Finding a potato intended for planting that has begun to decay is common for gardeners. This raises the question of whether this compromised material can still be planted. While the initial impulse may be to salvage the tuber, this practice introduces significant, long-term risks to the current season’s harvest and the health of the garden soil. Understanding the dangers associated with planting decaying tubers is necessary for successfully growing potatoes.
Why Decaying Potatoes Should Not Be Planted
Planting a decaying potato introduces harmful pathogens directly into the garden soil, creating a reservoir of disease that can affect future plantings for years. The soft, mushy texture of a rotten tuber indicates the presence of bacteria or fungi actively breaking down the plant tissue. These microorganisms, which cause common potato diseases, can quickly spread from the planted piece to the surrounding soil and eventually infect healthy, developing tubers.
Late blight, caused by the oomycete Phytophthera infestans, is a severe threat known to survive the winter in infected tubers left in the soil. Planting a tuber compromised by bacterial soft rot or blackleg introduces Pectobacterium or Dickeya species, which thrive in moist soil and cause the mother tuber to rot rapidly. This decay prevents the establishment of a healthy plant and allows the bacteria to infect nearby healthy seed pieces or contaminate the planting area.
Fungal infections like Fusarium dry rot are transmitted through infected seed pieces, reducing crop establishment by killing developing potato sprouts. The decaying tuber lacks the stored energy needed to support vigorous growth and is unable to generate a strong, healthy plant, often resulting in poor stands or stunted emergence. Furthermore, the presence of mushy, decomposing organic matter underground can attract pests, such as rodents and various fly species, which can damage developing plants and spread disease.
Telling Rot Apart from Healthy Sprouts
Gardeners often confuse a naturally sprouting tuber with one that is irreversibly decaying. Healthy sprouting, or “chitting,” is a natural process where the potato develops short, thick, purplish or green shoots from its “eyes” when exposed to light and moderate temperatures. A healthy seed potato remains firm to the touch with smooth skin, indicating that the tuber’s internal structure is intact and its energy stores are ready to support new growth.
In contrast, a rotten potato exhibits distinct signs of tissue breakdown signaling the presence of disease. The texture will be noticeably soft, squishy, or shriveled, yielding easily when light pressure is applied. Decay is often accompanied by a foul, sulfuric odor and the appearance of wet, slimy spots or patches of mold on the surface. These physical changes indicate that the tuber is being consumed by pathogens and is losing its structural integrity and viability as seed material.
The difference lies in the tuber’s firmness and overall smell. Healthy sprouts do not compromise the tuber’s structure or emit an unpleasant odor. If the tuber is firm, the sprouts indicate readiness for planting. If the tuber is soft or mushy, the breakdown is a sign of infection, and the material should be discarded to protect the garden environment.
Selecting and Preparing Healthy Seed Potatoes
The best practice for a successful potato harvest begins with sourcing planting material from reliable vendors. Gardeners should select certified seed potatoes, which have undergone testing to guarantee they are free from common diseases such as viruses, bacterial soft rot, and fungal pathogens. Using grocery store tubers, which are generally not certified and may be treated with sprout inhibitors, introduces a risk of poor performance or disease transmission.
Larger, firm tubers can be prepared by cutting them into blocky pieces. Ensure each piece weighs between one and a half to two ounces and contains at least one or two “eyes.” After cutting, the pieces must be cured for three to five days in a warm, moderately humid area out of direct sunlight. This curing process allows the cut surface to form a protective layer, or periderm, which prevents moisture loss and acts as a barrier against soil-borne pathogens.
Before planting, chitting can be encouraged by placing the seed pieces in a bright, cool, and frost-free location to develop sturdy, thick sprouts. When planting, choose a site with loose, well-drained soil, as planting in cold or water-logged conditions increases the risk of rot, even with healthy seed. These preparation steps maximize the tuber’s ability to establish a strong root system and produce an abundant crop.