Potato - Seed Handling and Treatment
Always plant Foundation or Certified seed. Tubers or seed-pieces showing decay should not be planted. Store seed potatoes at 38-40°F and 95% relative humidity until planting, then warm tubers to 50-55°F for 2 weeks prior to cutting or planting. Cut seed can be planted immediately. If conditions after cutting delay planting, store seed stock in sacks or crates to allow air movement about them and keep in a humid environment for 2 or 3 days. Cut seed pieces should be blocky, have at least one eye, and weigh 1.5 - 2 oz. per piece. Seed pieces of uniform size and weight are easier to plant, so try to be consistent when cutting.
The ideal seedbed conditions for planting potatoes is warm soil, moderately moist, and of uniform particle size. Soils should be 50-60°F which encourages cut seed wound healing and rapid sprouting and emergence. Seed piece decay is more common when planted in cool (less than 45°F) wet soils.
Seed pieces can be pre-sprouted (called green sprouting or chitting) which accelerates plant emergence and speeds tuber development. Green sprouting combined with close plant spacing (about 6”) can lead to an earlier harvest by 7-14 days. Plants are commonly harvested when tubers are small and marketed as small new potatoes.
To green sprout seed, about 6 weeks prior to planting spread out seed tubers 1 layer deep with the eyes up. Seed should be chitted warm (~ 70°F) and at medium light intensities (bright shade - not direct sunlight). The warm stimulates strong shoots while the bright light keeps the shoots short. The sprouts should be about 1” long at planting. Do not cut the seed before green sprouting as this encourages desiccation.