Do you know which plants you should never grow together?

As much as you might love to have a garden full of your favorite plants, not all of them make good neighbors. Companion planting is a simple and natural way to control pests while helping flowers, herbs, and veggies thrive—but some plants just don’t make good neighbors.

They can compete for light, nutrients, and space, which can stunt their growth. Not only that, but they might attract unwanted pests, spread disease, and even harm each other’s development. These plant pairings are definitely a recipe for garden disaster!

You surely want to create and maintain a thriving and harmonious garden, and I’m here to help! Without further ado, here are the plants you should never grow together:

1. Brassicas with strawberries

Brassicas, including cabbage, Brussels sprouts, and broccoli, are typically targeted by cabbage loopers, which can cause annoying holes in the plants’ leaves. Sadly, these troublesome insects aren’t picky eaters and won’t say no to nearby veggies and fruits.

The reason why you should never plant these two together is that your delicious strawberries are more likely to develop cabbage looper infestations, and that’s never pleasant. So, if you want to grow fresh and sweet fruits, avoid growing them next to your brassica veggies.

However, you can still achieve the garden of your dreams, so here’s what you can do instead. Pair your brassicas with onions or garlic. Pests don’t like these strong smells, so they’ll be gone sooner than you think.

Another good combination for brassica is with peas and beans, which put nitrogen back into the soil. If you want your strawberries to thrive, grow them with rhubarb, spinach, and lettuce.

2. Asparagus with alliums

Another pair of plants you should never grow together? Asparagus and alliums. While garlic, onions, and other allium plants have a strong, pest-repelling scent, they’re bad news for asparagus. Instead of helping, they stunt its growth and compete for nutrients. So, if you want thriving asparagus, keep those pungent alliums at a distance!

Other than that, harvesting alliums can disrupt your asparagus, making it less likely to grow. Sounds like the perfect recipe for trouble, doesn’t it? If you want to help your asparagus thrive, plant it with parsley, basil, or nightshades such as eggplant and tomatoes.

As for alliums, they get along with brassicas, tomatoes, and beets, so keep these in mind when planting your veggies.

3. Dill with carrots

Since they’re part of the same Umbellifer family, carrots and dill might seem like an ideal garden duo, but planting them together is a big mistake! These two can cross-pollinate, leading to poor-quality hybrid seeds—not exactly what you’d like in your garden. Not to mention, dill attracts carrot flies, which chew holes in your delicious carrots.

While these two are plants you should never grow together, I know exactly what you can plant instead. Dill thrives with cucumbers, lettuce, and brassicas, helping to keep pests at bay.

If you want to protect your carrots, plant them with sage or radishes. This combination will ensure your veggies are thriving, fresh, and tasty!

4. Potatoes with tomatoes

Another pair of plants you should never grow together is tomatoes and potatoes. They might seem like a natural pair, but it’s actually a gardening disaster in disguise. They both belong to the nightshade family, which means they attract the same ruthless pests—think of Colorado potato beetles and tomato hornworms. Yikes, definitely not pleasant!

Growing them side by side creates a paradise where pests can thrive, making it easy for invaders to spread fast and eat away at your beautiful garden. And that’s not all! These leaf-stripping pests can overwinter in the soil, returning to create chaos year after year!

Potatoes are heavy feeders and can immediately drain nitrogen from the soil. However, to keep your garden healthy and thriving, you can pair them with peas or beans, which restore nitrogen.

5. Cucumber with sage

Continuing with these plants you should never grow together, it’s now time to talk about cucumbers and sage. These two might be garden favorites, but they’re not friendly neighbors! Professional gardeners say that sage can interfere with cucumber growth, leading to smaller harvests.

Other than that, the watering needs don’t match up. Either the cucumbers don’t get enough water, or the sage gets too much of it. So, what exactly would be the result? A struggling garden.

But don’t worry, though; I have some alternatives for you. Oregano and dill are wonderful companions for cucumbers; they keep pests away and still allow your tasty veggies to flourish.

If you want to maximize space, you can plant cucumbers with beets or carrots, as they allow each other room to breathe and grow. Sage, on the other hand, is great with tomatoes and brassicas, keeping pests away.

6. Legumes with alliums

Garlic, onions, and other alliums, such as chives, shallots, scallions, and leeks, might be garden superstars, but they’re not good neighbors to beans and peas. These are plants you should never grow together because alliums interfere with legume growth and reduce harvests.

What’s worse is that their natural antibacterial properties can impact the bacteria responsible for fixing nitrogen, making it harder for your precious legumes to enrich the soil.

If you want to take your gardening game to the next level, you should know that peas and beans get along with eggplants, cucumbers, and radishes. You can also add marigolds for an extra pest-protection layer. This fantastic combination will keep common garden invaders at bay while also adding a stunning pop of color to your natural oasis!

7. Turnips with other root veggies

Turnips, potatoes, and radishes might seem like great garden buddies, but planting them together can lead to a bit of a competition! Since they all grow down into the soil, they end up fighting for space, water, and nutrients. Not exactly the perfect recipe for a thriving garden! Unfortunately, this can cause their growth to stall and result in smaller harvests.

So, what can you do instead? Turnips are fantastic at keeping aphids away, making them perfect companions for cabbage, broccoli, and lettuce. These plants often attract pesky little critters, so the combination mentioned above is nothing but ideal!

8. Corn with tomatoes

Tomatoes and corn make a fabulous salsa or summer salad, but when it comes to growing them together, it’s a recipe for disaster! Both of them are primary targets for corn earworms (aka tomato fruit worms), so planting them together creates a paradise for pests. Other than that, since they’re both heavy feeders, they’re more likely to compete for nutrients. Unfortunately, this will result in smaller harvests and weaker plants.

What you can do instead is to plant corn with peas or beans, as they’ll restore nitrogen to the soil. Corn also pairs well with cucumbers or squash, which provide shade and maximize the space available in your garden.

What are your thoughts on these plants you should never grow together? Have you ever tried any of these combinations? Did you have any problems? I would love to know more about your experience, so leave a comment below, and let’s chat!

If you want to learn more about this topic and how to achieve the garden of your dreams, here’s a wonderful ebook! It will also help you enhance your outdoor space with minimum effort!

If you found this article helpful and would like to check out something else from The American House, here’s another post you won’t want to miss: Alternative Gardening Methods: 12 Genius Ways to Cultivate Without a Backyard