The potato is a popular and rewarding vegetable for home gardeners, but successful cultivation depends heavily on managing the depth at which it grows. Unlike many root vegetables, potatoes develop on underground stems called stolons, which emerge from the planted seed piece. The planting process is a series of actions designed to encourage maximum tuber formation while protecting the developing crop from sunlight. This method, which involves initial deep planting followed by continuous mounding of soil, is the key to a bountiful harvest.
Preparing the Seed Potato
The process begins with the seed potato. It is advised to use certified, disease-free seed potatoes rather than grocery store varieties, which may have been treated with sprout inhibitors. Potatoes smaller than a golf ball can be planted whole, but larger tubers should be cut into “seed pieces” roughly two inches square, ensuring each piece contains at least one or two visible buds, known as “eyes.” After cutting, these pieces should be allowed to “cure” or callous over in a cool, dry location for one to three days, forming a protective layer that prevents the seed piece from rotting in the moist soil.
Initial Trench Depth and Spacing
The first step is to prepare a trench between 6 and 8 inches deep. This initial depth helps protect the seed potato from late-season frost and ensures the surrounding soil remains consistently moist for initial root development. The seed pieces are placed cut-side down, eyes facing upward, and then covered with only 3 to 4 inches of soil, leaving a partial trench to be filled later as the plant grows. Proper spacing is important; each seed piece should be placed about 10 to 15 inches apart within the trench, allowing sufficient space for the plant to develop a strong root system and form new tubers.
The Process of Hilling
The depth of the potato is managed through a process called “hilling” or “earthing up.” Hilling involves continuously adding soil or organic mulch, such as straw, around the base of the plant’s stem as it grows above ground. This practice should begin when the plant stems are about 6 to 8 inches tall, mounding the soil up until only the top few leaves are visible. Hilling serves two primary purposes. First, burying more of the stem encourages the plant to produce more stolons, increasing the overall yield, since edible tubers develop along these underground stems. Second, hilling shields the developing tubers from sunlight exposure, which prevents them from producing the toxic compound solanine, indicated by the skin turning green.
Timing the Harvest
Determining the right time for harvest depends on the desired type of potato. Gardeners can harvest “new potatoes,” which are small, immature tubers with thin skins, two to three weeks after the plants begin to flower. These smaller potatoes are best for immediate consumption because their delicate skins do not lend themselves to long-term storage. For mature, storage potatoes, wait until the plant’s foliage naturally yellows and dies back, indicating the plant has redirected its energy into the tubers. Once the foliage has died back, wait an additional two weeks before digging up the tubers, allowing the skins to fully harden for long-term storage.