The tomato plant has a root system called a taproot. This structure allows the plant to grow downward into the soil. As the taproot grows downward, the roots of the plant can stretch to reach water and nutrients below the surface. However, as the plant gets older, its taproot begins to die off. The top of the taproot is called the crown. At this point, the plant may grow upward, but the taproot is no longer able to support the plant.