Potatoes grown for winter use should be harvested after the vines have died and the crop is mature. To check maturity, dig up one or two hills of potatoes. If the skins on the tubers are thin and rub off easily, the crop is not fully mature and will not store well. Wait a few more days before harvesting. The skins on mature potatoes remain firmly attached to the tubers. Avoid bruising, skinning, or cutting the tubers during harvest. Damaged potatoes should be used as soon as possible.
Before placing the potatoes in storage, the tubers should be cured. Cure potatoes at a temperature of 50 to 60 degrees F and a relative humidity of 85 to 90 percent for two weeks. Healing of minor cuts and bruises and thickening of the skin occurs during the curing process.
Once cured, sort through the potatoes and discard any soft, shriveled, or blemished tubers. Soft or blemished potatoes may spoil in storage and destroy much of the crop. Potatoes should be stored at a temperature of 40 degrees F and relative humidity of 90 to 95 percent. Store the tubers in a dark location as potatoes turn green when exposed to light. If storage temperatures are above 50 degrees F, the potatoes will start to sprout after two or three months. When stored below 40 degrees F, potatoes develop a sugary, sweet taste. Sugary potatoes may be restored to their natural flavor by placing them at room temperature for a few days prior to use. Do not allow potatoes to freeze.
A root cellar or a second refrigerator (set a few degrees higher than normal) are excellent storage sites for potatoes. Other possibilities include a cool basement, spare (unheated) room, or insulated garage. Do not store potatoes with apples or other fruit. Apples and other fruit give off ethylene gas which may promote sprouting of potatoes.