Potatoes are a fundamental crop cultivated globally, providing a versatile source of nutrition. Achieving a successful harvest requires attention to the timing of planting and digging. This guide outlines the steps and environmental conditions necessary to grow and store a plentiful potato crop, from preparing the seed potato to long-term storage.
Timing the Planting for Maximum Yield
Planting potatoes must be timed to avoid the last hard frost and ensure the soil is suitably warm for germination. Growers typically aim to plant two to four weeks before the average last spring frost date in their region. The seed pieces will rot if they are placed into cold, wet ground, so the soil temperature needs to be at least 45°F, with 50°F being preferable for quick, healthy growth.
A preparatory step called “chitting” encourages the development of short, sturdy sprouts before planting, leading to an earlier and more abundant harvest. Chitting involves placing the seed potatoes in a cool, light, and frost-free area for four to six weeks before planting. The light exposure ensures the sprouts are thick and green-purple, rather than long and weak.
The planting site should have loose, well-draining soil, ideally with a slightly acidic pH between 5.5 and 6.5. Compacted or overly alkaline soil can inhibit tuber formation and increase the risk of disease. Planting the chitted seed pieces in a prepared trench and covering them with a few inches of soil allows the soil to warm quickly.
Mid-Season Care for Tuber Development
Once the potato plants emerge and reach a height of approximately 8 to 12 inches, the practice of hilling begins. Hilling involves mounding soil, or another material like straw, around the base of the stems, leaving only the top leaves exposed. This action is repeated as the plant grows taller.
The primary purpose of hilling is to prevent developing tubers from being exposed to sunlight. Tubers exposed to light turn green, indicating the presence of solanine, a bitter compound toxic in large amounts. Hilling also encourages more stem growth underground, providing additional sites for new potatoes to form and increasing the overall yield.
Consistent soil moisture is important for growth, particularly during the two-week period when tubers are first forming. Water is especially needed when the plants begin to flower, which signals a phase of active tuber bulking. Tuber development slows or stops entirely if the soil temperature rises above 80°F, so maintaining adequate soil depth through hilling helps cool the soil.
Recognizing and Executing the Harvest
The timing of the harvest depends on whether the goal is to obtain small, tender “new potatoes” or fully mature “storage potatoes.” New potatoes are ready for harvest about seven to eight weeks after planting, often when the plant begins to flower. These are dug sparingly for immediate use, as their thin skins do not store well.
For the main crop intended for long-term storage, the plant must be allowed to reach full maturity. The sign of readiness is the natural yellowing and dying back of the plant’s foliage. Once the leaves and stems have completely died back, a waiting period of two weeks is necessary before digging.
This two-week interval allows the tuber skins to “set” or thicken, protecting the potato from damage and extending its storage life. Harvesting should be done on a dry day, using a spading fork to carefully loosen the soil several inches away from the plant base to avoid puncturing the tubers. Damaged potatoes should be set aside for immediate consumption, as they will not cure or store successfully.
Curing and Storing the Harvest
Immediately following harvest, potatoes must be cured to heal minor skin injuries and further thicken the skin. Curing involves placing unwashed potatoes in a dark space with high humidity (ideally 85 to 95 percent) and a moderate temperature of 50°F to 60°F for one to two weeks. This process minimizes water loss and inhibits the entry of decay-causing pathogens.
After the curing period, the potatoes are ready for long-term storage in a cool, dark environment. The ideal storage temperature is between 40°F and 45°F, which slows down the metabolic processes that cause sprouting. Temperatures below 40°F can cause starches to convert to sugars, leading to an undesirably sweet flavor.
Storage areas must maintain high humidity, around 90 percent, to prevent the tubers from shriveling, while remaining dark to stop greening. Light exposure causes the production of chlorophyll and solanine. Storing potatoes in ventilated containers, such as paper bags or crates, allows for necessary airflow while maintaining a dark, cool, and humid environment.