Kennebec potatoes are a medium-to-late maturing variety, recognized for their excellent culinary qualities and adaptability for chipping and frying. They possess a naturally good storage life, but achieving maximum yield and extending this potential depends on precise harvest timing and proper post-harvest handling.
Timing Indicators: New Potatoes Versus Storage Potatoes
The correct moment to harvest Kennebec potatoes is determined by the desired culinary outcome: either tender new potatoes for immediate eating or fully matured tubers for long-term storage. New potatoes are typically ready for harvest between 60 and 70 days after planting. This stage is often visually signaled by the appearance of flowers on the plant’s foliage.
At this early point, the tubers are smaller, and their delicate skins are thin and easily rubbed off, which is why they must be consumed quickly. In contrast, harvesting Kennebecs for storage requires waiting until they are fully mature, which occurs roughly 90 to 110 days after planting. The definitive visual cue for a storage harvest is the complete yellowing and collapse of the potato vine, a natural process called senescence. This late harvest ensures the tubers have reached their maximum size and have started the process of thickening their protective outer layer.
Preparing for Storage: The Importance of Vine Dieback
The visual death of the foliage is only the first step for storage-bound Kennebecs; a preparatory period in the soil is necessary before digging. Once the vines have naturally died back or have been manually cut, a waiting period of 10 to 14 days must follow. This time is not for growth, but for a physiological process known as suberization, where the potato forms a protective waxy layer.
This waiting period allows the thin, immature skin to “set” and toughen, making it resistant to the scrapes, cuts, and bruises that occur during harvest. A properly set skin is the primary defense against moisture loss and the entry of rot-causing pathogens during storage. Without this step, the potatoes will be highly susceptible to damage and will spoil much sooner.
Harvesting Techniques and Tools
The act of removing the mature Kennebecs from the soil must be approached with care to avoid compromising the skin’s newly developed toughness. Use a specialized potato fork or a pitchfork, which has rounded tines, rather than a sharp shovel. A pitchfork minimizes the risk of puncturing the tubers, which creates a wound vulnerable to decay.
Begin digging a wide perimeter, at least 12 inches away from where the main stem emerges, and then gently lift the soil and the cluster of potatoes. Harvesting on a warm, dry day is beneficial because dry soil is less likely to cling to the tubers and cause skin abrasions during the lifting process. If the soil is too cold, below 45°F, tubers are also more susceptible to bruising, so time the digging during the warmer part of a fall day.
Post-Harvest Handling and Storage
After removing the tubers from the ground, gently brush off the clinging soil; do not wash the potatoes, as added moisture can encourage rot. Any tubers that were accidentally cut or bruised during the digging process should be set aside for immediate use, as they will not store well and could contaminate the rest of the harvest.
The remaining healthy potatoes must then undergo a curing process for long-term storage, which involves placing them in a dark, humid, and well-ventilated area for 10 to 14 days. This environment, ideally maintained at 50 to 60°F with high humidity, allows any minor surface wounds to heal completely.
Following this curing period, the Kennebecs should be moved to their final storage location: a dark space with a temperature range of 35 to 40°F and a high relative humidity of about 90 percent. Storing them in darkness prevents the development of greening, which indicates the presence of solanine, a toxic compound.