Potatoes are widely grown globally, and a frequent question is whether they reappear in the same spot the following year. The answer is a qualified affirmation rooted in the plant’s unique biology. While potatoes are typically cultivated as a single-season crop, the underground storage organs often survive the winter. Any unharvested potato tuber remaining in the soil can sprout and produce a new plant in the subsequent growing season. This unintentional regrowth occurs because the commercial growing cycle interrupts the plant’s natural life cycle.
Defining the Potato Life Cycle
The potato (Solanum tuberosum) is fundamentally a herbaceous perennial plant. In its native habitat, the plant naturally lives for more than two years, using its underground tubers for long-term survival. However, modern agriculture almost universally treats the potato as an annual plant. This means the entire plant, including the above-ground stem and foliage, is harvested within a single year.
The part of the plant that persists is the tuber, a modified, swollen underground stem. This tuber functions as a nutrient reservoir and a means of vegetative reproduction, allowing the plant to survive harsh conditions. The delicate above-ground growth dies back completely in temperate climates due to frost. The subterranean tuber remains insulated by the soil, bypassing the cold season and resuming growth when temperatures rise again.
The Mechanism of Volunteer Potatoes
The phenomenon of potatoes growing back unbidden, known as “volunteer potatoes,” depends entirely on the survival and subsequent sprouting of missed tubers. After harvest, a potato tuber enters a period of dormancy where visible bud growth is inhibited, even if conditions are favorable. This dormancy is regulated by plant hormones, particularly abscisic acid (ABA), which suppresses sprouting, and gibberellins and cytokinins, which promote it.
The eyes visible on the tuber surface are specialized buds from which new shoots emerge. To break dormancy and sprout, the tuber must be exposed to an extended period of cold temperatures, typically above the lethal threshold of around \(-2^\circ \text{C}\) (28\(^\circ \text{F}\)). Soil acts as an insulator, protecting tubers from deep freezing, especially if they are buried deeply or covered by residue. Once the soil temperature rises in the spring, dormant buds activate. Stored starch provides the energy for the new shoot to grow toward the soil surface, resulting in a volunteer plant.
Practical Concerns of Unintentional Regrowth
While a few volunteer potato plants might seem harmless, their presence poses significant practical issues for agriculture. The most serious concern is their capacity to act as a disease reservoir, undermining the benefits of crop rotation. Volunteers can harbor pathogens such as the oomycete responsible for late blight or various persistent potato viruses. Since these plants emerge from infected tubers, they provide a bridge for the disease to survive the winter and infect the newly planted commercial crop.
Volunteer potatoes are highly competitive weeds that aggressively vie for water, nutrients, and sunlight with the rotation crop. Studies document substantial yield losses in subsequent crops, reducing yields in corn by 23 to 62 percent and in sensitive crops like onions and carrots by up to 90 percent. They also contaminate the harvest of rotation crops, as potato leaves and berries mixed into a harvested pea or bean crop can lead to the rejection of the entire lot. Furthermore, volunteers complicate the management of specific varieties and can lead to a mixed, lower-quality harvest.
Proper Post-Harvest Management
Minimizing the risk of volunteer potatoes requires careful soil management immediately after harvest. The most straightforward strategy is meticulous harvesting, or gleaning, to remove as many small, unmarketable tubers as possible. Even small cull potatoes can survive and generate a new plant.
Once the main harvest is complete, soil management should focus on exposing remaining tubers to the elements. Shallow tillage in the fall brings missed tubers closer to the surface, where winter frosts (below \(-2^\circ \text{C}\)) are more likely to kill them. Deep tilling is counterproductive because it buries tubers deeper, insulating them against the cold. Implementing a strict crop rotation schedule is also necessary, ensuring the field is not planted with potatoes again for several years.