Bad Companion Plants for Tomatoes: What You Need to Know

The Importance of Companion Planting

Companion planting is the practice of growing different types of plants together in a way that benefits both. For example, some plants can attract beneficial insects or repel harmful ones, while others can add nutrients to the soil or improve its structure. The goal is to create a diverse ecosystem that supports healthy growth and minimizes pest and disease problems.

Tomatoes are one of the most popular garden vegetables, but they can also be vulnerable to pests and diseases. Choosing the right companion plants can help mitigate these risks, but it's important to avoid certain combinations that can actually harm your tomato plants. In this article, we'll explore some of the worst companion plants for tomatoes and explain why they should be avoided.

The Top 10 Worst Companion Plants for Tomatoes

1. Brassicas (Cabbage, Broccoli, Cauliflower)

Brassicas are members of the cabbage family and include vegetables like broccoli, cauliflower, kale, and Brussels sprouts. While these plants are generally easy to grow and highly nutritious, they can attract pests like aphids and whiteflies that can also attack tomato plants. Additionally, brassicas and tomatoes have similar nutrient requirements, so planting them together can deplete the soil more quickly.

2. Nightshades (Peppers, Eggplant, Potatoes)

Nightshades are a group of plants that includes peppers, eggplant, and potatoes, as well as tomatoes. While these plants are all related and have similar growing requirements, planting them together can increase the risk of diseases like blight and verticillium wilt. Additionally, some species of nightshades can host pests that also attack tomatoes, such as flea beetles.

3. Fennel

Fennel is a herb with feathery leaves and a licorice-like flavor. While it can be a great addition to many dishes, it's not a good companion for tomato plants. Fennel produces chemicals that can inhibit the growth of other plants, including tomatoes. It can also attract pests like aphids and spider mites that can harm your tomatoes.

4. Corn

Corn is a staple crop in many parts of the world, but it should not be planted near tomato plants. Corn can attract pests like corn earworms and armyworms that can also attack tomatoes. Additionally, corn and tomatoes have similar nutrient requirements, so planting them together can deplete the soil more quickly.

5. Walnuts

Walnut trees produce a chemical called juglone that is toxic to many plants, including tomatoes. If you have walnut trees on your property, it's best to plant your tomatoes elsewhere or in containers. Be aware that juglone can remain in the soil for several years, so it may be necessary to test the soil before planting tomatoes in an area where walnuts previously grew.

6. Dill

Dill is a popular herb used in many cuisines, but it can be a bad companion for tomatoes. Like fennel, dill produces chemicals that can inhibit the growth of other plants, including tomatoes. It can also attract pests like tomato hornworms and aphids that can harm your tomatoes.

7. Strawberries

Strawberries are a delicious fruit, but they can be a bad companion for tomato plants. Strawberries are susceptible to many of the same diseases as tomatoes, including verticillium wilt and fusarium wilt. Additionally, both strawberries and tomatoes attract pests like spider mites and aphids.

8. Kohlrabi

Kohlrabi is a member of the cabbage family and has a bulbous stem that can be eaten raw or cooked. While it's not a common garden vegetable, it can still be a bad companion for tomato plants. Kohlrabi attracts pests like flea beetles and can also deplete the soil of nutrients.

9. Cucumbers

Cucumbers are a popular summer vegetable, but they should not be planted near tomato plants. Cucumbers are highly susceptible to diseases like downy mildew and powdery mildew that can also affect tomatoes. Additionally, cucumber beetles can spread bacterial wilt, which can kill tomato plants.

10. Sunflowers

Sunflowers are a beautiful addition to any garden, but they can be a bad companion for tomato plants. Sunflowers produce chemicals that can inhibit the growth of other plants, including tomatoes. They can also attract pests like aphids and whiteflies that can harm your tomatoes.

Additional Tips for Companion Planting with Tomatoes

While it's important to avoid planting certain crops near tomatoes, there are also some plants that can be beneficial companions. Here are a few tips for successful companion planting with tomatoes:

1. Plant Herbs Near Tomatoes

Many herbs have natural pest-repellent properties and can help protect your tomato plants. Some good choices include basil, parsley, thyme, and oregano.

2. Use Flowers to Attract Beneficial Insects

Flowers like marigolds, zinnias, and calendula can attract beneficial insects like ladybugs and lacewings that prey on garden pests.

3. Rotate Your Crops

Rotating your crops each year can help prevent soil-borne diseases from building up in the soil. Try to avoid planting tomatoes in the same spot more than once every three years.

4. Use Mulch to Conserve Moisture and Suppress Weeds

Mulching around your tomato plants can help conserve moisture in the soil and suppress weeds. Good choices include straw, leaves, and grass clippings.

5. Water Consistently and Deeply

Tomatoes need consistent moisture to grow well, so be sure to water them deeply and regularly. Avoid getting water on the leaves, as this can promote the growth of fungal diseases.

Frequently Asked Questions About Companion Planting with Tomatoes

1. What are the benefits of companion planting with tomatoes?

Companion planting can help improve soil health, reduce pest and disease problems, and increase yields. By choosing the right companion plants, you can create a diverse ecosystem that supports healthy growth and minimizes risks.

2. Can I plant peppers and tomatoes together?

While peppers and tomatoes are both nightshades, they should not be planted together. They have similar nutrient requirements and are susceptible to many of the same diseases. Additionally, some pests that attack peppers can also harm tomatoes.

3. Can I plant tomatoes near cucumbers?

It's best to avoid planting tomatoes near cucumbers, as they are susceptible to many of the same diseases. Additionally, cucumber beetles can spread bacterial wilt, which can kill tomato plants.

4. How do I know if my soil is depleted?

If your soil is depleted, your plants may be smaller than usual and produce fewer fruits or vegetables. Additionally, the leaves may be pale or yellowish and the plants may be more susceptible to pests and diseases.

5. Can I plant tomatoes near garlic?

Garlic can be a good companion for tomatoes, as it repels some pests like aphids and spider mites. However, be aware that garlic has a strong odor and flavor that can affect the taste of nearby crops.