Potato pieces, also called seed potatoes, are typically cured for a couple of days before being planted with the eyes facing up. Planting them while they are freshly cut invites disease and rot for the seed potato pieces.
When potatoes grow, the stems shoot upward from the eyes in the planted seed potato pieces. Planting them with the eyes facing up helps guide potato seedlings so they can break through the soil toward the sun.
Seed potato pieces should be buried at a depth of about 3 to 4 inches, about two weeks before the date of the last frost in a gardener's planting zone. Potato plants grow best in cooler weather, but because frost can kill them, it is best to grow them in the spring rather than the fall.
Gardeners should avoid having more than two eyes per seed potato piece when planting. Even when planted so that all eyes point up, multiple potato plants growing from the same seed potato will crowd each other and be less productive.