Potatoes are cool-season crops and can survive light frosts. Plant as soon as soil is workable in early spring. Potatoes need fertile, well-drained soil that’s loose and slightly acid (pH 5.8 to 6.5). Hard, compacted soil produces misshapen tubers. Amend heavy clay soil the fall before planting by working organic matter into planting beds. Potatoes form tubers 4 to 6 inches below the soil surface. When stems reach 8 inches tall, draw soil up and around plants, covering half of lower stems. Repeat the process two to three weeks later. Potatoes exposed to sunlight turn green, which causes flesh to taste bitter. Keeping tubers covered prevents greening.