When to harvest depends on what type of potato was planted. Early-season potatoes take approximately 60 to 70 days to mature; mid-season, approximately 80 days; and late-season, more than 90 days. The biggest and best potatoes, are harvested only after the foliage of the plant has died back. Cut browning foliage to the ground and wait 10 to 14 days before harvesting to allow the potatoes to develop a thick enough skin. Waiting too long to harvest can run the risk of rotting potatoes.
When harvesting, dig on a dry day; be be gentle with digging up so that the tubers are not punctured. Freshly dug potatoes need to sit in a dry and cool place for up to two weeks so the skins can "cure" which will let the potatoes last longer.
