There are many different companion plants that can be grown alongside tomato plants. Some good options include basil, parsley, chives, marigolds, and borage. These plants help to improve the growth and health of tomato plants by repelling pests and providing nutrients. Additionally, planting tomato plants with other types of vegetables like peppers, eggplants or potatoes can help to improve the flavor of the tomatoes. Choosing a spot that tomatoes were not grown in the last year is also important to maximize soil nutrients!