Seed potatoes are small tubers or pieces of larger potatoes used to start a new crop. Gardeners often cut large seed potatoes into smaller sections, each containing at least one or two “eyes” or buds, to maximize the number of plants they can grow. Cutting creates fresh wounds on the potato flesh, exposing the vulnerable interior. Before planting, these cut pieces require a short, controlled preparation period known as curing, which prepares the potato piece for the challenges of the planting environment.
Why Curing Cut Seed Potatoes is Essential
Curing is a healing process that allows the cut potato surface to form a protective barrier against external threats. This natural response, known as suberization, occurs when the potato tissue produces a waxy substance called suberin, which seals the exposed flesh. This layer strengthens into a tough, cork-like covering, or callus, over the wound.
The formation of this callus serves two primary functions for the seed piece planted in the soil. First, it significantly reduces the loss of internal moisture, preventing the seed piece from desiccating before sprouts emerge. Second, the protective callus provides a physical barrier against soil-borne pathogens and decay organisms. Without this cured layer, the moist, starchy interior would be highly susceptible to fungal and bacterial rot, especially in cool or wet soil conditions.
The Ideal Conditions for Curing
Achieving successful suberization requires maintaining specific environmental conditions that stimulate the healing process. The temperature of the curing area should range between 50°F and 60°F for rapid wound healing. Warmer conditions, up to 70°F, accelerate cellular activity, but excessively high temperatures can encourage premature sprouting.
High relative humidity is also required for a robust callus, ideally maintained between 85% and 95%. This high moisture level prevents the cut surface from drying out too quickly, which would result in a thin, weak layer. High humidity encourages the formation of the thicker, leathery callus necessary for true protection.
The cut seed pieces must be placed in a single layer or shallow piles to ensure proper air circulation reaches all surfaces. Good airflow is necessary to remove carbon dioxide and maintain uniform temperatures, preventing localized heating that interferes with wound healing. The seed pieces should be kept out of direct sunlight and strong drafts to avoid desiccation and greening (the formation of the toxic compound solanine).
Determining the Curing Duration
Under ideal environmental conditions, the curing process is usually completed within two to five days. This time frame allows for the full development of the protective callus without encouraging excessive sprouting before planting. If conditions are less than optimal, or in commercial operations, the curing period may be extended up to a week or slightly longer.
The most reliable way to determine if the process is complete is by visually inspecting the cut surfaces. A properly cured seed piece will have a cut face that appears dry to the touch and has developed a firm, leathery, or cork-like texture. If the cut surface remains moist or soft, the curing process must continue.
Several factors influence the time required, most notably the temperature of the curing environment. If seed pieces are held at the cooler end of the acceptable range, the healing process slows down, necessitating a longer duration. Environmental conditions remain the greatest determinant, though the size of the seed pieces and potato variety play a minor role.
Post-Cure Handling and Storage
Once the seed pieces have developed their leathery, protective callus, they are ready for immediate planting or temporary storage. If the soil has warmed sufficiently—ideally between 50°F and 60°F—the cured pieces can be planted right away. Planting into soil at this temperature promotes rapid sprouting and ensures wound healing continues in the ground.
If planting must be delayed due to unsuitable soil conditions, the cured seed pieces require temporary storage under different conditions than those used for curing. The primary goal of temporary storage is to maintain the seed piece in a dormant state until the planting window arrives. This is accomplished by lowering the temperature to about 38°F to 40°F, which slows metabolic processes and discourages early sprouting.
High humidity, around 90% or 95%, is still maintained during temporary storage to prevent the pieces from shriveling or losing excessive moisture. The pieces should be stored in a dark, well-ventilated area, often in sacks or crates, to ensure air movement and prevent greening until they are moved for planting.