The appearance of small, green, tomato-like spheres on a potato plant often confuses home gardeners, who focus on the underground edible tubers. These objects are not miniature potatoes, but the plant’s true botanical fruit, sometimes called potato berries or seed balls. Seeing this fruit is a normal sign that the potato flower has been successfully pollinated. This indicates the plant is undergoing its natural sexual reproduction cycle.
Identifying the Potato Fruit
The potato fruit (Solanum tuberosum) is typically round, about the size of a marble or small cherry tomato, and green, sometimes turning yellow or purple. This visual similarity to tomatoes is because the potato belongs to the Solanaceae family, or nightshade family, which also includes peppers and eggplant. The fruit develops after the plant’s flowers, which vary in color by cultivar.
Inside the fruit are tiny seeds, sometimes called “true potato seed” (TPS). Fruit production is more common in regions with cooler summer temperatures, which allows the flowers to remain long enough to be pollinated and set fruit.
The Critical Safety Concern (Toxicity)
The potato fruit is toxic due to the presence of solanine, a natural defense compound. Solanine is a glycoalkaloid produced by the potato plant, primarily concentrated in the leaves, stems, and fruit, as a protective mechanism against pests. All above-ground parts of the plant contain high levels of this compound, making them unsuitable for consumption.
Ingesting solanine can lead to solanine poisoning, which presents with gastrointestinal and neurological symptoms like nausea, vomiting, diarrhea, and headaches. The potato fruit is highly concentrated with this toxin. Its sweet, berry-like appearance poses a risk, particularly to small children or pets who might mistake it for an edible berry.
Impact on Tuber Yield and Removal Advice
Removing the potato fruit relates to energy diversion within the plant. Developing flowers and fruit requires the plant to expend energy and sugars, resources also needed to bulk up the underground tubers. This competition means the plant diverts energy toward creating seeds instead of storing it in the edible tubers.
Studies suggest that fruit formation can slightly depress tuber yield. However, for a typical home gardener, the practical impact of removing the small number of fruit is often minimal on the final harvest size, as the energy cost is relatively small.
Removal is primarily recommended as a safety precaution to eliminate a toxic hazard from the garden, not for a significant yield increase. If you see the small green fruit, gently pinch or clip them off the plant to prevent accidental ingestion by children or animals. Once removed, dispose of the fruit in a manner that keeps them out of reach of pets, such as in the trash or a sealed compost bin.