Potatoes do not grow on vines; the edible part of the plant is an underground tuber. The confusion often arises because the above-ground portion of the plant is a bushy, sprawling collection of stems and leaves that can appear somewhat vine-like. The potato, scientifically known as Solanum tuberosum, is a member of the nightshade family, Solanaceae, which also includes tomatoes and eggplants.
Above-Ground Growth: The Potato Plant’s Foliage
The visible part of the potato plant is a mass of compound leaves and thick stems that can grow up to three feet high. This green canopy captures sunlight to fuel growth through photosynthesis. The stems are generally weak and tend to sprawl outward, contributing to the mistaken impression that the plant is a vine. Growers manage this sprawling growth by periodically “hilling up” the soil around the base to encourage proper underground development.
Potato plants produce flowers, typically appearing in shades of white, pink, purple, or blue with a yellow center. Following pollination, the plant may develop small, round, green fruits that resemble tiny tomatoes. These fruits are toxic and inedible because they contain high concentrations of glycoalkaloids, a protective chemical common in the nightshade family. The foliage itself should also not be eaten for the same reason.
Below-Ground Growth: Tuber Formation
The edible potato is not a root vegetable like a carrot or beet; botanically, it is a stem tuber, which is a specialized, thickened underground stem. The development of this tuber begins with specialized lateral stems called stolons that grow horizontally away from the main stem, just beneath the soil surface. These stolons are distinct from the true fibrous roots, which only function to absorb water and nutrients.
The process of tuber formation, or tuberization, occurs when the tips of these underground stolons begin to swell and accumulate starch. This swelling is a result of cell division and enlargement, which transforms the stolon tip into the storage organ we recognize as the potato. The “eyes” visible on the surface of a potato are actually nodes on the stem, which contain vegetative buds capable of sprouting new plants.
The conditions for tuberization are often triggered by shorter day lengths and cooler temperatures, signaling the plant to store energy for the next season. This energy storage mechanism explains why the potato is classified as a stem: it possesses features like nodes (the eyes) and internodes. During this phase, the plant’s energy is redirected from producing foliage to bulking up the tubers.
Clarifying Potato Relatives and Look-Alikes
Much of the confusion about potatoes growing on vines stems from their botanical relatives and common misidentification with other root crops. The sweet potato (Ipomoea batatas), for example, is often mistaken for a close relative but belongs to the morning glory family, Convolvulaceae. Sweet potatoes are true root vegetables; their edible part is a tuberous root, which develops from the true roots, not from underground stems.
The sweet potato plant also grows on extensive, sprawling vines above ground that can spread several feet across a garden. This vine-like habit makes the sweet potato the likely source of the “potato vine” misconception, contrasting sharply with the potato’s bushy, self-supporting stems.
Tomatoes, which share the Solanaceae family with the potato, are often grown on sprawling stems that require staking, sometimes described as vine-like. Despite this kinship, the potato’s edible part develops underground from a stem, while the tomato’s edible part is the fruit formed above ground. These distinct growth habits confirm that the true potato plant, Solanum tuberosum, does not produce its main crop on vines.