What are Bad Companion Plants for Tomatoes

What are bad companion plants for tomatoes? Let’s find out! If you’re a tomato lover and enjoy growing them in your garden, you might already know that they are one of the most versatile and easy-to-grow vegetables. However, did you know that some plants can hinder your precious tomatoes’ growth? These are known as bad companion plants.

Bad companion plants are those that have a negative impact on the growth and health of other plants around them. 

In this article, we’ll go over some common bad companion plants for tomatoes so that you can avoid planting them together and ensure a bountiful harvest of juicy tomatoes. 

A close-up shot of tomatoes. Background is a blurred shot of other tomato plants.

Common Bad Companion Plants for Tomatoes:


These are vegetables like broccoli, cabbage, cauliflower, kale, kohlrabi, and Brussels sprouts, which are known for their hardiness and ability to survive in cooler temperatures. While they might seem like a good match for tomatoes – which also thrive in cool climates – the truth is that these two plants have different needs regarding soil nutrients. Take note that tomatoes require a lot of nitrogen to produce healthy fruit.


Firstly, corn and tomatoes have different soil requirements. Tomatoes prefer well-drained soil that’s rich in organic matter, while corn prefers heavier soils that retain moisture better. When planted together, one crop will likely suffer from being in the wrong type of soil.

Secondly, both crops attract different pests and diseases, which can spread between them easily when planted together. For example, tomato fruit worms are attracted to both plants, which means they’ll quickly move from the tomatoes to the corn and vice versa.

Lastly, planting these two crops together can lead to competition for resources such as water and nutrients.


Fennel produces chemicals that can stunt the growth of tomato plants. This means that if you plant tomatoes next to fennel, they may not grow as tall or produce as much fruit as they would otherwise.

Additionally, tomato plants and fennel have similar nutrient requirements, so planting them together may lead to competition for resources like water and nutrients.

Planting tomatoes with fennel can also attract pests like aphids and whiteflies. These insects are attracted to the sweet scent of fennel and can quickly infest nearby tomato plants.


Dill is known to attract tomato hornworms, which are destructive pests that can quickly destroy a tomato plant. These worms are attracted to the scent of dill and will lay their eggs on nearby tomato leaves. Once hatched, the larvae will then proceed to eat through the leaves of the tomato plant and strip it bare.

Another reason not to plant tomatoes with dill is that they both require very different growing conditions. Tomatoes need full sun and well-draining soil, while dill thrives in partial shade and moist soil.


Firstly, tomatoes and potatoes require different soil conditions to thrive. Tomatoes prefer well-draining soil that is rich in organic matter, while potatoes need loose and fertile soil with plenty of moisture. Planting them together can result in uneven growth patterns and stunted development.

Secondly, planting these two crops together can increase the risk of diseases spreading between them. Both tomatoes and potatoes are susceptible to fungal diseases such as blight, which can quickly spread throughout the garden if one plant is infected.

Lastly, when planted together, these two crops may compete for resources such as water and nutrients since they have similar root structures.


Walnut trees produce a chemical called juglone that can be toxic to other plants. This chemical is present in all parts of the tree, including the leaves, bark, and roots. When it gets into the soil, it can inhibit the growth of nearby plants. Tomatoes are especially sensitive to juglone toxicity and may wilt or die if planted too close to a walnut tree.

In addition to toxicity concerns, planting tomatoes with walnuts may attract pests like squirrels and chipmunks. These animals love walnuts and may dig up your tomato plants in search of buried nuts.

When planning your own companion garden, it’s important to consider which plants will complement each other best based on their growing habits and nutrient needs.

Here’s a quick table that provides information on plant varieties that shouldn’t be grown together with tomatoes and the reason why they are incompatible. 

Bad Companion PlantReason
Brassicas (e.g., Cabbage, Cauliflower, Broccoli)Attracts pests that can harm tomato plants and compete for nutrients
FennelInhibits growth and attracts pests
DillStunts tomato plant growth and attracts pests
PotatoesIncrease the risk of spreading blight
Walnuts (Walnut Trees)Produce juglone, which is toxic to tomato plants
EggplantCompetes for nutrients and spreads pests
CucumbersAttracts pests and competes for nutrients
CornA heavy feeder and competes with nitrogen intake
Rows of tomato and pepper plants in a garden.

Do tomatoes and peppers grow well together?

If you’re thinking about growing tomatoes and peppers together, you might wonder if they’ll work well together. The good news is that these two plants complement each other quite nicely in the garden. In fact, many gardeners recommend pairing tomatoes and peppers because they have similar soil requirements and growth habits.

One of the key benefits of growing tomatoes and peppers together is that they both prefer warm temperatures and plenty of sunlight. They also need similar soil conditions, including well-draining soil with a slightly acidic pH level. This means that if you properly prepare your garden bed for one plant, it will likely be suitable for the other.

Another advantage of planting tomatoes and peppers together is that they can help deter pests naturally. Tomatoes are known to repel certain insects like aphids, while peppers contain capsaicin which can keep away larger pests like rabbits or deer.

A basket full of ripe tomatoes and cucumbers.

Why should you not plant cucumbers near tomatoes?

Cucumbers and tomatoes belong to the same family of plants – Solanaceae – meaning they share similar pests and diseases. Planting them together can increase their susceptibility to these issues, leading to a lower yield or even crop failure.

This is especially true if one of the plants becomes infected with a disease such as Fusarium wilt or Verticillium wilt, which can spread quickly between the two crops.

Another reason why you should avoid planting cucumbers near tomatoes is that they compete for resources like water, nutrients, and sunlight. Although it may seem like a good idea to group similar plants together, these two veggies, in particular, don’t get along very well. In fact, planting them together could lead to some serious problems. 

If one plant gets infected, it’s likely that the other will too. This can lead to stunted growth, wilted leaves, and even the death of your beloved plants. Plus, once these pests and diseases take hold in your garden soil, they can be difficult to eradicate.

A pinterest image of tomatoes in the background, with the title "What are Bad Companion Plants for Tomatoes. The website's link is also included in the photo - gardenforbeginners.com

Planting the wrong companions with tomatoes can lead to stunted growth, poor yields, and increased susceptibility to diseases and pests. Plants that compete for nutrients, produce allelopathic chemicals, or attract harmful insects should be avoided.

Instead, consider planting beneficial companions like basil, marigold, or borage that improve soil fertility, deter pests, and enhance flavor. Although mixing and matching different vegetables in your garden may be tempting, it is important to consider their compatibility for optimal growth.

By following these guidelines, you can ensure that your tomato plants thrive and produce a bountiful harvest. Happy gardening!

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