What Is Companion Planting?
Companion planting is the practice of growing certain plants near each other for mutual benefit. Benefits include pest deterrence, pollinator attraction, soil improvement, space efficiency, and even improved flavor.
The Science Behind It
Some companion planting is well-supported by research. Marigolds release alpha-terthienyl from their roots, which kills root-knot nematodes in the soil. Beans and peas fix atmospheric nitrogen into plant-available forms, genuinely feeding neighboring plants. Aromatic herbs like basil produce volatile compounds that can confuse pest insects looking for their target crop by scent.
Other companion planting wisdom is more anecdotal, passed down through generations of gardeners. Even when the mechanism is unclear, the practical advice often works because it promotes biodiversity, which is universally beneficial in a garden ecosystem.
Look up companions for any specific crop.
Open Companion Planting Guide →The Three Sisters
The most famous companion planting system: corn, beans, and squash. Corn provides a structure for beans to climb. Beans fix nitrogen that feeds the corn. Squash spreads across the ground, shading the soil to retain moisture and suppress weeds. This system was developed by Indigenous peoples of North America and is still one of the most efficient ways to grow these three crops together.
General Rules
- Grow aromatic herbs (basil, rosemary, thyme) near vegetables to confuse pests
- Plant marigolds and nasturtiums throughout the garden as pest traps and repellents
- Keep alliums (onions, garlic) away from beans and peas
- Rotate plant families each year to prevent disease buildup
- Avoid planting the same family in the same spot two years running
The best companion planting strategy is simple: grow a diverse garden. Monocultures attract pests. Mixed plantings confuse them.