Potatoes are ready to harvest when the vines are about half dead.
Potatoes dug too early have tender skins and are easily bruised.
Delaying digging will allow the soil to heat because it is no longer shaded by foliage. High soil temperatures can lead to sprouting potatoes. Allow potatoes to “set” by keeping them in a shady, dry location for a day or so. Move them to a cool, moist environment such as a cellar or cool basement for longer storage. (Ward Upham)
