Plant potato seed pieces, weighing at least 2 ounces and having at least one eye, once the ground has thawed and the soil has warmed. Harvesting time varies, depending on your desire for "new" or "mature" potatoes.
If cutting your seed pieces into smaller portions, do so 24 hours before planting, so the cuts may dry and prevent rot. When planting the seed pieces, place the piece cut side down in holes 3 to 5 inches deep. Cover the seed pieces with at least 4 inches of soil or mulch. Individual seed pieces should be spaced 10 to 12 inches apart, with planting rows being spaced 30 to 36 inches apart.
As plant emerges, hill the soil up around the base of the plant. The growing tubers should be kept immersed in soil, as direct sunlight causes the tubers to discolor. Water the potato plants at least once a week, more frequently if your soil is sandy and drains quickly. Water to a depth of 1 inch below the surface to encourage strong root development.
Harvest "new" potatoes seven to eight weeks after planting. These potatoes are smaller and with thinner skins. Mature, larger potatoes can be harvested at the end of the growing season, once the plant's leaves have dried up. Carefully use a garden fork to dig up soil at the base of the plant. Use caution not to spear the potatoes.