Spring gardening season is exciting—but planting the wrong neighbors can spell disaster for your blooms and harvests. Some plants just don’t get along, competing for nutrients, stunting each other’s growth, or attracting pests that destroy the peace. Knowing which plant combinations to avoid can mean the difference between a thriving garden and a sad, stunted mess. This guide uncovers the worst offenders when it comes to companion planting. Avoiding these plant combos will help your garden grow healthier and stronger this spring.
1. Tomatoes and Corn
Tomatoes and corn may look like they’d grow well side-by-side, but they attract the same pests—especially the corn earworm and tomato fruitworm. This makes it easy for infestations to spread quickly. Both are also heavy feeders, competing for nitrogen and other nutrients in the soil. Neither gets what it needs to thrive when they're grown too close. This combo can result in weaker plants and smaller yields. To avoid this, plant tomatoes away from any tall crops like corn.
2. Beans and Onions
Beans and onions are a classic example of bad companions. Onions release substances into the soil that can inhibit bean growth. On the other hand, beans try to enrich the soil with nitrogen, which onions don’t need much of. This causes a mismatch in soil chemistry that leads to poor yields. Keep all alliums—like garlic, leeks, and shallots—away from your legumes. Give them their own space to thrive.
3. Carrots and Dill
While they might look cute together in a garden row, carrots and dill can cause trouble. Dill stunts carrot growth by releasing compounds that affect root development. The plants are also closely related, which can lead to cross-pollination and weakened varieties. Plus, dill attracts pests like aphids that can harm tender carrot tops. It’s better to keep dill far from root veggies. Choose companion herbs like chives or rosemary instead.
4. Cucumbers and Sage
Cucumbers and sage don’t mix well. Sage has strong aromatic oils that can interfere with cucumber growth. The herb also repels some insects that cucumbers rely on for pollination. This combo may lead to stunted vines and fewer fruits. Instead of sage, pairing cucumbers with nasturtiums or marigolds offers better pest protection. Keep the strong herbs at a distance.
5. Potatoes and Tomatoes
Both potatoes and tomatoes belong to the nightshade family, which makes them especially vulnerable to similar diseases—especially blight. If one gets infected, it’ll likely spread quickly to the other. They also compete heavily for nutrients and space underground. Planting them together can stunt growth and lead to poor yields. Keep them far apart for healthier roots and fruit. Rotate these crops each year to prevent disease buildup.
6. Peppers and Fennel
Fennel is a known bad neighbor in the garden, and peppers are one of its worst victims. Fennel releases allelopathic chemicals that inhibit growth in many plants. This includes stunting the height and yield of peppers. It also competes for space and root resources. For the best results, grow fennel in its own bed, away from your veggies. Companion herbs like basil are much better for peppers.
7. Lettuce and Broccoli
These leafy greens might seem compatible, but they’re actually bad neighbors. Broccoli is a heavy feeder and can quickly drain the soil of nutrients that lettuce needs. It also creates too much shade, which stresses sun-loving lettuce. The result is bitter, leggy lettuce heads and weak broccoli stalks. Give each plant plenty of space and separate beds. Consider companion planting lettuce with carrots or radishes instead.
8. Garlic and Beans
Garlic produces compounds that can suppress fungal growth and inhibit beans' root development. This makes it hard for beans to fix nitrogen in the soil, hurting their growth. When planted together, both can suffer stunted growth and low productivity. Keep garlic with crops like beets or cabbage that benefit from its pest-fighting qualities. Let beans thrive with corn or squash instead.
9. Melons and Potatoes
These two compete fiercely for nutrients and space, especially underground. Potatoes can also harbor diseases that melons are susceptible to, leading to cross-contamination. Melons need lots of room and sunlight, while potatoes tend to crowd them out. This bad match often results in smaller fruits and weak vines. Grow melons in open, sunny areas and leave potatoes in a separate bed. Crop rotation helps protect both plants.
10. Sunflowers and Potatoes
Sunflowers might be great for pollinators, but they release allelopathic toxins into the soil. These chemicals can harm potatoes, stunting their growth and yield. Both also compete for deep soil nutrients and water. If planted too close, the result is underdeveloped tubers. Use sunflowers on garden borders instead of near root crops. Give potatoes room to expand underground.
11. Spinach and Strawberries
Though both love cool weather, spinach, and strawberries make bad neighbors. Strawberries can spread aggressively, stealing space and nutrients from spinach. Their dense leaves also create shade, slowing spinach growth. Plus, they can attract the same fungal diseases. Plant strawberries with borage or thyme instead. This will give spinach a clearer path to sun and airflow.
12. Kale and Grapes
Grapevines can cast heavy shade and reduce airflow, which kale doesn’t tolerate well. Kale also attracts pests like cabbage worms, which can spread to grapes. Meanwhile, grape roots can outcompete kale for water and nutrients. This pairing usually results in limp leaves and unhappy vines. Grow kale in sunnier areas with companions like beets or celery. Keep the grapes on trellises on the other side of the garden.
13. Radishes and Hyssop
Hyssop’s strong scent and chemicals can interfere with radish germination. Radishes need loose, open soil, while hyssop grows dense and bushy. Together, they compete for space and can stunt each other’s development. Hyssop may also attract pollinators away from radish flowers. If you love herbs, plant hyssop with cabbage instead. Radishes do better with lettuce and peas.
14. Cabbage and Strawberries
Strawberries attract slugs and beetles that love to nibble on cabbage leaves. Their runners can also invade cabbage space and steal nutrients, leading to slower growth and more pest damage. Cabbage thrives better with aromatic herbs like dill and sage. To avoid these issues, keep strawberries away from all brassicas.
15. Eggplant and Fennel
Like peppers, eggplants hate fennel. Fennel’s allelopathic effects suppress eggplant growth and flowering. They also compete below ground, weakening both plants. This pairing often results in leggy eggplants with poor fruit development. Stick with basil or thyme as companions for eggplant. Keep fennel far from your veggie beds.
16. Beets and Pole Beans
Pole beans can interfere with beetroot development by taking too much nitrogen from the soil. Beets prefer low-nitrogen environments for better bulb formation. Beans also shade out smaller beet seedlings. Together, this leads to uneven crops. Grow beets with leafy greens instead. Let beans climb with companions like corn.
17. Celery and Carrots
These root crops need similar nutrients and soil space, making them direct competitors. Carrots also suffer when taller celery shades them out. This leads to smaller, less flavorful roots for both. Pests like carrot flies and aphids may also multiply when these two are together. Separate them to give each the best chance at growth. Pair celery with onions and carrots with tomatoes instead.
18. Zucchini and Potatoes
These two are space hogs—zucchini spreads out, while potatoes need underground room. Crowding them together leads to tangled roots and smaller harvests. Potatoes may also pass on fungal diseases to zucchini vines. It’s better to give zucchini its own sunny patch and leave potatoes to grow in deeper, separate beds.
19. Broccoli and Peppers
Broccoli’s nutrient needs are high, and peppers struggle to compete. They also require different soil pH levels to thrive. This combo often results in smaller pepper fruits and underdeveloped broccoli heads. Keep these apart to ensure better yields for both. Peppers love basil and carrots nearby instead.
20. Turnips and Mustard Greens
Mustard greens attract pests like flea beetles, which devastate turnip leaves and roots. They also compete for nutrients and water, stressing both crops. Turnips do better with legumes or herbs like mint. Avoid planting mustard greens near other brassicas, too. Give each crop its own bed for best results.
21. Peas and Garlic
Garlic’s natural chemicals may help fight disease, but they’re bad for peas. Peas rely on root bacteria to fix nitrogen, which garlic disrupts. This weakens growth and yields in peas. They’re better off with carrots, corn, or radishes as neighbors. Keep garlic paired with plants that don’t need nitrogen-rich soil.
Choose Wisely for a Thriving Spring Garden
The wrong plant combos can ruin even the best-laid garden plans. From chemical warfare underground to shared pests above, these pairs show just how tricky companion planting can be. Keep a smart layout, give plants space, and always double-check which neighbors get along. Give your plants the best chance by choosing companions wisely!