The weather plays a big part of when I harvest my potatoes. If it is a wet year, the plants are actively growing and looking healthy I let them stay in the ground longer. If it is a dry year and the plants start to suffer, I pull them out. I plant over 100 seed potato, so I dig one up of each variety just to see how they look. If the potatoes are small, but the plants look healthy, I let them stay longer. If the potatoes are large and some are starting to grow, you need to harvest them. In my garden, the potatoes will get big and mature and then because it is cooler under the wood chips, they start to put out shoots/leaves and grow if I leave them too long. We eat the potatoes that have started to grow first, they don't keep well. My plants yield anywhere from 2 - 5 pounds per plant. I put in a drip line with 12 inch spacing giving out .5 gallon per hour of water, then I plant a potato on each emitter, I fertilize when I plant with bone meal, blood meal and chicken manure. When I hill the plants up the first time I top dress everything with chicken manure again. This year, my 120 plants gave me about 375 pounds of potatoes.