The process of preparing potatoes for planting often involves cutting the whole tuber into smaller sections to maximize the number of resulting plants. These smaller pieces, known as seed potatoes, must contain at least one or two “eyes,” which are the dormant buds from which new shoots will emerge. Cutting the tuber creates an open wound, exposing the moist internal tissue to the environment and potential threats in the soil. Before a cut seed piece can be safely planted, it must undergo a natural healing process to protect the vulnerable surface and ensure the seed piece is ready to germinate successfully rather than succumbing to disease or drying out.
The Purpose and Process of Suberization
The healing of the cut surface is a biological process called suberization, which involves the formation of a protective layer. This layer acts as a defense mechanism against external threats and internal moisture loss. Within hours of the cut being made, the exposed cells begin to synthesize and deposit a waxy, hydrophobic material called suberin. This initial deposition creates a chemical seal at the wound site.
The primary function of this newly formed suberin barrier is two-fold: it prevents the rapid desiccation of the moist interior tissue, and it blocks the entry of common soil-borne pathogens. Without this protective coating, the seed piece would quickly lose water, shriveling and losing the necessary vigor to sprout. More significantly, the exposed flesh provides an easy entry point for fungal and bacterial diseases, such as soft rot and Fusarium dry rot, which can quickly destroy the seed piece before it can establish a plant.
While the initial suberin layer forms quickly, the complete healing process involves a second stage where a new layer of cells, called the wound periderm, forms beneath the suberin. This periderm is essentially a new, corky “skin” that provides long-term, robust protection against more persistent fungal threats like Fusarium. Proper curing, therefore, is not merely drying the surface but actively supporting the internal biological mechanisms that build this new, durable protective barrier.
Required Environmental Conditions for Success
To encourage the biological process of suberization, the cut seed pieces must be held in a controlled environment. Temperature and humidity both play important roles in determining the success and speed of healing. The ideal temperature range for this process is between 60 and 70 degrees Fahrenheit (15 to 21 degrees Celsius). Temperatures much lower than this slow down the metabolic rate of the cells, delaying the formation of the suberin and periderm, while excessively high temperatures can promote the rapid development of rot-causing bacteria.
Equally important is maintaining a high level of moisture in the air surrounding the seed pieces. A relative humidity of 85 to 95 percent is necessary to prevent the exposed surface from drying out too quickly before the suberin layer has a chance to form. If the air is too dry, the tissue will simply shrivel, inhibiting the cellular activity required for healing and creating a poor seal. Home gardeners can achieve this high humidity by placing the cut pieces in a humid basement or garage, or by covering them with a damp cloth or burlap sack, ensuring the material does not touch the pieces directly.
Finally, the pieces must have access to oxygen, as suberization is an aerobic process that requires air circulation. They should be spread out in a single layer or in shallow trays to prevent them from being piled too deeply, which can restrict airflow and lead to anaerobic conditions that encourage rot. Maintaining adequate ventilation also helps prevent the condensation of free water on the surface of the pieces, which would create a perfect environment for bacterial growth and completely halt the healing process.
Determining the Curing Duration
The duration required for the healing process is less about adhering to a strict timeline and more about achieving a specific physical result. The recommended period for curing cut seed potatoes is between two and four days, provided the proper temperature and humidity conditions are consistently met. Within the first 48 hours, the initial suberin layer forms, which is often enough to protect against the most immediate threat of bacterial soft rot.
However, for more complete and durable protection against aggressive fungal pathogens like Fusarium dry rot, a full five to seven days of curing may be necessary. The best way to determine if the pieces are ready for planting is to perform a visual and tactile inspection. A successfully cured seed piece will have a surface that feels dry and firm, often described as having a leathery texture or a slightly darkened, callus-like appearance.
Rushing the process and planting pieces that have not fully healed significantly increases the risk of crop failure. An uncured piece planted into cold, wet soil is highly susceptible to decay, as moisture and pathogens easily infiltrate the exposed interior. If the planting ground is not yet ready, the cured pieces can be safely held at a slightly cooler temperature (around 50°F or 10°C) until conditions are suitable.