allelopathic compounds that inhibit each other’s growth.
• Gray — (Neutral): No significant interaction either way. They can share space safely but don’t provide a specific benefit.
• Dot • (Same plant): These are the same plant or family — monocropping considerations apply instead.

The chart covers the intersection of a row plant as the host and a column plant as the companion. Most interactions are reciprocal, but some are not — dill, for example, benefits carrots but can inhibit tomatoes once it flowers.

The Companion Planting Matrix: 30 Plants

The table covers 30 of the most commonly grown food garden plants. Scroll horizontally on small screens. Each intersection shows whether the column plant is a good, bad, or neutral companion for the row plant.

✓ Beneficial✗ Avoid— Neutral• Same plant

Note: Dill is beneficial to carrots and brassicas at all stages, but near tomatoes it should be removed before it flowers — bolted dill produces compounds that can inhibit tomato growth. Young dill is generally neutral to tomatoes. Fennel is antagonistic to almost every garden plant and is best grown in a container or isolated bed.

Best Friends: Quick Reference for the 10 Most Common Vegetables

These condensed profiles give you the top companions and worst enemies for each vegetable at a glance. Use them when planning bed layouts or filling gaps.

1. Tomatoes

Basil is tomato’s most famous partner — see the basil growing guide for varieties suited to companion planting. Marigolds deter nematodes in the soil and repel whiteflies above ground. Keep fennel at least 10ft away. For full detail on what to grow with and near tomatoes, visit the tomato growing guide.

2. Cucumbers

Sunflowers give cucumbers a trellis and attract pollinators essential for fruit set. Radishes planted at the base deter cucumber beetles — pull the radishes once they bolt and leave the tops as a surface mulch. Marigolds suppress soil nematodes that target cucumber roots.

3. Beans (Bush and Pole)

Beans fix atmospheric nitrogen through rhizobacteria in their root nodules — every neighboring plant benefits from the soil enrichment, especially nitrogen-hungry corn. This is why corn, beans, and squash form the legendary Three Sisters trio. Alliums (onions, garlic, chives) produce sulfur compounds that inhibit bean root bacteria, sharply reducing nitrogen fixation.

4. Peppers

Peppers and tomatoes are close relatives and share most of the same companions. Basil planted around the base is said to repel aphids and improve fruit set. Spinach or lettuce as a ground cover under peppers keeps the soil cool and moist — critical for pepper yield in hot summers.

5. Lettuce

Lettuce bolts (goes to seed and turns bitter) when temperatures exceed 75°F. Tall companions — tomatoes, corn, pole beans — provide afternoon shade that delays bolting by 2–3 weeks. Radishes act as a trap crop for flea beetles, drawing them away from lettuce leaves. Strawberries make an excellent ground-cover companion; see the strawberry growing guide for spacing.

6. Carrots

The carrot–onion pairing is one of the most well-documented in companion planting: onion scent masks the carrot from carrot fly (Psila rosae), while carrot scent confuses onion fly. Research from Rothamsted Research station confirmed the masking effect measurably reduces carrot fly damage when the two are interplanted in alternating rows.

You might also find sunflower companion plants helpful here.

7. Brassicas (Broccoli, Cabbage, Kale, Cauliflower)

Brassicas are the most pest-targeted plants in the vegetable garden — aphids, cabbage white caterpillars, and cabbage root fly are constant threats. Dill and nasturtiums attract hoverflies and parasitic wasps that predate aphids. Sage and rosemary produce essential oils that deter cabbage white butterflies from landing to lay eggs.

8. Potatoes

Potatoes share late blight (Phytophthora infestans) and early blight with tomatoes, eggplant, and peppers — never follow or precede these crops in the same bed, and never plant them adjacent. Horseradish planted at the corners of a potato bed is a traditional deterrent for Colorado potato beetles and is supported by several extension service recommendations.

9. Onions and Garlic

Alliums are among the most versatile pest-deterrent plants in the vegetable garden. Their sulfur-rich root exudates and above-ground volatile compounds repel a wide range of insects including aphids, carrot fly, and spider mites. Chamomile planted near onions is reported to improve bulb size — though the mechanism isn’t fully understood, it may relate to calcium mobilization in the root zone.

10. Squash and Zucchini

Squash is the most important member of the Three Sisters trio when it comes to soil health — its enormous leaves create living mulch that suppresses weeds, retains soil moisture, and keeps roots cool. Nasturtiums planted at the edges of the squash bed act as a trap crop for aphids and squash bugs. Borage is another excellent companion, said to deter squash vine borers and improve pollinator visits.

Why Do Companion Pairs Work? The Science Behind the Chart

Companion planting is not folklore. The interactions that make it work fall into four documented categories:

1. Allelopathy (chemical suppression/stimulation). Plants release compounds into the soil through root exudates and leaf litter. Marigolds produce alpha-terthienyl, a compound that kills soil nematodes. Black walnut trees release juglone, which kills tomatoes within root range. Fennel produces allelopathic terpenes that inhibit germination and growth of most neighboring plants — which is why it appears as ✗ throughout the matrix. Conversely, some root exudates stimulate neighbors: legume rhizobacteria release fixed nitrogen that nearby plants absorb directly.

2. Physical structure and microclimate. Tall plants like corn or sunflowers provide shade and wind protection for heat-sensitive crops. Sprawling squash leaves create living mulch. Dense low-growing ground covers like spinach and lettuce keep soil temperature down and moisture in. Pole beans climbing corn require no separate trellis structure.

3. Pest and disease management. This operates through three sub-mechanisms: (a) masking — aromatic herbs like basil, rosemary, and mint produce volatile compounds that make it harder for insects to locate target crops by scent; (b) trap cropping — nasturtiums, radishes, and blue hubbard squash attract pests away from main crops; (c) predator attraction — dill, fennel flowers, and yarrow attract parasitic wasps and hoverflies that predate aphids and caterpillars.

4. Pollinator support. Many vegetables require insect pollination for fruit set — cucumbers, squash, peppers, and tomatoes all produce more fruit when pollinator activity is high. Marigolds, nasturtiums, borage, and phacelia planted nearby dramatically increase bee visits. Borage in particular has been shown to increase bumblebee foraging activity in adjacent vegetable plots.

The Three Sisters: History’s Most Famous Companion Trio

The Three Sisters — corn, beans, and squash — is a Native American polyculture system used for centuries across North America. Its genius lies in how the three plants solve each other’s biggest problems simultaneously. Corn grows tall and provides the trellis structure that pole beans need to climb. Pole beans fix atmospheric nitrogen through root rhizobacteria, feeding the nitrogen-hungry corn without any added fertilizer. Squash spreads along the ground, its large leaves creating a living mulch that retains moisture, suppresses weeds, and keeps soil temperatures stable — benefiting all three plants.

The result is a self-sustaining growing system that requires fewer inputs than growing any of the three crops alone. Research published by Cornell University’s Three Sisters Project showed that the Three Sisters polyculture produced yields equivalent to or greater than monocultures of each crop, while significantly reducing weeding labor and water requirements. To plant your own Three Sisters bed: sow corn first and wait until it reaches 4–6 inches, then sow 4–6 bean seeds around each corn plant, then transplant squash seedlings at the corners of the bed a week later.

Tomato Companion Planting in Practice

Tomatoes have the longest and best-documented companion planting profile of any vegetable. The basil pairing has been studied repeatedly: while formal RCT evidence on flavor enhancement is mixed, multiple studies confirm that basil volatile compounds — particularly linalool and eugenol — measurably reduce aphid and whitefly populations when plants are in close contact. Plant one basil plant for every two tomato plants, spaced 12–18 inches from the tomato stem. Full tomato growing guide covers spacing, support, and variety selection in detail.

Marigolds earn their place in the tomato bed through the root, not the leaf — alpha-terthienyl produced by marigold roots kills root-knot nematodes (Meloidogyne spp.), which are a chronic soil pest in tomato beds. For this to work, marigolds must be grown in the same soil for at least one full season, not just planted nearby. French marigolds (Tagetes patula) are more effective than African marigolds (T. erecta) at nematode control. Plant densely — 1 marigold per square foot throughout the tomato bed — for soil-level protection, and let them decompose in place at the end of the season.

Companion Planting by Goal

Use this quick-reference to choose companions based on the problem you’re trying to solve:

Use our interactive Companion Planting Tool to get personalized results for your garden.

Frequently Asked Questions

Does companion planting actually work, or is it just garden folklore?

Both — depending on which pair you’re asking about. Some companion interactions are well-documented and peer-reviewed: nematode suppression by French marigolds (multiple RCTs), nitrogen fixation by legumes (established biochemistry), pest masking by aromatic herbs (confirmed via olfactometry studies). Others — like tomato flavor improvement from basil — have weak or mixed evidence. The most reliable use of companion planting is for pest management and soil enrichment, not as a replacement for good fertility and water management.

Can I companion plant in raised beds and containers?

Yes, and raised beds are often better for companion planting because you control the soil and can plan pairings precisely. In a 4x8ft raised bed you can easily run a Three Sisters planting (one corner of corn + pole beans + squash), a tomato–basil strip, or a brassica bed with dill and nasturtiums around the edge. Containers work for pairing herbs with vegetables: a pot of basil next to a tomato container provides the same volatile-compound benefit as in-ground planting, provided the pots are within 12–18 inches of each other.

How close do companion plants need to be to work?

It depends on the mechanism. Root interactions (nitrogen fixation, nematode suppression, allelopathy) require plants to be within 6–18 inches of each other — close enough for root zones to overlap. Scent masking works at distances of 12–24 inches, as aromatic compounds disperse in air. Trap cropping works at greater distances — nasturtiums at the bed edge, a few feet away, can draw aphids away from center plants. Pollinator attraction works at the garden scale: a borage plant anywhere in a 20–30ft radius increases bee activity throughout.

What about crop rotation — does it conflict with companion planting?

No — they work on different timescales. Companion planting is a within-season strategy; crop rotation is a year-to-year strategy. In fact, companion planting can support rotation: a legume companion (beans or peas) grown alongside corn in Year 1 leaves the soil nitrogen-enriched for a heavy-feeding crop in Year 2. Plan your rotations by plant family (solanums, brassicas, alliums, legumes, roots) and layer your companion planting on top within each year’s bed assignment.

Why is fennel shown as antagonistic to almost everything?

Fennel (Foeniculum vulgare) produces allelopathic compounds — primarily anethole and fenchone — that inhibit the germination and growth of most neighboring plants. Research has shown fennel root exudates suppress the growth of tomatoes, peppers, beans, and many others by up to 30–60% when plants are within root range. Fennel is not useless in the garden — its flowers are excellent for attracting parasitic wasps — but it must be grown in isolation, ideally in a dedicated pot or a separate bed at least 3ft from other edibles.

Sources

• Cornell University Three Sisters Farming Project — polyculture yield studies and nitrogen cycling data
• Rothamsted Research — carrot fly masking experiments with onion interplanting (published in Annals of Applied Biology)
• UC Davis Integrated Pest Management Program — companion planting and biological control guidelines
• Poveda, K. et al. (2008). “The enemy of my enemy is my friend.” Ecological Applications 18(2): 406–416 — parasitic wasp attraction by aromatic plants
• Hooks, C.R.R. & Johnson, M.W. (2003). “Impact of interplanting with aromatic herbs on aphid populations.” Journal of Economic Entomology 96(4): 1027–1036
• The 7 Best Companion Plants for Gardenias