Potatoes are a staple crop, and preparing seed potatoes—tubers grown specifically for planting—is a routine step for gardeners and farmers. Preparation often involves deciding whether to cut the tubers into smaller pieces. This practice is not always necessary, as smaller seed potatoes can be planted whole. The decision to cut depends entirely on the tuber’s size and the goal of propagating more plants from the available stock.
When and Why Seed Potatoes Should Be Cut
The decision to cut seed potatoes is driven by economics and the goal of maximizing yield from each tuber. Larger seed potatoes contain multiple growth points, known as “eyes.” Cutting them allows a single potato to be divided into several viable planting pieces, which effectively stretches the initial investment and produces a greater overall harvest.
A successful planting piece must contain at least one, and preferably two, healthy eyes—the buds that sprout to form the new plant. The piece must also be large enough to fuel initial growth until the plant establishes its root system. Seed potatoes weighing between 1.5 and 3 ounces should be planted whole for the best start. Only tubers exceeding this size, such as those in the five-to-seven-ounce range, are candidates for cutting into two or three separate pieces, as they possess enough stored energy to support multiple plant starts.
Proper Cutting Technique
Cutting must be executed with precision to ensure each resulting piece is a robust start for a new plant. Each seed piece should be cut into a blocky shape, ideally weighing between 1.5 to 2.0 ounces. This chunky size provides the necessary reservoir of stored starch to support sprout and root development before the plant begins photosynthesis.
Thin slivers or flat pieces should be discarded, as they lack the mass required for vigorous early emergence and growth. Before cutting, warm the seed potatoes to between 45 and 50 degrees Fahrenheit; this makes the tissue easier to cut cleanly and promotes faster healing. Sanitation is also necessary to prevent the spread of soil-borne diseases. The cutting tool should be disinfected before starting and periodically throughout the process, often by dipping it in a bleach or alcohol solution. The goal is to create the largest possible seed piece with the fewest cut surfaces, which reduces the area vulnerable to decay organisms in the soil.
Curing Cut Pieces Before Planting
After cutting, the fresh surfaces are highly vulnerable, making the next step, known as curing or suberization, necessary for success. Curing is the biological process where the potato forms a protective, cork-like layer, called a periderm or callus, over the exposed flesh. This process seals the wound, preventing the seed piece from rapidly losing moisture and protecting it from pathogens and rot-causing organisms.
Optimal curing conditions involve placing the cut pieces in an environment with high humidity (ideally 85 to 95 percent) and moderate temperatures (around 50 to 60 degrees Fahrenheit) for two to three days. Good air circulation is beneficial during this time to prevent carbon dioxide buildup and ensure even drying. Without this protective callus layer, a seed piece planted in cool, moist soil is susceptible to fungal and bacterial infections that cause it to rot before the sprout emerges. Cured pieces should have a tough, leathery texture on the cut sides, indicating they are ready to be planted.