Companion planting is the practice of growing certain plants near each other for mutual benefit. Some combinations repel pests, improve flavor, share nutrients, or provide physical support. Others compete for resources or attract the wrong insects. Knowing the difference can transform your garden.

The Classic Companions

These pairings have been used by gardeners for generations — and modern science backs them up:

  • Tomatoes + Basil — Basil repels aphids, whiteflies, and tomato hornworms. Some gardeners swear it improves tomato flavor, too.
  • Carrots + Onions — Onions mask the scent of carrots from carrot flies, while carrots repel onion flies. A perfect symbiosis.
  • Corn + Beans + Squash — The legendary "Three Sisters" of Indigenous agriculture. Corn provides a trellis for beans, beans fix nitrogen for corn, and squash shades the soil to retain moisture.
  • Lettuce + Tall Plants — Lettuce benefits from partial shade in hot weather. Plant it beneath tomatoes, corn, or trellised beans.

Herbs as Garden Guardians

Herbs are some of the best companions in the garden:

  • Dill attracts beneficial insects like ladybugs and lacewings
  • Rosemary repels cabbage moths and bean beetles
  • Chives deter aphids and Japanese beetles near roses and tomatoes
  • Marigolds (technically a flower) release compounds that suppress root-knot nematodes

Combinations to Avoid

Not all pairings are friendly. Keep these apart:

  • Tomatoes + Fennel — Fennel inhibits tomato growth through allelopathy
  • Beans + Onions/Garlic — Alliums stunt bean growth
  • Peppers + Fennel — Same issue as tomatoes
  • Cucumbers + Aromatic Herbs — Strong herbs like sage can inhibit cucumber growth
A University of California study found that interplanting basil with tomatoes reduced aphid populations by up to 60% compared to tomato monocultures.

Planning Your Companion Layout

The key is thinking in terms of neighborhoods, not individual plants. Group compatible crops together and create buffers between incompatible ones.

Our Smart Planting Planner automatically suggests companion plants for every crop in your results — so you can plan smarter layouts without memorizing charts.

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