Companion Planting: 12 Pairings That Actually Work

Companion planting is one of those gardening topics where 80% of the advice is repeated from a 1970s book that was itself repeating folklore. The other 20% genuinely works — and works well.

Here are the pairings we recommend most often through the GrowLog AI chat, with a short reason each one earns its place.

Why pair plants at all?

Plants don't grow in isolation in nature, and they don't have to in your garden either. Good pairings give you:

• Pest disruption — strong-scented or visually different plants confuse pests that hunt by smell or sight.
• Pollinator attraction — flowering companions bring bees and predatory insects to plants that need them.
• Vertical layering — tall plants share light with short, deep-rooted plants share soil with shallow-rooted.
• Nitrogen sharing — legumes feed the soil for nearby hungry crops.

The 12 pairings we trust

1. Tomatoes + basil

The classic that's actually true. Basil's volatile oils confuse the tomato hornworm moth. They also want the same water and sun.

2. Tomatoes + marigolds

French marigolds release alpha-terthienyl from their roots, which suppresses nematodes for years. Plant generously.

3. Carrots + onions

The onion's scent masks the carrot for carrot fly. The carrot returns the favor for onion fly. Plant in alternating rows.

4. Corn + beans + squash (the Three Sisters)

Beans fix nitrogen for the corn, corn provides a trellis for the beans, squash shades the soil and deters raccoons. The original polyculture.

5. Cabbage + dill

Dill attracts the parasitic wasps that prey on cabbage worms. Bonus: you get pickling dill.

6. Lettuce + radishes

Radishes mature fast and loosen the soil. By the time the lettuce is sizing up, the radishes are out — no competition.

7. Cucumbers + nasturtiums

Nasturtiums act as a trap crop for aphids and cucumber beetles. Sacrifice them so your cukes don't get hit.

8. Peppers + oregano

Oregano flowers attract hoverflies, which eat aphids. Keep it trimmed so it doesn't take over.

9. Beans + summer savory

Folk wisdom says it improves the flavor. What's documented: it repels bean beetles.

10. Brassicas + nasturtiums

A second use for nasturtiums — they pull cabbage moths away from broccoli, kale, and cabbage.

11. Strawberries + borage

Borage attracts pollinators and is said to improve strawberry flavor and yield. Bees love it.

12. Squash + radishes

Plant radishes at the base of squash hills. They deter squash vine borers and are harvested before the squash needs the space.

Pairings to avoid

Some plants actively compete or attract each other's pests:

• Tomatoes + brassicas — they compete heavily for the same nutrients.
• Onions + beans / peas — onions inhibit legume growth.
• Fennel + almost anything — fennel suppresses neighboring plants. Give it its own bed.
• Potatoes + tomatoes — both nightshades, both susceptible to the same blights. One infection takes out both.

How to test pairings in your own garden

This is where a garden journal earns its keep. Plant the same crop in two configurations — one with the companion, one without — and log:

• Pest pressure (how many you see per week)
• Yield
• Time to harvest
• Plant size

After one or two seasons you'll know what works in your garden, not someone else's. That's the data GrowLog AI captures automatically when you describe your beds — so by year three, the AI knows your specific pairings and can recommend new ones to try.

Companion planting isn't magic. It's just paying attention, repeatably, over years. That's something any gardener can do.