Companion Planting Chart: What Grows Well Together

This companion planting chart lists only pairings that a university extension program, a national horticulture society or a published study supports. Each entry says how strong that support is: measured in trials, recommended by extension programs, or traditional garden practice.

The chart

Each crop's own page explains every pairing in the chart and lists its sources.

Check the shared growing needs first

1. Do both crops suit the same sunlight?
2. Can they use a similar watering pattern?
3. Will their mature leaves and roots have enough room?
4. Will the taller crop shade the shorter crop at the wrong time?
5. Can you still reach both crops to water and harvest?

Use space and timing on purpose

A taller crop and a lower crop may use different layers of the same bed. A quick crop may be harvested before a slower crop fills the space. These are useful layout choices, but both plants still need their saved spacing.

Popular claims the evidence does not support

• Marigolds keep Colorado potato beetles off potatoes. University of Minnesota Extension says multiple studies have shown this to be untrue.
• Mint and other strong-smelling herbs repel pests. Washington State University Extension says field research has not shown this for mint or any other aromatic herb.
• Marigolds protect the whole garden. UMass Extension says marigold roots harm root nematodes only after marigolds are grown as a cover crop and dug into the soil, and that very little other evidence supports their reputation.
• Marigolds planted after whiteflies show up will fix the problem. In a 2019 greenhouse study, late marigolds helped very little. They worked when they grew beside the tomatoes from the start.
• Corn, beans and squash grown as the three sisters give bigger harvests. Washington State University Extension found no compelling published evidence that it helps yields or soil.

Washington State University horticulturist Linda Chalker-Scott, quoted by University of Arizona Extension, puts it plainly: traditional companion planting charts have entertainment, not scientific, value. That is why this chart leaves out any pairing without a source.

Do not rely on a companion plant to control a serious pest or disease. Identify the exact problem and use advice written for that crop and pest.

Try a pairing as a small test

Keep a simple note of the crop varieties, spacing, dates, and result. A pairing that seems helpful in one garden may behave differently with another climate, pest, soil, or planting time.

Sources

• Companion planting in home gardens (University of Minnesota Extension)
• Three ways to use companion planting (Royal Horticultural Society)
• GYO did you know? The three sisters (Royal Horticultural Society)
• Gardening with Companion Plants (Home Garden Series), EM128E (Washington State University Extension)
• Companion planting in the vegetable garden (UMass Amherst Center for Agriculture, Food, and the Environment)
• Companion Planting (Backyard Gardener #254) (University of Arizona Cooperative Extension)
• Companion planting with French marigolds protects tomato plants from glasshouse whiteflies through the emission of airborne limonene (PLOS ONE (Newcastle University study))
• Perimeter Trap Cropping Works! (UConn Extension Integrated Pest Management)
• Perimeter trap crop approach to pest management on vegetable farms (Northeast SARE (University of Massachusetts project))
• Benefits of pollinator-attracting companion plants (Texas A&M AgriLife)
• Effects of Plant Density and Diversity on the Population Dynamics of a Specialist Herbivore, the Striped Cucumber Beetle, Acalymma vittata (Fab) (Ecology (Catherine E. Bach study))
• Companion planting to attract pollinators increases the yield and quality of strawberry fruit in gardens and allotments (Ecological Entomology (University of Sussex study))
• Tomato: Late blight (Washington State University Extension)
• Black Walnut Toxicity to Plants (University of Wisconsin-Madison Extension)
• Tomato Fruitworm (Utah Vegetable Production and Pest Management Guide) (Utah State University Extension)
• Strawberry Disease - Verticillium Wilt (Penn State Extension)
• Growing Raspberries in Your Home Garden (Oregon State University Extension Service)
• Growing raspberries in the home garden (University of Minnesota Extension)
• Planting and Growing a Home Garden (Penn State Extension)
• Growing Together: The Three Sisters Garden (Penn State Extension)
• Raised Beds (Clemson Cooperative Extension)