by Bethany Hayes (revised and updated)
The 30-second version: Companion planting really can help your tomatoes — but I’ll be honest with you, not every old garden pairing holds up. The pairings I trust most are using a hairy vetch cover crop to fight early blight and Septoria leaf spot, planting French marigolds to knock back root-knot nematodes in the soil, and using trap crops and flowers to pull pests away and bring the good bugs in. A few classics (basil “repels hornworms,” borage “improves flavor”) are popular tradition more than proven fact, and I’ll tell you which is which as we go. Here are the 26 plants I’d grow near tomatoes — grouped by what they actually do — plus the 5 I keep far away.
Do These Things First
Before we get into specific plants, here are a few basics I always keep in mind, no matter what I’m planting:
- Give every plant room to breathe. A lot of companion planting’s real disease benefit comes down to spacing and airflow, not magic. Crowded, damp leaves are exactly what fungal diseases love.
- Let your herbs flower. Many of the best companions — dill, cilantro, oregano, sweet alyssum, parsley — only do their job once they bloom and start feeding beneficial insects. I always let a few go to flower.
- Treat trap crops as sacrificial. They work by being tastier to a pest than your tomatoes, so plant them somewhere you’re okay losing them.
- Don’t expect one plant to fix everything. Companion planting is just one layer of a healthy garden, right alongside consistent watering, crop rotation, and mulch.
Now let’s get into it.
What Companion Planting Can (and Can’t) Do
Companion planting is just growing certain plants near each other for a benefit — repelling pests, attracting pollinators and predatory insects, improving the soil, or filling space that weeds would otherwise grab.
Gardeners and farmers have been pairing plants this way for generations, and some of those pairings really are backed by research now. But I’ll level with you: a lot of companion-planting advice floating around online is repeated tradition that’s never actually been tested, and some of it is just plain wrong. So in this guide I’ve separated the two. Where there’s solid evidence, I’ll say so. Where a pairing is more tradition or anecdote, I’ll tell you that too, so you can decide what’s worth your precious garden space.
The good news? Tomatoes are easygoing neighbors. Most plants get along with them just fine, so you’ve got plenty of great options — and only a short list to steer clear of.
Quick Reference: 26 Companions at a Glance
Save or screenshot this one — it’s the cheat sheet.
| Plant | Main benefit | Evidence |
|---|---|---|
| Hairy vetch | Cover crop that reduces early blight & Septoria leaf spot; adds nitrogen | Strong |
| Marigolds (French) | Suppress root-knot nematodes in soil | Strong |
| Crimson clover | Living mulch; adds nitrogen; attracts beneficial insects | Strong |
| Winter rye | Cover crop; smothers weeds; protects soil | Strong |
| Oats | Cover crop; suppresses weeds | Strong |
| Sweet alyssum | Feeds parasitic wasps & hover flies | Strong |
| Dill | Attracts parasitic wasps & other beneficials (let it flower) | Good |
| Cilantro | Flowers feed predatory insects | Good |
| Parsley | Attracts hover flies | Good |
| Nasturtiums | Trap crop for aphids | Good |
| Radish | Trap crop for flea beetles | Good |
| Collard greens | Trap crop for harlequin bugs | Good |
| Sunflowers | Attract pollinators & beneficial insects | Good |
| Coneflowers | Attract pollinators | Good |
| Borage | Attracts pollinators (flavor claim is folklore) | Good |
| Amaranth | Attracts predatory insects; some shade | Moderate |
| Oregano | Flowers feed beneficial insects | Moderate |
| Thyme | Living ground cover; may reduce some pest egg-laying | Moderate |
| Basil | Pollinator/beneficial draw; pest-repel claim is weak | Mixed |
| Bush beans | Adds nitrogen; spacing aids airflow | Moderate |
| Cowpeas | Trap crop for stink bugs | Moderate |
| Lettuce | Fills space; living ground cover | Moderate |
| Sweet potatoes | Ground cover reduces soil splash | Moderate |
| Cucumbers | Pollinator draw; ground-level weed cover | Moderate |
| Carrots | Space-filler (soil-aeration claim is weak) | Weak |
| Celery | Space-filler (soil-loosening claim is weak) | Weak |
Now let me group them by what they actually do for your tomatoes.
Pest-Fighters and Trap Crops
Nasturtiums — trap crop for aphids
Nasturtiums are one of the most popular edible flowers, and they’re a classic trap crop. Aphids love them, so a ring of nasturtiums pulls the aphids off your tomatoes and concentrates them where you can deal with them. Just think of the nasturtiums as sacrificial — and enjoy the flowers in your salads as a bonus.
Radish — trap crop for flea beetles
I love radishes; they’re so underrated. Radishes lure flea beetles away from tomatoes because the beetles would much rather chew radish leaves. Plant them right next to your tomatoes, especially to protect young seedlings, which suffer the most from flea beetles.
Collard greens — trap crop for harlequin bugs
Are harlequin bugs a problem where you garden? Collard greens make an excellent sacrificial trap crop. Harlequin bugs favor cabbage-family plants, so they’ll head straight for the collards instead of your tomatoes. You won’t get to eat those collards, but you’ll save your tomatoes — I’ll take that trade.
Cowpeas — trap crop for stink bugs
Cowpeas draw green stink bugs — a common Southern pest nobody likes to handle — away from your tomatoes. Plant them a few feet from your tomatoes and a few weeks earlier, so they’re already attractive by the time your tomatoes are setting fruit.
Marigolds — they suppress root-knot nematodes
Marigolds absolutely earn their reputation, but for a specific reason: French marigolds (Tagetes patula) suppress root-knot nematodes — those microscopic soil pests that attack tomato roots. The marigold roots release compounds that interfere with the nematodes’ life cycle, and the effect is strongest when you grow marigolds densely as a cover crop and work them into the bed before planting, not just dot a few around the border. They’re cheerful, easy, and one of the few plants with real soil-pest science behind them.
Thyme — living ground cover
Thyme forms a low living mulch around your tomatoes, and some studies suggest interplanting it can reduce egg-laying by certain pests like armyworms. The evidence is only moderate, so I think of thyme as a handy ground cover with a possible pest bonus. One thing to remember: thyme is a perennial and tomatoes aren’t, so you’ll be working around established thyme each season.
Basil — I love it, but the pest claim is weak
Basil is the most famous tomato companion of all, and that flavor pairing is hard to beat. But I have to be straight with you: the common claim that basil “repels hornworms and thrips” has thin scientific support. What basil reliably does is flower and bring in pollinators and beneficial insects, and some growers do report a little yield bump. So grow it because it’s wonderful in the kitchen and feeds the good bugs — just don’t count on it as your pest control.
Pollinator and Beneficial-Insect Attractors
These plants earn their keep by feeding the good bugs — pollinators that improve fruit set, and the predatory and parasitic insects that eat your tomato pests. Most of them only work once you let them flower, so resist the urge to harvest every last leaf.
Dill — attracts parasitic wasps
Dill is one of the better-supported herb companions. Its flowers attract parasitic wasps, which lay their eggs right in tomato hornworms, fruitworms, and other caterpillars — and many of the worst pests in the garden are caterpillars! It also brings in ladybugs, lacewings, and hover flies. One nuance worth knowing: young dill grows happily alongside tomatoes, but mature, flowering dill can compete with and slightly stunt nearby tomatoes, so give it a little space rather than planting it right on top of them.
Cilantro — its flowers feed predators
Humans might argue about whether cilantro tastes amazing or like soap, but the beneficial insects have no doubt about it. Cilantro blooms are a nectar source for the predatory insects that eat tomato pests, so let a few plants bolt and flower instead of harvesting them all.
Parsley — attracts hover flies
Parsley draws hover flies, whose larvae feast on aphids and other soft-bodied pests. Like the other herbs here, it does the most good once you let it flower, so tuck a little throughout your beds.
Oregano — let it bloom
Oregano tastes perfect with tomatoes and, once it flowers, attracts pest-eating beneficial insects. Here’s what I do: I keep a couple of plants trimmed for the kitchen and let a couple go to flower for the bugs. Best of both worlds.
Sweet alyssum — feeds the tiny beneficials
Sweet alyssum is best known for boosting biological control in lettuce, but those little white flowers also feed parasitic wasps and syrphid (hover) flies in the tomato patch.
Borage — a pollinator magnet (but the flavor claim is folklore)
Borage is fantastic at pulling in pollinators, which can help your tomatoes set fruit. But the much-repeated claims that borage “improves tomato flavor” and “repels hornworms”? Those are traditional folklore without solid evidence. Grow it for the pollinators and the pretty edible flowers — just don’t expect tastier tomatoes out of the deal.
Sunflowers — a pollinator draw
Sunflowers are lovely in any garden, and they bring in bumblebees and other pollinators to boost pollination nearby. Just plant them where they won’t shade your tomatoes for most of the day.
Coneflowers — another pollinator draw
Coneflowers (echinacea) have big, open blooms that bumblebees adore — and they’re beautiful and useful in their own right, so they’re an easy yes.
Amaranth — habitat for predatory insects
Amaranth is an edible grain you can grow right in your garden, and it attracts predatory insects while throwing a little shade. Useful, though the evidence is more moderate than for the flowering herbs above.
Cover Crops and Living Mulch
Here’s where companion planting has some of its strongest research behind it — using cover crops to feed the soil, smother weeds, and even cut down on disease.
Hairy vetch — the standout for disease
Never heard of hairy vetch? You’re not alone — but if you fight early blight or Septoria leaf spot, this is the best-documented companion on the whole list. USDA research found that growing tomatoes into a killed hairy-vetch mulch reduced foliar disease compared with bare soil or black plastic. Plant it in fall, cut it down by hand when the first seed pods show up in late spring, and transplant your tomatoes right into the residue. As a legume it also fixes nitrogen, and the mat suppresses weeds. Hard to beat.
Crimson clover — living mulch and nitrogen
Crimson clover makes a wonderful living mulch between tomato rows. It competes with weeds, fixes nitrogen, and its flowers bring in beneficial insects and pollinators. Let it grow the whole season.
Oats — an easy first cover crop
If you’ve never grown a cover crop, start with oats. Plant them in fall; in cold climates they winter-kill and leave a protective mat you can transplant your tomatoes into come spring. Natural weed control with almost no effort.
Winter rye — the weed smotherer
Winter rye is a cover crop that smothers weeds and protects your soil. Most gardeners grow it over winter and mow it down in spring before transplanting. One heads-up: rye residue can briefly suppress small seeds, so transplant your tomatoes into it rather than direct-seeding anything.
Space-Fillers and Ground Cover
These plants are mostly about using empty space well — shading out weeds, protecting the soil, or earning you a second harvest. The benefits are real but modest, and I want to flag a couple of traditional claims that don’t hold up.
Bush beans — airflow and a little nitrogen
Tucking bush beans between your taller tomatoes keeps everything well spaced (better airflow, fewer fungal headaches), and as legumes they add a bit of nitrogen. Honestly, any short crop gives you that spacing benefit — beans just give you dinner too.
Lettuce — fills space and holds moisture
Lettuce slips right into the gaps between tomatoes, shades the soil to cut down on erosion and moisture swings, and actually loves the light shade your tomatoes cast over it. So you get a great lettuce harvest on top of everything else.
Sweet potatoes — they cut down on soil splash
Sweet potatoes form a thick ground cover, and that matters more than you’d think. A lot of tomato diseases spread when rain splashes soil-borne spores up onto the lower leaves, and a living cover knocks that splash way down. Just give both plants enough room so they aren’t fighting hard for nutrients.
Cucumbers — pollinator draw and ground cover
Cucumbers can grow near tomatoes — their blooms pull in pollinators, and bush types help shade out weeds. One caution: cucumbers release growth-inhibiting compounds that can hurt seeds sown nearby. This works because your tomatoes are transplants, not direct-seeded, so they sail right past that problem.
Carrots and celery — fine to grow, but skip the soil myths
Carrots and celery are perfectly fine to grow near tomatoes as space-fillers, and I do it all the time. But I have to be honest about the popular claims — that carrot roots meaningfully “aerate the soil” for tomatoes, or that celery “loosens the soil and brings up nutrients.” Those are weak and not well supported. One season of carrot or celery roots just doesn’t reshape the soil for the plants next door. Grow them because you want carrots and celery, not as a soil treatment.
5 Tomato Companion Plants to Keep Away
Like I said, more plants work as companions than not — but a few really do make bad neighbors, so it’s worth knowing who to keep away from your tomatoes when you’re planning the garden.
1. Brassicas (the cabbage family)
Cabbage-family plants like cabbage, broccoli, and cauliflower are heavy feeders that compete with tomatoes for the same nutrients and space. (You’ll sometimes read that brassicas chemically “inhibit” tomato growth — the more accurate, agreed-on reason to keep them apart is plain old competition.) Give them their own bed.
2. Corn
Corn and tomatoes are another no-no, and here’s the real reason: the corn earworm and the tomato fruitworm are the same insect (Helicoverpa zea). Plant them side by side and you’ve handed that pest two of its favorite foods in one spot. Keep them well apart.
3. Fennel
Fennel is one of those plants almost nothing wants to grow near, because it releases substances from its roots that stunt nearby plants — tomatoes included. It’s a poor neighbor for just about everything, so give it its own corner or a container.
4. Other nightshades
Tomatoes are in the nightshade family, and so are eggplants, peppers, and potatoes. They all share diseases like early and late blight, which build up in the soil and get worse every year. Grouping them just concentrates that disease pressure — and makes crop rotation harder. Potatoes are an especially bad neighbor.
5. Walnuts (especially black walnut)
Don’t plant tomatoes under or near black walnut trees. Their roots, leaves, and hulls contain juglone, a compound that’s toxic to tomatoes and all nightshades — it can wilt and kill them outright. Keep your tomatoes well outside the tree’s root zone.
Common Questions
Does companion planting really work, or is it a myth?
Both, honestly, depending on the pairing. Cover crops (hairy vetch, clover, rye), trap crops (nasturtiums, radish), nematode-fighting French marigolds, and flowering plants that feed beneficial insects all have real evidence behind them. A lot of the flavor- and scent-based “repellent” claims are tradition and unproven. Use the evidence column in the table above as your guide.
What’s the single best companion plant for tomatoes?
For disease, a killed hairy-vetch mulch has the strongest research behind it. For soil pests, French marigolds grown densely. For pollination and general pest control, any flowering herb — dill, cilantro, sweet alyssum — that you let bloom.
Will basil actually keep hornworms off my tomatoes?
Probably not on its own — that claim is weak. Basil is still worth growing for the kitchen and because its flowers feed beneficial insects. For hornworms, hand-picking and attracting parasitic wasps (with dill and other flowers) work far better.
Can I plant tomatoes and peppers together since they’re both nightshades?
Better not to. They share blight and other soil-borne diseases, so keeping them apart — and rotating where each one goes year to year — really cuts down on disease building up.
How close is too close for corn and tomatoes?
Since they share the corn earworm/tomato fruitworm, give them as much room as your garden allows — ideally different beds or opposite ends of the garden.
Final Thoughts
You’ve got plenty of good tomato companions to choose from — and now a clearer sense of which ones the research actually backs up and which are just garden tradition. Lean on the proven performers (cover crops, trap crops, French marigolds, and flowering herbs that feed the good bugs), enjoy your herbs and flowers for everything else they bring, and keep brassicas, corn, fennel, other nightshades, and walnuts at a safe distance. Your tomatoes will thank you.
