Potatoes typically follow the standard plant cycle. The little plants develop into giant plants, two feet tall or more and up to three feet wide, and then the plants bloom in bunches at the top of the plant, either white or purple. When the blossoms fade and the plants begin to droop, the potatoes adhering to the roots should be of sufficient size. When the plant is still flowering, it is feasible to check for potatoes under the plants without pulling them up. You can carefully raise the plant, releasing the roots somewhat, and dig under it by hand. Small potatoes should be found on the roots towards the middle.