A seed potato is a mature tuber used for vegetative propagation, not a true botanical seed. Preparing the tuber before planting is necessary to ensure the resulting plant grows vigorously and resists common soil-borne diseases. This preparation wakes the potato out of its natural dormancy, giving it a head start and accelerating the time to harvest. Proper preparation leads to a more uniform crop and a higher overall yield.
Selecting the Right Starter Potato
The initial selection of the source material is the first step in successful potato cultivation. The best choice is certified disease-free seed potatoes, which have been inspected and tested to ensure they are free from viruses and pathogens. Using certified stock prevents the introduction of long-lasting diseases into the garden soil, which can impact future plantings.
Avoid planting potatoes purchased from the grocery store, as these are often treated with chemical sprout inhibitors to extend their shelf life. These treatments, such as Chlorpropham (CIPC), prevent the tuber’s eyes from developing the sprouts needed for growth. If you must use uncertified tubers, select those that are firm, unblemished, and show no signs of rot or mold.
When choosing a specific variety, consider those known to thrive in your local climate and soil type. Varieties are categorized as first early, second early, or maincrop, which determines their growing time and ultimate size. Selecting a variety well-suited to your region ensures the best potential for a high-quality harvest.
The Chitting Process
Chitting, also known as green sprouting, encourages the potato’s eyes to develop short, sturdy sprouts before planting. This pre-germination step gives the potato plant a two to four-week advantage in the growing season. To begin chitting, place the potatoes in a single layer with the end containing the most eyes, often called the rose end, facing upward.
Shallow trays, such as egg cartons, work well for holding the tubers steady during sprouting. The ideal environment for chitting involves a cool, frost-free temperature, preferably between 50–60°F (10–15°C). Maintaining this temperature prevents the potato from shriveling while still encouraging sprout growth.
The location must provide bright, indirect light to stimulate the correct type of growth. Direct sunlight can scorch the developing sprouts. Darkness causes the sprouts to become long, white, and spindly, which are weak and easily broken. In proper light, the sprouts will develop into thick, dark green or purple buds, ready for planting when they reach about one inch in length, typically after two to four weeks.
Preparing Cut Seed Pieces
Once the potatoes have successfully chitted, larger tubers can be cut into smaller pieces to maximize the number of plants. The ideal seed piece should weigh between 1.5 to 2 ounces and must contain at least one healthy eye or sprout. Cutting the potato into blocky shapes provides more stored energy to fuel the initial growth of the new plant than thin slices.
Smaller, whole seed potatoes, roughly the size of a golf ball or a chicken egg, should be planted whole. If cutting, use a clean, sharp knife to minimize the risk of transferring disease between tubers. The best time to cut is either a few days before planting or immediately prior to placing them in the soil.
After cutting, the seed pieces require curing, which allows the cut surfaces to dry and form a protective layer. Spread the pieces in a single layer in a warm, humid environment, away from direct sun, for one to three days. This drying allows a tough, leathery callus to form over the wound. The callus acts as a barrier against soil-borne pathogens and prevents the piece from rotting once planted in cool, damp ground.