Preparing seed potatoes before planting significantly impacts the health and yield of the resulting crop. This process, often called “curing,” is the biological response where cut surfaces heal themselves. The goal is to encourage the formation of a protective layer, or callus, over any exposed flesh. This layer acts as a natural barrier, protecting the seed piece from soil-borne diseases and preventing moisture loss after planting. Proper preparation ensures the plant’s energy is directed toward growth rather than fighting infection or desiccation.
Preparing Seed Pieces for Curing
The process begins by examining the seed tubers to determine which ones need dividing. Whole potatoes smaller than 1.5 ounces (or a golf ball) can be planted whole. Larger tubers must be cut into pieces between 1.5 and 2.5 ounces to maximize planting efficiency and yield. This weight provides sufficient stored energy for strong initial growth.
Each resulting seed piece must contain at least one healthy “eye,” the bud from which the new plant sprouts. Cutting the potato into blocky shapes is preferable to thin slices, as blockier pieces are less susceptible to rot and dehydration. Use a sharp, clean knife for cutting to minimize tissue damage and reduce the chance of introducing pathogens. The seed pieces should not be planted immediately, but moved to an environment that promotes healing.
Establishing the Callusing Environment
Callusing, or suberization, is the wound-healing mechanism that creates the protective layer over the cut surfaces. This process is accelerated by providing precise environmental conditions for a short period. The ideal temperature range to promote rapid healing is warm, around 60–70°F (15–21°C). Temperatures below this range significantly slow the formation of the protective layer.
High relative humidity, ideally 85% to 95%, is necessary to prevent the exposed tissue from drying out too quickly. This moist air allows potato cells to deposit suberin (a waxy polymer) and lignin (a woody polymer) over the wound. The healing process usually takes two to four days, resulting in a surface that looks dry, firm, and slightly leathery. Proper air circulation is also important to prevent carbon dioxide buildup, which can interfere with the healing response.
Accelerating Growth Through Chitting
“Chitting,” also known as pre-sprouting, is a beneficial step performed after the seed pieces have cured. This process involves exposing the seed potatoes to conditions that encourage the formation of short, robust sprouts. The primary benefit of chitting is that it shortens the time until harvest and leads to stronger initial growth.
To chit potatoes, the cured pieces are arranged eye-side up in a single layer. They require indirect light and a cooler temperature than the curing environment, ideally 45–55°F (7–12°C). This combination prevents the formation of long, pale, brittle sprouts, instead encouraging short, sturdy, deep-green or purple sprouts. Chitting typically takes four to six weeks, and the seed pieces are ready for planting once the sprouts reach a half-inch to one inch in length.
Handling and Planting Cured Potatoes
Once cured and potentially chitted, the seed pieces must be handled with care. The newly formed callus is delicate, and the short, thick sprouts can be easily broken off. Gentle handling minimizes the risk of damaging the sprouts and ensures the protective callus remains intact.
The prepared seed pieces should be planted into soil that is adequately warm and not overly saturated with water. Soil temperatures between 50°F and 60°F are ideal for promoting immediate growth and minimizing the risk of decay. The seed pieces are typically planted several inches deep, with the sprouts pointing upward if chitted. Planting the prepared seed pieces quickly maximizes the benefit of the preparation, allowing the plant to transition into active growth.