World Book Encyclopedia, 2003

Watermelon is a large, sweet fruit.  It has a smooth rind (hard outer skin) and juicy, edible flesh.  Most watermelons possess seeds, but growers also produce seedless types.  Watermelons may appear round, oval, oblong, or blocky in shape.  The rind is striped or solid and can be various shades of green or grayish-green, with the stripes darker in color.  The flesh of ripe watermelons may have white, yellow, orange, pink, or red coloring.  People often classify watermelon cultivars (varieties) by weight.  The smallest fruits weigh less than 12 pounds (5.4 kilograms).  The largest weigh more than 32 pounds (14.5 kilograms), with record weights exceeding 250 pounds (113 kilograms).

Watermelons consist of about 93 percent water.  Yet they provide a good source of vitamins A and C and of lycopene, a chemical that may help reduce the risk of cancer.  People generally eat the watermelon fruit fresh.  But they also eat the seeds, pickle the rind to make relish, and use the fruit in syrup and even cattle feed.

Watermelons grow on vines.  The plants require a long growing season, usually maturing in 75 to 100 days.  Growers plant the seeds about 4 feet (1.2 meters) apart in rows spaced about 6 to 8 feet (1.8 to 2.4 meters) from one another.  In cold weather, seeds are often planted in a greenhouse first.  They are then transplanted into fields after the danger of frost has passed.  Growers also transplant all seedless cultivars of watermelons.

Watermelon vines, or runners, can grow 40 feet (12.2 meters) long or more.  They produce slender, coiling tendrils and yellow blossoms.  The tendrils attach themselves to objects in the field.  Watermelon fruit develops from pollinated flowers.  When a watermelon ripens, the rind color becomes dull and the top of the fruit flattens slightly.  Ripe watermelons make a dull, hollow thud when thumped.

A fungal disease called Fusarium wilt is the main disease of watermelon plants.  The wilt fungus remains in the soil and may infect new plants for several years.  Growers control wilt by rotating the watermelon crop to a different field each year, or by planting cultivars resistant to the disease.  Watermelons also suffer from viruses, roundworms, insects, spider mites, and other pests.  Farmers combat these problems with chemical pesticides and with pest-resistant cultivars.

The watermelon plant probably originated in western or southern Africa.  China, which has cultivated the fruit for more than 1,000 years, ranks as the top watermelon-producing country.  Other major producers include Turkey, Iran, and the United States.

Todd Wehner

Scientific classification.  The watermelon plant belongs to the gourd family, Cucurbitaceae.  It is Citrullus lanatus.

Illustration by Kate Lloyd-Jones, Linden Artists

Watermelons are popular fruits with sweet, juicy flesh.  The fruits develop from the yellow flowers of the watermelon plant after the blossoms are pollinated.