Buy certified disease-free seed potatoes from your local garden center. Quarter them with a paring knife; each piece should contain at least one eye. Dust the pieces with a rot-preventing fungicide recommended by your local Cooperative Extension Service. Spread them out in the sun; let their cut sides dry hard.
Prepare a rectangular bed in light, sandy, well-drained, and slightly acidic soil. Cultivate 4 inches deep: add compost and well-rotted manure; further enrich the soil with a 5-10-5 fertilizer.
About 20 days before the last frost date in your area, lay the dried pieces in rows, cut side down, eyes up, on the surface of the bed. Allow about 1 foot between pieces in all directions. Press them firmly into the soil, then cover with 6 to 8 inches of hay. Moisten the hay to keep it from blowing away. The potatoes should sprout in 20 days. If frost threatens, cover the sprouts with mulch.
Start harvesting young potatoes 7 to 8 weeks later, when blooming begins. Probe the soil with your fingers, taking care not to disturb the plants or the mulch.
If you see signs of blight-purple blotches on the leaves-spray weekly with maneb. Your crop is full-grown when vine leaves wither. Harvest all potatoes before the first frost.