The main vegetables not to plant together include fennel near most crops and onions beside your beans or peas. These pairings fail because plants compete for food and water. Some even wage chemical war through their roots against their neighbors.
I found out about bad vegetable combinations during my third year of growing food. My bean plants stayed small all summer because I put them next to onions. Those onions sent sulfur into the soil that stopped my beans from making their own nitrogen. You can avoid this same mistake by keeping these two crops far apart in your garden beds.
Some plants send out harmful chemicals from their roots that stop seeds from sprouting nearby. Fennel does this worse than any other garden plant. It hurts tomatoes, beans, and peppers that grow within several feet of it. You should give fennel its own spot away from your main beds or grow it in a pot by itself.
Plants that fight each other also grab the same nutrients from the soil. When you put two hungry feeders like corn and tomatoes together, they battle over nitrogen. One or both crops will look weak and yellow even if you feed them well. You get better results by spacing out your heavy feeders across different parts of your garden.
Fennel
- Problem crops: Your tomatoes, peppers, and beans will grow poorly when planted within 3 feet of fennel.
- Root chemicals: Fennel sends out compounds that slow root growth and stop seeds from sprouting nearby.
- Your solution: Grow fennel in pots or put it at least 10 feet away from your main vegetable beds.
Onion Family
- Problem crops: Your beans and peas won't fix nitrogen well when onions, garlic, or leeks grow near them.
- Chemical effect: Sulfur from alliums hurts the good bacteria that your legumes need to make nitrogen.
- Your solution: Keep your legumes and onion family plants in beds at least 4 feet apart.
Brassicas
- Problem crops: Your cabbage, broccoli, and kale share pests that move fast between close plantings.
- Shared pests: Clubroot spreads through soil fast when you grow several brassicas in the same spot.
- Your solution: Move your brassica crops each year and keep them 6 feet from strawberry beds.
Your nightshade crops need space from each other too. Tomatoes, peppers, eggplants, and potatoes all draw the same bugs. Colorado potato beetles will feast on them all if you plant them in one area. Late blight can jump from your potatoes to your tomatoes in days when they sit close together.
Keep at least three feet between plants that don't get along. For fennel, push that gap to ten feet or more. You can also use raised beds or containers as barriers between problem pairs. Plan your layout on paper before spring so you know where each crop will go.
Write down which plants did poorly each year in your garden journal. Check if a bad neighbor caused the trouble. Moving one crop to a new spot often fixes growth problems that extra water and food couldn't solve. You might find that your struggling plants just needed better company all along.
Read the full article: 10 Best Vegetable Garden Layout Ideas
