CORVALLIS, Ore. – Would you like your homegrown potatoes to stay fresh and last longer? Research has shown there are best practices to harvesting and storing potatoes to ensure freshness, according the Oregon State University Extension Service.
"Toughen up potatoes for storage before harvest by not watering them much after mid-August," said Alvin Mosley, a retired OSU Extension Service potato researcher. "Let the vines die all the way back before you harvest them."
Clean potatoes before storing them. You need only brush off the soil on potatoes grown in coarse, sandy soil. But if the soil is fine, sticky clay, your potatoes may need washing. If so, be sure they are completely dry before placing them in storage. Minimize tuber exposure to light while cleaning.
Cure newly dug and cleaned potatoes for a week to 10 days in a dark, well-ventilated area with moderate temperatures and high humidity, and they will last longer. After curing, slowly drop the storage temperature to about 40 to 45 degrees for table use. Potato tubers are about 80 percent water, depending on the variety, so high storage humidity is recommended to prevent shriveling.
Storage temperatures below 45 degrees can cause sugar buildup or sweetening. Fried products from such tubers are darker and oilier than those from tubers stored at higher temperature. While low temperatures can ‘sweeten’ tubers, high temperatures often lead to excessive decay, shriveling and sprouting.
Sort out and cull injured and diseased spuds before storing them long-term. Store only healthy potatoes in well-ventilated containers. Eat the ones hit by your shovel and those with bad spots or disease in the first month or so after harvest, as injured potatoes don't last. They also may spread spoilage or disease microorganisms to other potatoes.
Make sure to keep the storage area dark as light will turn tubers green and make them unfit for table use. The green color is caused by chlorophyll, common to all green plants. Chlorophyll is harmless but is frequently accompanied by high levels of a toxic alkaloid called solanine. While small quantities of solanine are harmless, too many green potatoes can lead to illness. Therefore, discard all potatoes with excessive greening.
Grow potatoes that keep well. Red potatoes usually don't keep as long as yellow or white varieties. Thin-skinned potatoes don't last as long in storage as those with thick skins, such as russets. Late-maturing varieties almost always store better than early types.
"With proper storage, well-matured potatoes will stay in good condition for seven to eight months," Mosley said. When storage temperatures exceed 45 degrees, potatoes should keep for two to three months, but sprouting and shriveling may occur.
"Planting sprouted, shriveled tubers the following spring is not recommended because of excess disease levels, particularly viruses," Mosley said. "Certified seed doesn’t cost, it pays. Whenever possible, plant only certified, healthy seed potatoes."