Potato sprouting is a natural process that signals the end of a tuber’s dormant phase, preparing it to grow a new plant. For the home gardener, this process is intentionally managed, a technique known as chitting or pre-sprouting, to maximize harvest efficiency. Chitting involves awakening the potato’s “eyes” to produce strong, healthy shoots before they are placed in the soil. This deliberate action contrasts with spontaneous sprouting in kitchen storage, which has different implications for food safety.
Why Gardeners Pre-Sprout Potatoes
The primary motivation for gardeners to pre-sprout potatoes is to gain a significant advantage in the growing season. Potatoes planted without chitting must first break dormancy and develop sprouts underground, which can take several weeks. By starting this process indoors, the potato is ready to establish roots and foliage immediately upon planting.
This head start translates directly to an earlier harvest, often by ten days to two weeks. The practice is particularly beneficial for growing early and second-early varieties, which mature quickly. In regions with short growing seasons, chitting ensures the plants have sufficient time to develop tubers before summer heat or early fall frost arrives. This initial growth boost can also contribute to a higher overall yield by optimizing the plant’s productive time in the soil.
The Process of Creating Healthy Sprouts
The process begins with selecting certified seed potatoes rather than common grocery store tubers, which are often treated with sprout-inhibiting chemicals. Large seed potatoes should be cut into pieces roughly the size of a golf ball, ensuring each section contains at least two healthy “eyes.” These cut pieces should be left exposed to the air for one to two days to allow the cut surface to dry and form a protective, cork-like layer, known as callusing, which helps prevent rot after planting.
To initiate chitting, the prepared tubers are arranged in a shallow container, such as an egg carton or a seed tray, with the end containing the most eyes facing upward. They require a specific environment to encourage the right kind of growth. The ideal location is a cool, bright, and frost-free area, such as a sunroom or garage, where temperatures consistently remain between 7 and 12 degrees Celsius (45–54 degrees Fahrenheit).
The light exposure must be indirect and diffused, not direct sunlight, which can cause the skin to green. This combination of cool temperatures and bright, indirect light is necessary for developing short, sturdy, and dark-pigmented sprouts. Long, pale, and brittle sprouts indicate the environment is too warm or too dark, causing the potato to stretch in search of light. The chitting process typically takes four to six weeks, after which the sprouts reach the optimal size for planting.
Transitioning Sprouts to the Garden
Once the sprouts, or “chits,” have developed to a robust length of approximately 25 millimeters (one inch), the seed potatoes are ready to be moved outdoors. This transition should be timed so that the risk of a hard frost has passed, and the soil temperature has warmed to at least 7 degrees Celsius (45 degrees Fahrenheit). Planting into cold, wet soil can cause the seed potato to rot before it establishes roots.
The sprouted tubers are generally planted in a prepared trench or individual holes about 10 to 15 centimeters (four to six inches) deep. Handle the seed potatoes with care during planting to avoid snapping off the newly formed sprouts. Each potato should be situated with the sprouts pointing upward to ensure the quickest emergence of foliage above ground. After placement, the tubers are covered with only a few inches of soil initially, allowing for subsequent mounding of soil, known as “earthing up,” as the plant grows.
Food Safety and Potato Storage
While intentional sprouting is beneficial for gardening, unexpected sprouting in the pantry raises concerns about edibility. When potatoes are exposed to light or stored for extended periods, they naturally produce defense compounds called glycoalkaloids, primarily solanine and chaconine. The concentration of these compounds increases significantly in the sprouts and in green areas on the potato skin.
The green color itself is chlorophyll, which is harmless, but its presence serves as a visual indicator that toxic glycoalkaloid levels are also elevated. Consuming potatoes with high concentrations of these compounds can cause gastrointestinal distress, including vomiting and abdominal pain. If a potato has only small sprouts or a little greening, these parts can be cut away before consumption, as the toxins are concentrated near the surface.
However, any potato that is heavily sprouted, excessively green, or soft and shriveled should be discarded entirely. To inhibit unwanted sprouting and maintain safety, potatoes should be stored in a cool, dark, and dry environment, ideally between 7 and 10 degrees Celsius (45–50 degrees Fahrenheit). Storing them in a breathable container, like a paper bag or a basket, and keeping them away from ethylene-releasing produce, such as onions and apples, helps to prolong dormancy.