Start with a good quality, commercial potting soil that is high in organic matter. This will insure that the soil is sterile and pest-free.
Prepare the container by putting a 4” (10cm) layer of soil in the bottom of the bag. Place from 2-5 seed potatoes on the soil spacing them as evenly as possible from each other and from the sides of the bag. Next cover the potatoes with a 3-6” (8-15cm) layer of soil and water well. Every time the plants reach 2-3” (5-8cm) in height they should be covered again with more soil. Be sure to water the existing soil before adding the new layer of soil.
Once the soil level is to the top of the bag, the foliage can be allowed to grow through the rest of the season. At the end of the season, when the foliage starts to turn pale green to yellow, watering can be discontinued. The potatoes will continue to grow until the plant is fully wilted.
To harvest, just clear away the wilted foliage, empty the entire bag onto the ground or a tarp and remove the potatoes. To store the potatoes just wipe them off and allow them to dry for a day. It’s best not to wash potatoes until just before they are going to be used.
Take care not to damage the potatoes while moving them to storage. Bruises and cuts on a potato can be an invitation to bacteria, fungus, and pests that can lead to rot. A mesh or paper bag is a good choice for holding potatoes as both allow for good air circulation. The potatoes will keep longest if stored in a cool, dark, well ventilated location. A consistent temperature between 50-60° F (10-15° C) is ideal. Any potatoes that turn soft, shriveled or that are starting to sprout should be removed.