The watermelon is botanically classified as a pepo, a type of berry belonging to the gourd family. Native to Africa, the plant has been cultivated for thousands of years. While over a thousand specific cultivars exist globally, varieties are generally sorted into a few major commercial categories based on physical traits and intended use. Classification relies primarily on general attributes like size, shape, and the presence or absence of seeds.
Categorizing Watermelons
The most common system for distinguishing watermelons groups them primarily by their size and shape, which often determines their market niche and suitability for home gardens. The smallest category is the Icebox type, named for their convenient size that fits easily into a refrigerator. These melons typically weigh between six and fifteen pounds and are often round or slightly oval, with ‘Sugar Baby’ being a classic example known for its dark green rind and deep red flesh.
Moving up in size, the Picnic or Traditional category includes the largest watermelons, which are suitable for feeding a crowd. These melons can range from twenty to forty-five pounds and possess a thick rind, making them excellent for shipping and storage. Varieties like the oblong ‘Charleston Gray,’ which has a pale green rind, and the dark green, nearly solid-colored ‘Black Diamond’ are well-known examples of this traditional group.
A sub-group within the mid-to-large size range is often characterized by its high sugar content and distinctive striped appearance, such as the ‘Crimson Sweet’ or ‘Jubilee’ types. These varieties are highly popular due to their reliable sweetness and medium-to-large size, bridging the gap between the compact Icebox melons and the massive Picnic types.
The Seedless Variety
Seedless watermelons represent a classification based on a genetic distinction rather than just size or shape, and they now account for approximately 92% of all watermelon sales in the United States. This modern type is a triploid hybrid, meaning it possesses three sets of chromosomes (3n) instead of the standard two sets (diploid, 2n) found in seeded varieties. The uneven number of chromosomes results in sterility, preventing the development of mature, hard, black seeds.
The process begins by chemically treating a standard diploid plant to create a tetraploid parent (4n). When this tetraploid female plant is cross-pollinated with a normal diploid male plant, the resulting seed produces a sterile triploid plant that yields the seedless fruit. Although the fruit is seedless, it still requires pollination by a seeded diploid variety planted nearby to trigger fruit development.
Beyond Red: Exploring Flesh Colors
While most people associate watermelon with a deep red interior, the flesh color is another classification that introduces distinct varieties into the market. The familiar red hue comes from the carotenoid pigment lycopene, the same compound found in tomatoes and pink grapefruit. However, varieties that lack the enzyme to produce lycopene can instead accumulate other carotenoids, resulting in yellow or orange flesh.
Yellow-fleshed watermelons often contain pigments like violaxanthin and neoxanthin, giving them a bright, sunny color. The flavor profile of these yellow types, such as ‘Yellow Doll,’ is frequently described as having a unique, honey-like or tropical sweetness, sometimes with a slightly tangier note than red varieties.
Orange-fleshed melons, like ‘Orangeglo,’ are typically rich in beta-carotene, the pigment that gives carrots their color, and may have a milder, less acidic taste profile. The external appearance of these non-red melons can be highly varied, with some having a solid rind and others featuring stripes that are indistinguishable from their red counterparts.