Companion Planting Checker
Find out which plants grow well together and which to keep apart. Look up companions for any plant, or check if a specific pair is compatible.
Basil repels aphids and improves flavor
✅ Good Companions
❌ Keep Away
Why it matters
🍅Tomato: Basil repels aphids and improves flavor
Companion planting uses natural relationships between plants. Good companions may repel pests, attract pollinators, fix nitrogen, provide shade, or improve flavor. Foes may compete for nutrients, attract the same pests, or release growth-inhibiting chemicals.
Common questions
Yes, companion planting is backed by both traditional gardening wisdom and scientific research. Marigolds have been proven to repel nematodes, basil can reduce aphid populations near tomatoes, and legumes genuinely fix nitrogen in soil that benefits neighboring plants. While not every folk pairing has strong evidence, the core principles of pest confusion, nutrient sharing, and beneficial insect attraction are well documented.
How Companion Planting Works
Companion planting relationships are drawn from agricultural extension research, traditional farming practices, and documented scientific studies on allelopathy (chemical interactions between plants). Plants benefit each other through several mechanisms: nitrogen fixation (beans and peas feed neighboring plants), pest confusion (strong-scented herbs mask crop scents from pests), trap cropping (nasturtiums lure aphids away from vegetables), and pollinator attraction (flowers near crops improve fruit set). Antagonistic relationships typically involve chemical compounds. For example, black walnut trees release juglone, which inhibits tomato and pepper growth.
Putting Companions Into Practice
- The Three Sisters (corn, beans, squash) is the most well-documented companion planting system. Corn provides a trellis for beans, beans fix nitrogen for all three, and squash leaves shade the soil to retain moisture.
- Plant basil within 18 inches of tomatoes. Research from Purdue University shows basil repels thrips and may improve tomato flavor.
- Border your garden with marigolds. Their roots release thiopene, a compound that suppresses harmful root-knot nematodes in the surrounding soil for up to a year.
- Use the spacing calculator to plan how many companions fit alongside your main crops, and check the watering calculator to balance water needs when pairing plants with different requirements.
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Quick answer▾
Companion planting pairs vegetables, herbs, and flowers that benefit each other through pest repulsion, pollinator attraction, or nutrient sharing. Classic examples include tomatoes with basil, corn with beans and squash (the Three Sisters), and marigolds near most vegetables to repel harmful nematodes.
Data last updated: March 2026