Companion Planting Checker
Find out which plants grow best together in your garden. Select any two plants to check their compatibility, get growing tips and see a full companion matrix.
How Companion Planting Works
Companion planting is the practice of growing certain plants near each other for mutual benefit. Some plants repel pests that attack their neighbors, while others attract pollinators or fix nitrogen in the soil. The most famous example is the Three Sisters method used by Indigenous Americans — corn, beans and squash planted together where corn provides a trellis for beans, beans fix nitrogen for all three, and squash shades the soil to retain moisture and suppress weeds. This tool checks compatibility for 30 common garden plants and explains why each pairing works or does not.
Best Companion Planting Combinations
Tomato and basil is the classic companion pair — basil repels aphids and whiteflies while improving tomato flavor. Carrots and onions protect each other because carrot flies dislike onion scent and onion flies avoid carrot foliage. Marigolds are the universal companion because they repel nematodes, aphids and whiteflies from nearly any vegetable. Planting herbs like rosemary, sage and thyme near brassicas deters cabbage moths. Nasturtiums serve as trap crops, luring aphids away from your vegetables.
Plants That Should Never Be Planted Together
Fennel is the most notorious bad companion — it releases substances that inhibit growth in most nearby plants and should be planted in isolation. Tomatoes and potatoes share the same diseases (blight) and attract the same pests, so keeping them apart reduces infection risk. Beans and onion family plants (garlic, onions, shallots) are poor neighbors because alliums stunt bean growth. Dill initially helps carrots but once it flowers, it can cross-pollinate and reduce carrot seed quality. Always check compatibility before planting to avoid stunted growth, pest problems or reduced yields.
Tips for Planning Your Companion Garden
Start with your main crop and build companions around it. If tomatoes are your priority, surround them with basil, carrots and marigolds. Use the quick-reference matrix in this tool to see all companions for any plant at a glance. Rotate your companion groups each year to prevent soil depletion. Interplant flowers like marigolds and nasturtiums throughout your vegetable beds — they attract beneficial insects and add color. Keep a garden journal to track which companion combinations perform best in your specific climate and soil conditions.
Frequently Asked Questions
What is companion planting?
Companion planting is growing certain plants near each other for mutual benefit. Good companions may repel pests, attract pollinators, fix nitrogen in the soil or provide physical support like shade or a trellis. Bad companions compete for nutrients, attract the same pests or release chemicals that inhibit each other's growth.
What are the Three Sisters in companion planting?
The Three Sisters are corn, beans and squash — a Native American planting method. Corn provides a natural trellis for beans to climb, beans fix nitrogen in the soil to feed all three plants, and squash spreads along the ground to shade soil, retain moisture and suppress weeds.
Why should tomatoes and potatoes not be planted together?
Tomatoes and potatoes are both nightshades and share the same diseases, especially late blight. Planting them together increases the risk of blight spreading rapidly through both crops. They also compete for the same soil nutrients.
Why is fennel bad for most garden plants?
Fennel releases allelopathic compounds from its roots that inhibit the growth of most nearby plants including tomatoes, beans and brassicas. It is best planted in its own isolated bed or container, away from the main vegetable garden.
How does basil help tomatoes?
Basil repels aphids, whiteflies and mosquitoes that commonly attack tomato plants. Some gardeners also report that basil improves tomato flavor when planted nearby, though this is anecdotal. The strong scent of basil confuses pests looking for tomato plants by smell.
Can I plant onions near beans?
No, onions and other alliums (garlic, shallots, leeks) are poor companions for beans and peas. Alliums release sulfur compounds that can stunt legume growth and interfere with nitrogen-fixing bacteria in bean roots. Keep them in separate beds.