Watermelons are a favorite summer treat, but the question of whether they have a stem is often confusing because the term refers to two different parts of the plant. A watermelon (Citrullus lanatus) is a flowering plant in the Cucurbitaceae family, which includes squash and cucumbers. Its fruit is technically a specialized berry known as a pepo, characterized by a hard rind and a fleshy interior. The short, woody piece attached to a harvested melon is often called the stem, but the plant’s true stem is the long, sprawling vine it grows on. It is important to distinguish between the primary stem and the fruit attachment point.
The Primary Stem (The Vine)
The watermelon plant’s true stem is the long, flexible vine, which trails along the ground or sprawls outward from the plant’s center. This creeping growth habit allows the plant to cover a large area to maximize sun exposure. The vine can reach lengths of over 15 feet in some varieties, acting as the primary support and distribution system.
This primary stem is thin, hairy, and often angular or grooved. The vine is marked by nodes, which are points where leaves, flowers, and lateral shoots branch off. The function of this stem is to transport water and dissolved nutrients absorbed by the shallow root system up to the leaves for photosynthesis.
The vine also produces specialized, coiled structures called tendrils at the nodes, which help anchor the sprawling plant to the ground or surrounding objects. These tendrils are modified stems that provide support as the heavy fruit develops. The transport of sugars produced in the leaves is carried out through the vine down to the developing melons.
The Fruit Stem (The Peduncle)
The part most commonly mistaken for the watermelon’s stem is the short, tough piece connecting the fruit to the vine, called the peduncle. The peduncle is not a primary stem but the stalk of the fruit itself, serving as the physical and vascular link between the growing melon and the parent vine. This structure is rich in xylem and phloem tissues, ensuring a continuous supply of water and sugars throughout development.
The peduncle is thick and woody, especially near the mature fruit, which provides the necessary structural support for the melon’s substantial weight. When the fruit is young, the peduncle is green and succulent, matching the vine’s color. As the melon matures, the peduncle often begins to harden and become more brittle.
The point where the peduncle meets the main vine is a specialized area known as the abscission zone. In many fruits, this zone weakens naturally when the fruit is ripe, causing the fruit to detach cleanly. However, in watermelons, this zone does not typically allow for a clean break, which is why the peduncle usually remains firmly attached to the melon even after harvest.
Stem Appearance and Harvesting
The appearance of the peduncle and the nearest tendril are used by growers as indicators of ripeness, since the watermelon fruit does not continue to ripen after picking. The curly tendril located opposite the fruit’s attachment point is a useful visual cue. While this tendril is green and fresh during development, it will begin to dry out and turn brown once the fruit has reached full maturity.
Observing this tendril, sometimes called the “pig’s tail,” provides a reliable sign that the flow of nutrients to the fruit is complete and the melon is ready for harvest. A completely dry and shriveled tendril, along with a dulling of the fruit’s rind, signals optimal ripeness. Conversely, a green, vibrant tendril means the fruit is still actively drawing sustenance from the vine and is not yet sweet.
When harvesting a ripe watermelon, the peduncle is cut with a knife or shears rather than being pulled off. It is standard practice to leave a small section of the peduncle, typically two to four inches, attached to the harvested melon. This short piece of woody stem acts as a natural seal, slowing moisture loss and preventing the entry of decay-causing pathogens, which extends the melon’s shelf life.