The potato plant (Solanum tuberosum) is a member of the nightshade family, Solanaceae, alongside tomatoes and peppers. Unlike many common garden vegetables, the potato is cultivated for its underground structure rather than its fruit or leaves. This description focuses on the plant’s physical makeup, from its green canopy to its hidden storage organs.
Above-Ground Appearance: Stems and Foliage
The visible portion of the potato plant generally forms a bushy, sprawling, or erect habit, typically reaching a height between one and three feet. Multiple stems, or shoots, emerge from the soil, giving the plant a full appearance. These stems are often angular and can be green, though some varieties display purplish or reddish pigmentation, especially near the base. The stems may be smooth or covered in fine, sparse hairs.
The foliage consists of large, compound leaves arranged alternately along the stem. Each leaf is composed of several smaller leaflets, a structure known as pinnately compound. A single leaf often contains six to eight pairs of leaflets, which vary irregularly in size, giving the overall leaf a jagged or uneven look.
Individual leaflets are generally oval to heart-shaped with pointed tips and exhibit a rich, dark green color. The surface texture is often slightly hairy or matte, which helps the plant reduce water loss. As the plant approaches maturity, its leaves and stems naturally begin to yellow and die back, signaling that the plant is directing energy toward the underground structures.
Flowers and True Fruit Identification
During the growing season, the potato plant may produce small, star-shaped flowers that bloom in clusters called cymes. These flowers feature five fused petals surrounding prominent yellow central stamens. Flower color is variable across cultivars, commonly appearing as white, pink, purple, or blue.
If successfully pollinated, the plant may develop a small, round fruit often referred to as a “potato berry.” This true fruit appears green or yellowish-green and resembles a tiny, oblong cherry tomato, usually measuring about half an inch in diameter. Each berry can contain up to 300 seeds, which are used for breeding new varieties.
All parts of the potato plant growing above the ground, including the stems, leaves, flowers, and berries, contain toxic compounds called glycoalkaloids, such as solanine. The small, tomato-like berries are particularly toxic and should not be consumed. While the presence of these fruits is a natural part of the plant’s reproductive cycle, most commercially grown potatoes are propagated using the underground tubers.
The Hidden Growth: Tubers and Roots
The underground architecture of the potato plant consists of two distinct structures: a true root system and the specialized tubers. The true roots are fibrous and relatively shallow, primarily functioning to absorb water and nutrients from the upper soil layers. This root system typically does not extend much deeper than two feet into the soil.
The edible potato, the tuber, is not a root but a modified stem. It develops from specialized underground stems called stolons, which grow horizontally from the base of the plant’s main stem. The ends of these stolons swell up as the plant produces and stores excess carbohydrates in the form of starch.
The tuber’s surface features small indentations known as “eyes,” which are vegetative buds from which new shoots can sprout. Tubers vary widely in size, shape, and skin color depending on the variety. They function as the plant’s primary energy storage and reproductive organ. The number of mature tubers can range from five to fifteen per plant, depending on environmental factors like moisture and nutrients.