Potato plants (Solanum tuberosum) are among the most productive garden vegetables, produce nutritious tubers and are simple to grow. When the plants are harvested at the end of the growing season, some of the mature tubers can be saved for replanting as seed potatoes the next spring.
Immediately after harvest, cure the seed potato tubers for two weeks in a well-ventilated, dark location at about 55 to 60 degrees Fahrenheit and a relative humidity of 85 to 95 percent. Those conditions allow the tubers' skins to mature for longer storage. If the weather is dry, you may be able to leave the tubers in the garden to dry for one to two hours, but a temperature above 60 F or below 45 F will damage them, and excessive exposure to light will cause undesirable greening in them.
After curing the tubers, select the best ones for storage, and separate them from the ones you will eat. Gather the tubers you want to store, and place them in clean, sturdy cardboard boxes or paper bags. Tubers require ventilation. So don't layer them more than 6 to 8 inches high, and ensure their storage area is ventilated.
Store the tubers in the dark at 38 to 45 F and 90 percent humidity. Although the tubers require humidity, do not allow condensation to form on their surfaces because it may cause them to rot. A root cellar is an ideal storage location. You could also store them in a closet or sectioned-off corner of a room near an open vent, or dedicate a refrigerator to potato tuber storage.
Properly stored, seed potato tubers stay fresh for up to eight months, just in time to plant them the following spring.
Whether you buy seed potatoes from a supplier, garden center or Cooperative Extension Service office, or save your own potatoes to plant the following year, keep them in a cool, dark place until 10 to 14 days before planting them. Then during those 10 to 14 days, expose them to light and temperatures between 60 and 70 F to encourage sprouting.
Either plant whole seed potatoes that are at least 1 to 2 ounces, about the size of a chicken egg, or cut larger seed potatoes into pieces that size and plant them. Each seed potato or piece should have at least a few sprouts. Handle sprouting potatoes carefully so you don't break off the sprouts.
If you cut seed potatoes before planting, either plant the cut pieces immediately or allow their cuts to heal for one to two days in a dark location at 70 F and high humidity.