Seed potatoes are tubers specifically grown and certified to be disease-free for planting. Cutting these potatoes before planting is a common technique that allows a single tuber to be divided into multiple pieces, significantly increasing the number of plants you can grow and maximizing potential yield.
Preparing Seed Potatoes for Cutting
Warming tubers (60 to 70°F) for a few days stimulates the dormant growth buds, or “eyes,” preparing them for cutting. If the potatoes have developed short, stocky sprouts through chitting, they are physiologically ready for planting. It is best to cut the seed potatoes only one to three days before the actual planting date for home gardens.
Before cutting, sanitize all tools and surfaces to prevent disease spread. Use a sharp knife or blade dipped in a sanitizing solution, such as diluted bleach, between each potato. This minimizes the risk of transferring pathogens. Tubers that are damaged, soft, or showing signs of rot should be discarded.
Step-by-Step Cutting Technique
The primary goal of the cutting technique is to produce blocky pieces, each containing enough stored energy to sustain the initial growth of the new plant. Each resulting seed piece should weigh approximately 1.5 to 2 ounces, the ideal size for robust development. The piece must contain at least one healthy eye, though aiming for two to three strong, visible eyes offers greater certainty of successful sprouting.
When handling larger seed potatoes, you should first identify the end of the tuber known as the rose end, where the majority of the eyes are concentrated. The cutting should proceed in a way that distributes these growth buds as evenly as possible among the newly cut sections. It is often helpful to cut the potato lengthwise through the rose end clusters to ensure a uniform distribution of eyes on all pieces. Maintaining a blocky shape is important because the piece’s mass provides the necessary nourishment for the emerging sprout until the new roots can establish themselves.
For smaller tubers that weigh between 1.5 and 3 ounces, it is often best to plant them whole if they have sufficient eyes. Conversely, very large potatoes, those over 7 ounces, can be cut into three or four pieces, as long as the 1.5 to 2-ounce size and eye count requirements are met for each section. If a cut piece lacks sufficient flesh, the sprout may struggle to grow vigorously and could result in a weaker plant.
Curing the Cut Pieces Before Planting
After the seed potatoes have been cut, the next necessary step is to allow the pieces to cure, also known as callusing. Curing is a biological process where the freshly cut surface dries out and forms a protective, scab-like layer, or periderm. This layer seals the open wound, which is a defense mechanism the potato uses to guard against infection.
The purpose of this callusing is twofold: it prevents the entry of soil-borne pathogens and minimizes moisture loss from the cut pieces once they are planted. Without a healed surface, the exposed flesh is vulnerable to rot, especially if the spring soil is cold and wet. To facilitate proper curing, the cut pieces should be spread out in a single layer.
An ideal curing environment is a space that provides cool temperatures (60 to 65°F) combined with high humidity (85 to 95 percent). The area should also be dark or shielded from direct sunlight to prevent excessive dehydration. Allowing the pieces to cure under these conditions for two to three days is usually sufficient to form a tough, protective layer before planting.