Corn: Corn and tomatoes are both heavy feeders, competing for similar nutrients in the soil, which can lead to stunted growth and reduced yields for both plants.
Potatoes: Both tomatoes and potatoes are susceptible to similar diseases, such as late blight, so planting them together can increase the risk of disease spread.
Fennel: Fennel can inhibit the growth of tomatoes and affect their flavor. Additionally, tomatoes can inhibit the growth of fennel.
Brassicas: Brassicas can release compounds that inhibit the growth of tomatoes, and vice versa. Planting them together can negatively impact both crops.
Walnuts: Walnut trees and other members of the Juglans genus release juglone, a chemical compound toxic to many plants, including tomatoes.
Dill: Dill attracts tomato hornworms, which can be harmful to tomato plants. Additionally, dill can inhibit the growth of tomatoes when planted too closely.
Kohlrabi: Kohlrabi and tomatoes are both heavy feeders, and planting them together can result in competition for nutrients and reduced growth for both plants.
Sunflowers: Sunflowers can compete with tomatoes for sunlight, water, and nutrients, leading to reduced yields for both crops.
Beets: Beets can release compounds that inhibit the growth of tomatoes and other plants in the nightshade family.
Asparagus: Asparagus can produce allelopathic compounds that inhibit the growth of tomatoes and other nearby plants.