For storage potatoes, begin harvest after the vines have died back naturally on their own and have been dead for about two weeks. To check maturity, dig up one or two test hills of potatoes. The skins on mature potatoes should remain firmly attached to the tubers when rubbed with a finger. 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.
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Potatoes can tolerate a light frost, 30 to 32 degrees, while still in the ground, but heavier frost will affect potato quality and shorten their storage life. Freezing temperatures cause the potato flesh to turn gray or black.
Choose a warm, dry day to harvest. With a spading fork, dig up the hills being careful to dig far enough away from the main plant to avoid bruising, skinning, or cutting the tubers. Gently brush off a majority of soil, but do not wash them. Washing decreases storage life and increases the potential for rots.
Sort out any potatoes damaged during harvest and use them for fresh eating as soon as possible. Damaged potatoes are likely to rot in storage.
Curing and storage
Before placing potatoes in storage, the tubers should be cured. Cure potatoes at a temperature of 45 to 60 degrees and high relative humidity (85-95%) for two weeks. Healing of minor cuts and bruises and thickening of the skin occurs during the curing process. Use perforated plastic bags to provide the high humidity needed during curing.