You can grow new potatoes from an existing potato. This practice leverages the potato’s unique biological structure, which is a modified stem called a tuber, not a true seed. Unlike many vegetables that reproduce sexually, the potato uses vegetative propagation to multiply. This asexual method allows the gardener to clone the parent plant, ensuring the resulting potatoes possess the same desirable characteristics.
The Science of Tuber Propagation
The potato tuber functions primarily as a storage organ for starch and nutrients, designed by the plant for survival and asexual reproduction. Surface indentations known as “eyes” are dormant axillary buds, which are the starting points for new stem and root growth. When conditions are favorable, these buds break dormancy and sprout, forming shoots and roots. This process is a form of cloning, meaning the resulting plants are genetically identical to the parent potato.
Gardeners refer to the piece of the tuber used for planting as a “seed potato,” even though it is biologically a piece of stem, not a seed in the botanical sense. Utilizing a piece of the tuber ensures the new plant receives an immediate, robust supply of stored energy. This initial energy reserve gives the developing plant a significant advantage, allowing it to establish a vigorous root system before relying solely on photosynthesis.
Preparing the Seed Pieces for Planting
Before planting, the whole potato must often be divided into smaller sections known as seed pieces to maximize the yield from a single tuber. Each piece should be roughly 1 to 2 ounces in weight and must contain at least one or two well-defined eyes. Use a clean, sharp knife to make precise cuts and minimize the potential transfer of pathogens. Larger potatoes can yield several seed pieces, while very small tubers may be planted whole if they possess multiple eyes.
After cutting, the pieces require a process called curing, or callousing, before they are introduced to the soil. This involves leaving the cut pieces exposed to open air in a warm, humid, and shaded location for one to three days. Curing allows a protective, cork-like layer to form over the cut surfaces. This layer significantly reduces the risk of rot and fungal infection, allowing the seed piece to establish roots and shoots without succumbing to decay.
Essential Steps for a Successful Harvest
Once the seed pieces have cured, they are ready for planting into the garden bed. Potatoes thrive in loose, well-drained soil that is slightly acidic, maintaining a pH between 5.0 and 6.0, which helps deter diseases like potato scab. Plant the pieces four to six inches deep, with the eye-side facing upward, and space them 10 to 15 inches apart. Ensure the soil is loose enough to allow the developing tubers to expand easily.
Consistent moisture is necessary, particularly once the plants begin to flower, as this signals the start of tuber formation. The most important technique for maximizing yield is known as hilling. Hilling involves gradually mounding soil or organic material around the developing stems as the plant grows taller. This technique provides loose medium for new tubers to form and prevents sunlight from reaching the developing potatoes.
Exposure to sunlight causes tubers to turn green and produce solanine, a mildly toxic compound that imparts a bitter taste. The first hilling typically occurs when the plant reaches six to eight inches tall. Subsequent hilling is performed every few weeks until the plant matures. The continuous addition of soil around the stems encourages the formation of more tubers along the buried portions of the stem.
Harvesting can begin after the foliage naturally yellows and dies back, typically two to three weeks after the plant has withered. This waiting period allows the potato skins to “set” or harden, which improves their storage life and handling quality. Digging too early can result in thin-skinned potatoes that are prone to bruising and quick deterioration.
Why Store-Bought Potatoes May Not Be Ideal
While it is biologically possible to grow potatoes from those purchased at a grocery store, doing so presents two significant hurdles. Commercial food production often applies chemical sprout inhibitors, such as maleic hydrazide or chlorpropham (CIPC). These chemicals extend the shelf life by preventing the eyes from sprouting prematurely, which directly inhibits the ability of the seed piece to grow once planted.
The second, more serious concern is the introduction of disease into the garden soil. Commercial potatoes are not subjected to the same rigorous inspection and certification process as dedicated “seed potatoes.” They may carry common potato pathogens like late blight, scab, or various viruses without showing obvious symptoms. Planting these non-certified tubers risks contaminating the garden bed, potentially ruining future potato crops and affecting other susceptible plants. Dedicated seed potatoes are certified to be disease-free, making them a much safer choice for gardening.