Corn: Corn and tomatoes are both susceptible to similar pests and diseases, such as corn earworm and tomato hornworm. Planting them together can attract these pests and increase the risk of infestation.
Potatoes: Both tomatoes and potatoes belong to the nightshade family and are susceptible to similar diseases, such as blight. Planting them together can increase the risk of spreading diseases and decrease overall crop yields.
Brassicas (Cabbage, Broccoli, Cauliflower): Brassicas can compete with tomatoes for nutrients in the soil and may stunt their growth. Additionally, tomatoes can attract pests like cabbage worms, which can also damage brassica crops.
Fennel: Fennel produces chemicals that can inhibit the growth of nearby plants, including tomatoes. Planting tomatoes near fennel may result in poor growth and reduced yields.
Walnut Trees: Walnut trees release a chemical called juglone into the soil, which can be toxic to many plants, including tomatoes. Avoid planting tomatoes near walnut trees or using walnut tree leaves or wood chips as mulch.
Kohlrabi: Kohlrabi is a member of the brassica family and can compete with tomatoes for nutrients and space in the garden. Planting them together may result in decreased yields for both crops.
Pumpkins and Squash: Pumpkins and squash can spread rapidly and may shade out tomato plants, reducing their access to sunlight and inhibiting their growth.