Growing an organic vegetable garden is so much easier when your plants are working together. Companion planting — the practice of strategically placing plants near each other for mutual benefit — is one of the most powerful tools in any organic gardener’s toolkit. This guide covers the best companion plants for vegetables, a quick-reference pairing chart, plants to keep apart, and real tips from years of gardening in Iowa.

What Is Companion Planting (And Does It Actually Work)?

Companion planting is the intentional pairing of plants that benefit each other when grown in close proximity. Those benefits can take several forms:

• Flavor enhancement — some gardeners swear that planting basil near tomatoes improves the flavor of the fruit
• Pest deterrence — some plants repel specific insects through scent or chemical compounds in their roots or leaves
• Attracting beneficial insects — predatory wasps, lacewings, and pollinators that keep pest populations in check
• Improving soil health — certain plants (especially legumes) fix nitrogen, enriching the soil for their neighbors
• Weed suppression — low-growing plants shade the soil and crowd out weeds

Does the science always back up companion planting?

Sometimes yes, sometimes it’s more anecdotal — but after years of companion planting in my own 2,400-square-foot garden, I can tell you that the results are real enough that I wouldn’t garden any other way. The radish-cucumber combination alone has saved my cucumber crop more than once. (More on that below.)

If you’re new to planning your garden layout, grab my free garden planner printable — it’s a great place to map out your companion plant groupings before you put anything in the ground.

Companion Planting Quick-Reference Chart

Use this chart as a starting point. Full details on each plant are below.

Vegetable	Good Companions	Avoid
Tomatoes	Basil, marigolds, carrots, parsley, zinnias	Fennel, brassicas, corn
Cucumbers	Radishes, nasturtiums, dill, sunflowers, marigolds	Sage, potatoes
Peppers	Basil, carrots, marigolds, parsley	Fennel, brassicas
Squash/Zucchini	Nasturtiums, marigolds, corn, beans (Three Sisters)	Potatoes
Cabbage & Brassicas	Dill, rosemary, sage, nasturtiums, thyme	Tomatoes, strawberries
Potatoes	Horseradish, beans, marigolds	Tomatoes, cucumbers, sunflowers
Onions & Garlic	Arugula, carrots, chamomile	Beans, peas
Beans	Marigolds, squash, corn, radishes	Onions, garlic, fennel
Corn	Sunflowers, beans, squash	Tomatoes
Carrots	Sage, rosemary, chives, leeks	Dill, fennel

Herb Companion Plants

Herbs are the workhorses of the companion planting world. Even if you never cook with fresh herbs (though you really should — fresh dill pickles alone are worth it!), planting herbs throughout your vegetable garden delivers real pest-control benefits all season long.

Basil

Basil is one of the most popular companion plants for tomatoes, and for good reason. It’s known to repel thrips and tomato hornworms, and many gardeners — myself included — believe it enhances the flavor of nearby crops.

Best placed near: tomatoes, peppers
Tip: Don’t plant basil in the middle of your tomato patch — as the tomatoes grow, basil gets shaded out and crowded. Plant it along the edges of your tomato area where it gets full sun and stays accessible for harvest.

If tomato hornworms are already a problem for you, check out my guide on how to get rid of tomato hornworms naturally — companion planting helps prevent them, but you may need backup strategies mid-season.

Dill

Dill is a powerhouse for attracting beneficial insects — parasitic wasps, praying mantises, spiders, and beautiful swallowtail butterflies all love it. Those parasitic wasps are particularly valuable because they prey on cabbage caterpillars and aphids. Dill also self-seeds freely, so once you plant it, it tends to come back year after year.

Best placed near: cabbage, cucumbers, onions
Avoid near: carrots and tomatoes (dill can stunt their growth once it goes to seed)

Rosemary

Rosemary is a strong-scented herb that confuses and deters cabbage moths, bean beetles, and carrot flies. It’s also a perennial in warmer climates (though I overwinter mine in a pot here in Iowa), so it’s a long-term garden investment.

Best placed near: cabbage, beans, carrots, sage
Note: If you’re in zone 5 like me, plan to buy rosemary plants each spring or overwinter them indoors.

Sage

Sage deters cabbage moths and carrot flies and is said to improve the health of nearby tomato plants. It also makes a gorgeous edible plant in its own right. I grow it in my cabbage area and along the border of my tomato beds.

Best placed near: cabbage, carrots, tomatoes
Avoid near: cucumbers and onions

Thyme

Thyme is an underrated companion plant that repels cabbage worms, whiteflies, and aphids. It also attracts beneficial insects and, as a low-growing plant, helps suppress weeds when planted as a border. Thyme is hardy and drought-tolerant, making it low-maintenance once established.

Best placed near: cabbage, broccoli, Brussels sprouts, roses
Bonus: Growing Brussels sprouts is a lot easier with thyme nearby to deter cabbage worms.

Chamomile

Chamomile is sometimes called “the plant doctor” because it’s believed to improve the health and flavor of plants growing nearby. It attracts beneficial wasps and hoverflies that prey on aphids, and it accumulates calcium, potassium, and sulfur in its leaves — releasing those nutrients back into the soil as it decomposes.

Best placed near: onions, brassicas, most vegetables in small amounts
Note: Don’t plant chamomile in large quantities throughout the garden — a little goes a long way.

Parsley

Parsley attracts predatory insects including beneficial wasps and hoverflies. It also attracts swallowtail butterfly caterpillars, so if you want those beautiful butterflies in your garden, let some parsley go to seed. Plant it near tomatoes and peppers.

Best placed near: tomatoes, peppers, asparagus
Avoid near: onions and garlic

Herbs make fabulous companion plants. Even if you don’t want to cook with fresh herbs (BUT WHY?!), I highly recommend that you plant them in your garden. Here are some of my favorites.

Basil – repels thrips and tomato hornworm. Enhances the flavor of post garden crops. I’ve always planted it near my tomatoes, but have noticed that it tends to get overshadowed and lost in the tomato growth as the season continues. I will plant basil on the outside of my tomato area, and not in the middle like I did last year. I’ll buy plants for these purposes, though I should start them myself!

Dill – attracts beneficial wasps to help control cabbage moths. Attracts butterflies, praying mantises, and spiders. Plus, I need dill to make my grandma’s famous dill pickles. I’m planting in my cabbage plot, mixed in with the cucumbers, and also mixed in with basil near the tomato area.

Rosemary – repels cabbage moths! I’m also planting rosemary in my cabbage area. I’ll buy rosemary plants as I didn’t start any.

Sage – deters cabbage moths and improves tomato plants. Sage will also go in my cabbage area and outside my tomato plot. I’ll buy sage plants too.

Flowers Companion Plants

Flowers don’t just make the garden prettier — they do serious work keeping pests in check and drawing in pollinators. I think of them as a low-effort, high-reward companion planting strategy. Scatter them throughout your garden beds rather than keeping them confined to a separate flower area.

Marigolds

Marigolds are probably the most well-known companion plant, and they absolutely earn that reputation. French marigolds in particular produce a substance from their roots that repels nematodes in the soil. Above ground, their strong scent deters aphids, bean beetles, squash bugs, and whiteflies. They also attract beneficial predatory insects.

Best placed near: tomatoes, peppers, cucumbers, potatoes, beans
Tip: For nematode control, you need to plant marigolds densely and let them grow for a full season — a few scattered plants won’t have the same effect. I start mine from seed indoors and transplant them around my potato and cucumber beds.

Nasturtiums

Nasturtiums are one of my absolute favorite companion plants. They act as a “trap crop” — aphids, cucumber beetles, and whiteflies are so attracted to nasturtiums that they flock to them and leave your vegetables alone. You can then remove and destroy the nasturtium plants (with the pests on them) before the infestation spreads.

They also repel squash bugs and cabbage moths and attract predatory insects that feed on pests.

Best placed near: cucumbers, tomatoes, squash, cabbage, pumpkins
Bonus: Nasturtium flowers and leaves are edible — peppery and delicious in salads!

If squash bugs are a persistent problem, nasturtiums help but you may also want to read my dedicated guide on preventing squash bugs naturally.

Zinnias

Zinnias attract predatory wasps that target tomato hornworms, and they’re well known for drawing hummingbirds and butterflies. They also reportedly deter cucumber beetles. Beyond their pest benefits, zinnias are one of the easiest flowers to grow from seed, and they bloom all summer long with very little attention.

Best placed near: cucumbers, tomatoes
Tip: Direct sow zinnia seeds after your last frost — they grow quickly and don’t love being transplanted.

Sunflowers

Sunflowers pull double duty as companion plants: they act as a natural trellis for cucumbers and pole beans to climb, and their blooms attract pollinators and beneficial insects. They also provide dappled shade for heat-sensitive crops during the hottest part of summer.

Best placed near: cucumbers, corn, beans
Note: There’s some debate about sunflowers near potatoes — some sources say they compete too much, others say filtered shade from the south side is beneficial. I’ve experimented both ways and lean toward keeping them away from potatoes.

Borage

Borage is an underused gem of a companion plant. It deters tomato hornworms and cabbage worms, attracts bumblebees, and is said to improve the growth and flavor of tomatoes and strawberries. Like nasturtiums, it’s edible — the star-shaped blue flowers are lovely in salads. Borage self-seeds aggressively once established, so plant it where you’re okay with it returning each year.

Best placed near: tomatoes, strawberries, squash
How to grow: Direct sow outdoors after the last frost date.

Lavender

Lavender’s intense fragrance repels fleas, moths, and mosquitoes, and it attracts pollinators from early summer through fall. It’s a perennial in most zones and looks beautiful as a garden border. In zone 5, protect it with winter mulch.

Best placed near: most vegetables, especially brassicas; also great as a border plant
Tip: Lavender prefers well-drained, slightly alkaline soil — avoid planting it in heavy clay.

Vegetable Companion Plants

Vegetables pair well with each other too, not just with flowers and herbs. Here are the most effective vegetable-to-vegetable companion combinations I use in my garden.

Radishes with Cucumbers

This is the companion planting combination that changed my gardening life. I lost my cucumber crop to cucumber beetles three years in a row before I tried planting radishes alongside them. Since I started interplanting radishes directly in my cucumber bed and letting them go to seed, cucumber beetle damage has dropped dramatically.

Plant radish seeds at the same time as cucumbers. Let the radishes go to seed rather than harvesting them — their flowers and seed heads continue working as deterrents.

Also pairs well with: squash, beans

Corn, Beans & Squash — The Three Sisters

The Three Sisters is the ultimate vegetable companion planting combination, developed by Indigenous farmers of North America centuries ago. Corn provides a trellis for beans to climb. Beans fix nitrogen in the soil, feeding the heavy-feeding corn and squash. Squash spreads along the ground, shading out weeds and retaining soil moisture.

Together they create a nearly self-sustaining system. I’ve written a full guide on how to grow a Three Sisters garden — complete with layout tips, planting timing, and what varieties work best.

Arugula with Onions

Planting arugula between onion rows shades the soil, which helps suppress weeds. If you’ve ever spent a summer afternoon hand-weeding between onion sets, you’ll appreciate this one deeply. The arugula grows quickly, stays low, and doesn’t compete significantly with onions for nutrients.

Tip: Arugula can bolt quickly in heat — plant it in spring while temperatures are still cool, or in late summer for a fall crop.

Carrots and Leeks (or Onions)

Carrots deter onion fly; leeks (and onions) deter carrot fly. Planting them together is a classic case of mutual protection. The interplanting confuses the pest insects who locate host plants primarily by scent — mixing the two makes it harder for each pest to find its preferred host.

Horseradish with Potatoes

Horseradish is said to improve the disease resistance of potatoes and may deter Colorado potato beetles. Plant it at the corners of your potato patch — it spreads aggressively so you don’t want it in the middle of the bed.

Related: See my no-dig potato growing guide for an easy method that works great with companion planting.

Beans with Potatoes

Beans deter the Mexican bean beetle when grown with potatoes, and potatoes deter Mexican bean beetles that would otherwise attack beans. Another mutual-protection pairing worth trying.

Plants That Should NOT Grow Together

Companion planting isn’t just about what grows well together — it’s also about knowing what to keep apart. Some combinations actively inhibit growth, share diseases, or attract the same pests.

Keep These Apart	Why
Tomatoes + fennel	Fennel is allelopathic — it releases chemicals that inhibit many plants, especially tomatoes
Tomatoes + brassicas	They compete heavily and share some pests
Onions/garlic + beans or peas	Alliums inhibit the growth of legumes
Cucumbers + sage	Sage is said to stunt cucumber growth
Dill (mature) + tomatoes	Young dill is fine near tomatoes; once it flowers and goes to seed, it can harm tomato plants
Potatoes + tomatoes	Both are nightshades and share diseases like blight — keep them separated
Potatoes + cucumbers	Competition for nutrients and water
Fennel + almost everything	Keep fennel in its own dedicated corner of the garden; it inhibits most vegetables
Sunflowers + potatoes	Sunflowers may compete too aggressively
Brassicas + strawberries	Both are susceptible to the same fungal diseases

How to Actually Use Companion Plants in Your Garden

Knowing which plants pair well is only half the battle — here’s how to put it into practice:

1. Plan on paper first. Map out your vegetable beds and add companion plants at the edges, in between rows, or interspersed throughout. My free garden planner printable makes this easy.

2. Think in layers. Tall plants (sunflowers, corn) provide trellising and shade. Medium plants (tomatoes, squash) form the main crop. Low growers (marigolds, thyme, arugula) fill in gaps and suppress weeds.

3. Prioritize your biggest pest problems. If cucumber beetles devastated you last year, focus on radishes, nasturtiums, and marigolds around cucumbers. If hornworms were your nemesis, load up on basil, dill, and zinnias near tomatoes.

4. Start seeds for companion plants indoors. Marigolds, zinnias, and basil all benefit from an early start. See my guide to starting seeds indoors for timing and tips.

5. Let some plants go to seed. Radishes and dill are especially effective once they flower and go to seed. Resist the urge to pull them out.

For more organic pest strategies that work hand-in-hand with companion planting, read my roundup of the 10 most effective organic garden pest control methods.

FAQs About Companion Planting

Does companion planting actually work?

The evidence is a mix of solid science and strong anecdote. Marigolds’ effect on nematodes is well-documented. The Three Sisters system is proven over centuries of use. Other combinations like basil near tomatoes improving flavor are harder to prove scientifically but are consistently reported by gardeners. The bottom line: even where the science is limited, companion planting has no downside — at minimum, you’re adding biodiversity to your garden, which is always a good thing.

How many companion plants do I need?

More is generally better, especially for trap crops like nasturtiums. For marigolds and nematode control, a dense planting held for a full season is most effective. For scent-based deterrents like rosemary and sage, even a few plants near susceptible crops can help.

Can I do companion planting in raised beds?

Absolutely. In fact, raised beds are ideal for companion planting because you have total control over what goes where. The same principles apply — just scale down the spacing accordingly.

What’s the best companion plant for tomatoes?

Basil and marigolds are my two must-haves near tomatoes. Basil for hornworm deterrence, marigolds for aphids and whiteflies. Zinnias and parsley are great additions as well.

What should I not plant next to cucumbers?

Keep cucumbers away from sage (said to inhibit their growth) and potatoes (competition for water and nutrients). Cucumbers love radishes, nasturtiums, dill, and marigolds as neighbors.

What should I not plant next to tomatoes?

Fennel is the biggest one — keep it far away from tomatoes. Also avoid planting tomatoes next to brassicas (cabbage, broccoli, kale) or potatoes.

Suggested External Resources

These are current, reputable resources for going deeper on companion planting:

• Rodale Institute Companion Planting Guide — one of the foremost organic farming research organizations; their planting guides are research-backed
• Old Farmer’s Almanac Companion Planting Chart — a comprehensive, regularly updated pairing guide
• Cornell University’s Vegetable Growing Guides — university extension research on integrated pest management including companion planting
• National Gardening Association Plant Guide — great for looking up specific plant combinations and spacing

Companion Planting Is Worth Every Seed

Once you start thinking about your garden as a community of plants working together rather than isolated crops in rows, everything changes. You’ll use fewer pest controls, have more biodiversity, and — honestly — your garden will be much more beautiful.

My biggest suggestion: start with what intimidates you the most. If squash bugs have beaten you every year, surround your squash with nasturtiums and marigolds this season and see what happens. If cucumber beetles are your nemesis, try the radish trick. Small experiments lead to big results over time.

If you haven’t already, also take a look at my spring garden planning checklist — it walks through how I map out a 2,400-square-foot garden and is a great companion (pun intended) to this guide.

Happy planting! 🌿

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