Yes, potatoes have leaves, which form the green, bushy foliage seen above ground. The potato plant, Solanum tuberosum, is an herbaceous perennial in the nightshade family, Solanaceae, making it a relative of tomatoes and eggplants. Although the part of the plant we eat is a starchy, underground tuber, the entire plant relies on above-ground growth, including the visible leaves and stems, collectively known as the canopy.
Understanding Potato Plant Anatomy
The potato plant is divided into parts that serve different functions, both above and below the soil surface. The foliage, which consists of the leaves and the main stems, grows upward, sometimes reaching a height of up to 40 inches. Potato leaves are compound, meaning each leaf is composed of several smaller leaflets arranged along a central stalk.
The stems of the potato plant are often referred to as haulms, providing structural support for the leaves. Growing from the base of the haulms, just below the soil line, are specialized underground stems called stolons. The edible potato itself is not a root, but rather a stem tuber, which forms when the tips of these stolons swell and enlarge to store nutrients.
The botanical classification of the potato tuber as a modified stem is confirmed by the presence of “eyes,” which are dormant buds or nodes. These buds are a characteristic feature of stems and allow a potato to sprout and grow a new plant when planted. In contrast, true root vegetables lack these nodes and have a different internal structure.
The Essential Role of Potato Leaves
The leaves of the potato plant are necessary for the formation and development of the edible tubers. Their primary function is to capture sunlight and perform photosynthesis, the process that converts light energy into chemical energy in the form of sugars. This process is facilitated by chlorophyll, the pigment that gives the leaves their green color.
These sugars, or photoassimilates, are then transported from the leaves down through the plant’s vascular system to the underground stolons. The plant directs this stored energy to the tips of the stolons, causing them to swell and become the starchy tubers. The size and health of the leafy canopy directly determine the potential yield and size of the potato crop.
The leaves act as the plant’s food factory, continuously fueling the growth of the tubers throughout the growing season. As the plant approaches the end of its life cycle, the leaves and stems begin to die back, a natural process known as senescence. This process signals the maturation of the tubers below ground.
Safety Concerns Regarding Potato Foliage
While the leaves are functionally important, the above-ground parts of the potato plant are toxic and should never be consumed. Like other members of the nightshade family, potato leaves and stems contain high levels of compounds called glycoalkaloids, primarily solanine and chaconine. These compounds are produced by the plant as a natural defense mechanism to deter pests and herbivores.
The concentration of these toxins in the leaves and stems can be up to 1,000 times higher than the minimal amounts found in a properly stored tuber. Ingesting the foliage can cause gastrointestinal distress and neurological symptoms in humans and livestock. Glycoalkaloids are also heat-stable, meaning cooking does not significantly reduce their toxicity.
Even the edible tuber can develop higher levels of solanine if it is exposed to light, which is why potatoes turn green when left uncovered. The green color is chlorophyll, but its presence indicates that the toxic glycoalkaloids have also increased as a protective response. This is why it is advised to remove any green portions from a potato before eating it.