PlantWise

Companion planting chart

Tap a vegetable to light up its friends and foes. Green check: good neighbours. Red cross: keep apart. Every pairing links to the reason, and whether it’s proven or folklore.

Nothing selected. Tap any vegetable above.

The full chart

CropTomatoPepperPotatoPumpkinSquashZucchiniCucumberStrawberryGarlicOnionCarrotLettuceBeanPeaBroccoliSweet corn
Tomato✓✕✕✓✓✓✓✕✕
Pepper✓✕✓✓✕
Potato✕✕✕✕✕✕✓✓
Pumpkin✕✕✕✓✓
Squash✕✕✕✓✓
Zucchini✕✕✓✓
Cucumber✕✕✓✓✓✓
Strawberry✕✓✓✓✕
Garlic✓✓✓✕✕
Onion✓✓✓✓✓✕✕✓
Carrot✓✓✓✓✓✓✓
Lettuce✓✓✓✓✓✓✓
Bean✕✓✓✓✓✓✕✕✓✓
Pea✓✓✕✕✓✓
Broccoli✕✕✓✓
Sweet corn✕✓✓✓✓✓

What the evidence says

Companion planting mixes solid horticulture with a lot of garden lore. Reviews by extension services, including Washington State University’s Linda Chalker-Scott, find that the reliable benefits come from a few mechanisms:

  • Shared pests and diseases. Keeping tomatoes and potatoes apart, or rotating squash family crops, cuts disease pressure. This is the best-supported “bad companion” advice.
  • Habitat for predators. Flowering herbs such as dill, alyssum and borage feed hoverflies and parasitic wasps that eat aphids and caterpillars.
  • Physical help. Corn holds up beans; squash leaves shade out weeds; tall crops shade lettuce in summer.
  • Trap crops. Nasturtiums draw aphids away from nearby crops, when you then remove the infested plants.

Claims that one vegetable “improves the flavour” of another, or that onions “stunt” beans, are traditional and largely untested. They do little harm, but don’t rearrange a garden around them.

Questions gardeners ask

Does companion planting actually work?

Some of it. Well-supported effects include trap crops, flowers that feed predatory insects and pollinators, French marigolds suppressing root-knot nematodes when grown densely, and keeping crops that share diseases apart. Many traditional pairings have never been tested, so this chart labels each reason as research, practical or tradition.

What should not be planted next to tomatoes?

Keep tomatoes away from potatoes (shared blight), black walnut (juglone toxicity) and sweet corn (corn earworm is also tomato fruitworm). Fennel is traditionally grown apart from most vegetables.

What are the Three Sisters?

A planting system developed by Indigenous peoples of North America: corn provides a pole for climbing beans, and squash shades the soil to hold moisture and suppress weeds.

How far apart do “bad” companions need to be?

For shared diseases, different beds and a rotation of three to four years matter more than a few feet. For competition and shading, simply giving each plant its own space is usually enough.