What NOT To Plant With Tomatoes: 5+1 Plants That Shouldn’t Share A Tomato Bed

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what not to plant with tomatoes

Before you grab your gardening gloves and start planting your tomato seedlings, there’s something you need to know: what NOT to plant with tomatoes.

There are certain plants that just don’t get along with them. Planting the wrong companions can lead to stunted growth, pest infestations, and even diseases. Just keep reading to learn 5 don’ts of tomato companions!

Companion planting is a gardening technique that involves planting different species of plants together in order to enhance their growth and overall health. It is especially beneficial for tomato plants as it can help improve their yield, pest resistance, and flavor.

However, it is crucial to be aware of plants that may have negative effects on tomatoes and avoid planting them together.

Some plants have allelopathic properties, meaning they release chemicals that can inhibit the growth of other plants. Examples of plants that should be avoided as companions to tomatoes include members of the Brassica family, such as cabbage and broccoli, as well as potatoes.

Now let’s see 5+1 plants that don’t go well with tomatoes.

1. Potatoes (And Other Nightshades)

what not to plant with tomatoes - potato

Potatoes and tomatoes are both members of the nightshade family, Solanaceae (it also includes peppers and eggplant). This means they share several common characteristics, including a susceptibility to the same pests and diseases.

When planted together, these two crops can have a significant impact on each other’s health and overall yield. One notable threat they are prone to is blight, a fungal disease that affects both potatoes and tomatoes.

By planting them in close proximity, the chances of blight spreading from one plant to another increase substantially.

Another issue that arises from planting potatoes and tomatoes together is the competition for resources. Both plants require similar nutrients and water to thrive, and planting them side by side can lead to reduced yields due to limited availability of these essential elements.

Furthermore, planting these two crops together can create a breeding ground for common pests that target the nightshade family. Insects such as aphids, Colorado potato beetles, and tomato hornworms often infest potatoes and tomatoes, causing extensive damage to the plants.

When planted in close proximity, these pests can easily move from one plant to another, exacerbating the problem and making it harder to control the infestation.

To mitigate these risks, it is advisable to separate the planting of potatoes and tomatoes by a significant distance. This separation helps reduce the chances of disease transmission, as well as minimizes competition for resources.

2. Cabbage Family (Cabbage, Broccoli, Cauliflower)

what not to plant with tomates - cabbage

The cabbage family (Cruciferous vegetables), which includes popular vegetables such as cabbage, broccoli, and cauliflower, is known to attract common pests such as cabbage worms and aphids.

These pests have a tendency to spread from the cabbage family plants to other nearby plants, including tomato plants.

Cabbage worms are particularly attracted to the leaves of cabbage, broccoli, and cauliflower. They feed on the foliage, leaving behind unsightly holes and damage.

If left untreated, the cabbage worms can quickly multiply and infest neighboring tomato plants. This can lead to a decline in the overall health and productivity of the tomato plants.

Aphids, on the other hand, are tiny insects that feed on the sap of the cabbage family plants. They can easily move from one plant to another, spreading disease and causing damage along the way.

Tomato plants are susceptible to aphid infestations, and if infected, they may exhibit stunted growth and produce lower-quality fruits.

Cross-contamination is a significant concern when it comes to the cabbage family and tomato plants. When pests like cabbage worms and aphids infest the cabbage family plants, they can easily transfer to tomato plants planted nearby. Cross-contamination can have detrimental effects on the growth and quality of tomatoes.

Pests like cabbage worms and aphids not only cause physical damage to the tomato plants, but they can also introduce diseases. Infected fruits may have blemishes, discoloration, or an unpleasant taste, making them less desirable for consumption.

3. Corn

what not to plant with tomatoes - corn

Corn, scientifically known as Zea mays, is a staple crop globally, cultivated for its versatile use as food, animal feed, and even in biofuel production.

However, when considering its cultivation alongside tomatoes, several crucial issues must be addressed. One prominent problem is the competition for nutrients between the two plants.

Corn is known to be a heavy feeder, meaning it demands a substantial amount of nutrients from the soil in order to grow and thrive. This high nutrient requirement can potentially deprive nearby tomato plants of the essential resources they also need for healthy development.

The height of corn plants can also create a challenge for tomatoes. As corn matures, it can reach towering heights, forming a dense canopy that blocks sunlight from reaching smaller companion plants like tomatoes.

When tomatoes are shaded by tall corn plants, they receive limited access to sunlight, leading to stunted growth and reduced fruit production.

Providing adequate distance ( min. 8-10 ft / 2.5-3 m) between corn and tomato plants helps minimize nutrient and sunlight competition.

If you have limited space, employing trellises or stakes for tomato plants can enable them to grow vertically, away from the overshadowing effects of corn.

4. Fennel

what not to plant with tomatoes - fennel

Fennel, scientifically known as Foeniculum vulgare, is a flavorful and aromatic herb that is commonly used in cooking and for medicinal purposes.

While it is a versatile and valuable addition to any herb garden, it is important to note that fennel should be kept away from tomatoes. This is primarily due to its allelopathic nature, which means that it produces chemicals that can inhibit the growth and development of other plants, including tomatoes.

The chemicals produced by fennel can act as natural herbicides, inhibiting the germination and growth of neighboring plants. This can lead to stunted growth, nutrient deficiencies, and even death in severe cases.

Another reason to keep fennel away from tomatoes is the potential impact on flavors. Fennel is known for its strong aroma and distinct taste, which comes from its high concentration of essential oils.

These aromatic compounds can easily transfer to neighboring plants, including tomatoes, and interfere with their natural flavors.

5. Dill

what not to plant with tomatoes - dill

Dill is a commonly used herb in the culinary world, known for its distinctive taste and aroma. While it is generally considered a beneficial companion plant, it can have a negative impact on the growth of tomatoes.

This is primarily due to dill’s tall and bushy nature, which can overshadow the tomato plants and inhibit their access to sunlight. Tomatoes require ample sunlight for photosynthesis, and the shade caused by dill can hinder their growth and development.

Dill’s strong aroma can also attract pests like aphids. Aphids are small, sap-sucking insects that feed on the sap of plants, causing damage and sometimes even transmitting diseases.

The scent of dill can act as a magnet for aphids, drawing them towards the tomato plants. Once aphids infest the tomato plants, they can cause significant harm by feeding on the plant’s sap and potentially spreading diseases.

Consider planting dill at a distance from your tomato plants, ensuring that it doesn’t overshadow them. This will allow the tomatoes to receive adequate sunlight and prevent competition for resources.

You can also prune dill regularly to keep its size in check and prevent it from encroaching upon the tomato plants.

+1: Walnut Trees

Walnut trees, including black walnut, release a chemical called juglone, which inhibits the growth of many plants, including tomatoes.

When tomatoes are planted near a black walnut tree, they may exhibit stunted growth, yellowing of leaves, and reduced fruit production.

It is best to avoid planting tomatoes in close proximity to black walnut trees in order to avoid these negative effects.


Tomatoes are a popular and widely consumed crop that can thrive in a variety of growing conditions. However, when certain plants are planted together with tomatoes, they can have negative effects on their growth and health.

These include potatoes, nightshades, corn, fennel, and dill. Planting near black walnut trees should also be avoided.

FAQ About What Not To Plant With Tomatoes

Can I plant potatoes near tomatoes?

Planting potatoes near tomatoes is generally not recommended as they have similar nutrient requirements. When planted together, they may compete for nutrients in the soil, leading to stunted growth and reduced yields. Additionally, potatoes are prone to certain diseases, such as late blight, which can easily spread to tomatoes if they are in close proximity. It is advisable to maintain a distance of at least 4-6 feet (120-180 cm) between tomatoes and potatoes to avoid these issues.

Is it safe to grow cucumbers alongside tomatoes?

Cucumbers can be grown alongside tomatoes, but it is important to consider a few factors when deciding their placement. Both vegetables are heavy feeders, meaning they require ample nutrients from the soil. Ensure that the soil is well-nourished and add organic matter to promote healthy growth. Providing trellises or cages for both plants will help maintain good air circulation and prevent sprawl. Make sure cucumbers don’t climb with their vines on the tomato plants.

What should I avoid planting near tomatoes?

When considering what not to plant with tomatoes, it is best to avoid growing members of the nightshade family nearby (peppers, eggplants, and potatoes). Other plants, such as corn and sunflowers, should also be kept at a distance from tomatoes. These taller plants can cast shadows over the tomatoes, depriving them of essential sunlight. Moreover, plants that attract pests or have invasive roots should be kept away from tomatoes to ensure optimal growth.

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I'm a keen hobby gardener. I love growing fruits and vegetables, especially tomatoes. I'm also a certified instructor of the Square Foot Gardening Foundation.