The answer varies depending on the tomatoes you are planting. If you are planning to use containers, choose compact and small tomatoes. They can reach a width of about two feet, but they won’t grow particularly high in size. Most tomato types, however, require more space. The plant’s roots can become as much as six inches wide. That is why staking the roots is recommended to ensure optimal growth conditions. While you are planting tomatoes into the soil, try to put two-thirds of the entire plant under it. The only parts above the surface should be the leaves. Root development is vital for tomatoes, which is why this is the optimal way of planting them.