Your may begin to harvest your potatoes 2 to 3-weeks after the plants have finished flowering. At this time you will only find small "baby" potatoes if you were to dig up a plant. Potatoes can be harvested any time after this, by gently loosening the soil, reaching under the plant, and removing the largest tubers, leaving the smaller ones to continue growing.
If you want late potatoes for storage, wait 2-3 weeks after the foliage dies back. Carefully begin digging a foot or so outside of the row or mound. Remove the potatoes as you find them. (Be careful not to bruise or cut the tubers with your spade!) If the weather is dry, allow the potatoes to lay on the soil surface, unwashed, for 2-3 days so they can dry. If the weather is wet, or rain is expected, move the harvest to a cool, dry area (like a garage or basement) for the drying period. This drying step is necessary to mature the potato skin, which will protect the potato during storage.
If, by the end of September, the plants have not begun to die back, all of the foliage should be cut off to ensure your crop has ample time to mature before winter.
