What Part of the Plant Do Potatoes Come From?

Growth Process

• Potatoes start out below the soil as whole seed potatoes or sections of seed potatoes that contain "eyes," or blossom chits. These usually are evident as sprouts growing from small depressions in the potato's outer skin. On potatoes that have been stored awhile, the sprouts often start to elongate and in some cases produce small pink leaves on greenish-white stems. Once planted, however, seed potatoes or sections produce roots and shoots almost simultaneously from the same eyes. As the root travels down into the soil, the shoot pushes above ground, sprouts leaves, and begins manufacturing food through the process of photosynthesis. The plants capture sunlight, causing a chemical reaction in the cells that produces sugars and starches. At first, all parts of the plant benefit, but once flowering has begun, only certain sections of the roots continue growing, resulting in potatoes.

Growth Stages

• During the first three growth stages, two types of roots form below the soil, and the original seed or section decomposes. Fibrous roots are true roots designed to extract moisture and nutrients from the soil, while stolons are not really roots, but extensions of the potato plant's stems that grow into the soil. Tiny new potatoes, or tubers, develop at the tips of the stolons during the second and third stages, but significant growth does not begin until the fourth stage when the tubers become the focal point for the deposition of starches, or carbohydrates. Stage five marks the culmination of the process, as the potato plants turn yellow, and photosynthesis and tuber growth slow down. As the plant dies, the skins on the potatoes thicken until they are harvested.

Culture

• Potatoes need rich, loose well-drained soil and get their best start during cool weather, or about 2 weeks after the last spring frost. Two to four inches of aged compost should be worked into the top 6 inches of soil, along with 1.5 pounds of all purpose fertilizer for every 100 feet of row. Whole seed potatoes can be planted immediately, but cut pieces containing at least 2 or 3 eyes should be allowed to dry for 1 to 2 days, which increases their resistance to premature rotting. Potatoes should be planted eye-side up about 4 inches deep and 6 to 12 inches apart with 3 feet apart between the rows. Potatoes need moisture especially during tuber formation and should receive 1 to 2 inches of water per week. Insufficient moisture may produce abnormal growth, such as knobs or cracks on the skin.

Special Notes

• While potato plants need sunlight to grow, the tubers themselves should be protected from it. This can be achieved by a process known as hilling, which involves bringing the soil up around the base of the plants within four weeks of planting or when they are about 6 inches tall. Hilling should be done every two weeks to keep the developing tubers safely covered. A thick layer of straw, leaves or compost also can be built up at the base of the plants to protect the potato roots during the tuber growth state.