The tuber commonly known as the Irish potato is scientifically identified as Solanum tuberosum, one of the world’s most widely grown crops. The name references the potato’s significance in 19th-century Ireland, but its origin traces back to the Andes Mountains of South America. Cultivating these tubers at home requires a practical approach to maximize yield and quality. This guide covers the process from initial preparation to harvest and storage.
Preparing the Seed Potatoes and Soil
The process begins with selecting certified disease-free seed potatoes. Using certified stock avoids introducing soil-borne pathogens and viral diseases into the garden. If a tuber is larger than a chicken egg, cut it into pieces weighing 1.5 to 2 ounces, ensuring each piece contains at least one or two “eyes,” the nodes from which sprouts will grow.
Before planting, gardeners often “chit” or pre-sprout their seed potatoes. This involves placing the seed pieces in a cool, bright, frost-free location for several weeks until short, sturdy sprouts emerge from the eyes. Chitting activates the tuber’s growth cycle, leading to quicker emergence once planted. Allow the cut surfaces to dry and form a protective layer, or “scab,” for a day or two before planting.
Potatoes thrive in deep, loose, well-drained soil. Incorporating organic matter like compost or well-rotted manure is beneficial, as heavy clay soils can lead to tuber rot. The ideal soil pH is slightly acidic, ranging between 5.0 and 6.0, which helps suppress the common potato scab disease.
Planting Methods and Timing
Potatoes are a cool-season crop. The optimal time for planting is early spring, two to three weeks before the average last frost date. Planting too early into cold, wet soil can cause the seed pieces to rot. The soil temperature should be at least 45°F (7°C).
For row planting, dig a trench 6 to 8 inches deep in the prepared soil. Place the chitted seed pieces cut-side down, spacing them 10 to 12 inches apart within the trench. Space multiple rows 30 to 36 inches apart to allow room for hilling and maintenance.
Cover the seed potatoes with 3 to 4 inches of soil initially, leaving the rest of the trench unfilled. This shallow covering encourages rapid emergence. Water the plants sparingly until the shoots break the soil surface.
Hilling and Mid-Season Maintenance
Hilling, also known as earthing up, is a necessary practice that protects developing tubers from light exposure. Tubers exposed to sunlight turn green and produce solanine, a toxic compound that makes them inedible. Hilling also encourages the plant to produce more tubers along the buried portion of the stem, increasing the potential yield.
The first hilling should occur when the potato plants are 6 to 8 inches tall. Use a hoe or shovel to draw loose soil and pile it up around the base of the plant, covering the stems until only the top few inches of foliage remain exposed. Repeat this process every two to three weeks, or whenever the new growth reaches 6 to 8 inches above the existing soil mound.
Continue hilling until the mounds reach a height of 12 to 15 inches. During active growth, consistent moisture is important, especially when the plants are flowering and setting tubers. Potato plants require about 1 inch of water per week; irregular watering can lead to misshapen or cracked tubers. Supplementing with a balanced fertilizer, applied as a side dressing, supports the nutrient demands of tuber formation.
Harvesting and Curing for Storage
Harvest time is signaled when the foliage begins to yellow, wither, and completely die back. This process, called senescence, indicates that the plant has finished growing and the tubers have reached maturity. About two weeks before the planned harvest, stop watering the plants to allow the soil to dry out and the potato skins to thicken, which improves storage life.
To harvest, carefully use a garden fork or shovel, inserting it several inches away from the center of the dead plant to avoid piercing the potatoes. Gently lift the entire plant and surrounding soil to expose the tubers. Potatoes with nicks or cuts should be set aside for immediate consumption, as they will not store well.
The final and most important step for long-term storage is curing, a process that heals minor wounds and toughens the skin. Spread the freshly dug potatoes in a dark, well-ventilated area with high humidity and a moderate temperature, between 45°F and 60°F (7°C and 15°C). After 10 to 14 days, the skins will be firm and resistant to rubbing, indicating the curing is complete. The cured potatoes should then be transferred to a cool, dark, and humid storage location, with temperatures maintained between 40°F and 46°F (4°C and 8°C) for maximum longevity.