Best Companion Plants for Tomatoes (What to Grow Nearby)
Tomatoes are the backbone of most home gardens, and figuring out what to grow around them can make a real difference in your harvest. Some plants genuinely help tomatoes by repelling pests or improving soil. Others compete for the same resources or share the same diseases. And some popular "companion planting" claims are mostly folklore.
I've been growing tomatoes alongside dozens of other plants for years, and I'll tell you what actually works based on my experience and the available research.
Tomato companion planting chart
| Companion Plant | Benefit | How to Plant | Evidence Level |
|---|---|---|---|
| Basil | May repel hornworm moths, aphids; improves flavor (anecdotal) | Interplant between tomato plants, 12 inches away | Moderate |
| Marigolds (French) | Suppress root-knot nematodes; confuse flying pests | Border around tomato bed | Strong (university research) |
| Carrots | Loosen soil around tomato roots; efficient use of space | Plant between tomato plants | Practical (space efficiency) |
| Parsley | Attracts beneficial insects (hoverflies, parasitic wasps) | Interplant or border | Moderate |
| Lettuce | Living mulch; benefits from tomato shade | Under and between tomato plants | Practical (space efficiency) |
| Borage | Attracts pollinators; may deter hornworms | One plant per 4-5 tomato plants | Moderate |
| Garlic | May repel spider mites and aphids | Plant around perimeter of bed | Limited |
| Nasturtiums | Trap crop for aphids; edible flowers | Border or nearby bed | Moderate |
| Chives | May deter aphids with scent | Plant at ends of rows | Limited |
| Asparagus | Tomatoes repel asparagus beetle; different seasons | Adjacent beds (permanent vs annual) | Moderate |
The best companions (in order)
1. Basil — the classic pairing
Every gardening source recommends basil with tomatoes, and for once the hype is mostly justified. The aromatic oils in basil may confuse pests that locate tomatoes by smell — particularly the adult moths that lay hornworm eggs. There's also Italian culinary tradition here (tomatoes and basil just belong together), but the pest management angle has some scientific basis.
Plant basil between your tomato plants, about 12 inches from the stem. Both plants like similar conditions: full sun, warm temperatures, consistent moisture. The basil will benefit from the partial afternoon shade that large tomato plants create in mid-summer.
One practical benefit nobody talks about: having basil right next to your tomatoes means you'll harvest them together for cooking. That's actually the biggest win.
2. French marigolds — proven pest control
This is the companion planting claim with the most research behind it. French marigolds (Tagetes patula, not to be confused with calendula) produce alpha-terthienyl and other compounds in their roots that are toxic to root-knot nematodes. Several university studies have confirmed this effect.
The catch: the marigolds need to grow in the soil for a full season to have their nematode-suppressing effect. It's not instant. But if you grow them around your tomato beds year after year, nematode populations decline significantly. In the short term, their strong scent may also confuse whiteflies and other flying pests.
3. Carrots — space efficiency
Carrots and tomatoes make good neighbors because they use space differently. Tomatoes grow tall and wide above ground. Carrots grow deep below ground. You can plant carrots between tomato transplants early in the season and harvest them before the tomatoes completely fill in.
Carrots also have a reputation for loosening soil, which theoretically benefits tomato roots. Whether this is significant in practice is debatable, but there's certainly no harm in the pairing. For more on growing carrots, see our carrot seed planting guide.
4. Lettuce — living mulch
Lettuce under tomato plants is one of my favorite combinations. The tomatoes provide the afternoon shade that prevents lettuce from bolting in warm weather, and the lettuce acts as a living mulch that keeps the soil cool and moist. It's a genuine win-win.
Plant lettuce transplants between tomato plants about 2-3 weeks after transplanting your tomatoes. Harvest the lettuce as needed — it'll be some of the best lettuce you've grown because it doesn't get stressed by heat. Check our lettuce planting guide for more details.
What NOT to plant near tomatoes
| Avoid This | Why |
|---|---|
| Fennel | Releases compounds that inhibit growth of most nearby plants, including tomatoes |
| Brassicas (cabbage, broccoli, kale) | Heavy feeders that compete for nutrients; may be allelopathic to tomatoes |
| Corn | Shares the same pest (tomato fruitworm = corn earworm); attracts problems |
| Potatoes | Same family (Solanaceae); shares late blight, early blight, and Colorado potato beetle |
| Walnuts (nearby trees) | Produce juglone, which is toxic to tomatoes and causes wilt |
| Dill (mature) | Young dill is fine, but mature dill may inhibit tomato growth |
The potato-tomato warning is the most important one here. If late blight hits your potatoes, it will jump to your tomatoes in days. Keep them as far apart as your garden allows — different beds, different sides of the yard if possible.
Layout ideas
Here's how I typically arrange my tomato bed in a 4x8 foot raised bed:
- 3 tomato plants spaced 24 inches apart along the back (north side)
- Basil planted between and in front of each tomato
- Lettuce as ground cover in the front row
- Marigolds at each corner and along the front edge
- One borage plant at one end for pollinators
This layout maximizes space, provides pest management, and gives you three crops (tomatoes, basil, lettuce) from one bed. For more layout ideas, check our garden planning guide.
If you're figuring out when to get your tomatoes started for the season, our planting calendar gives you customized dates based on your zip code. Also see our detailed guides on when to plant tomatoes by zone and how deep to plant tomato seeds.
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Frequently asked questions
What should you not plant next to tomatoes?
Avoid planting fennel, brassicas (cabbage, broccoli, cauliflower), corn, and other nightshades like potatoes near tomatoes. Fennel inhibits tomato growth, brassicas compete for nutrients, and potatoes share diseases like late blight.
Is basil a good companion plant for tomatoes?
Yes, basil is probably the best companion plant for tomatoes. It may repel certain pests like hornworm moths and aphids, and many gardeners report better-tasting tomatoes when basil grows nearby.
Can you plant peppers next to tomatoes?
You can, but it's not ideal. They're both nightshades, so they share pests and diseases. If one gets early blight or hornworms, the other will too. If you plant them together, watch carefully for signs of disease.
Do marigolds really help tomatoes?
French marigolds (Tagetes patula) do have proven benefits — they suppress root-knot nematodes in the soil and their strong scent may confuse some flying pests. Plant them around the perimeter of your tomato bed.