People queueing for watermelons in East Berlin, 1977. Photo by George Garrigues
Watermelon (Citrullus lanatus (Thunb.), family Cucurbitaceae) is a vine-like (scrambler and trailer) flowering plant originally from southern Africa. Its fruit, which is also called watermelon, is a special kind referred to by botanists as a pepo, a berry which has a thick rind (exocarp) and fleshy center (mesocarp and endocarp). Pepos are derived from an inferior ovary, and are characteristic of the Cucurbitaceae. The watermelon fruit, loosely considered a type of melon – although not in the genus Cucumis – has a smooth exterior rind (usually green with dark green stripes or yellow spots) and a juicy, sweet interior flesh (usually deep red to pink, but sometimes orange, yellow, or white).
Watermelon is thought to have originated in southern Africa, where it is found growing wild. It reaches maximum genetic diversity there, with sweet, bland and bitter forms. In the 19th century, Alphonse de Candolle claimed the watermelon was indigenous to tropical Africa. Though Citrullus colocynthis is often considered to be a wild ancestor of watermelon and is now found native in north and west Africa, it has been suggested on the basis of chloroplast DNA investigations that the cultivated and wild watermelon diverged independently from a common ancestor, possibly C. ecirrhosus from Namibia.
By the 10th century, watermelons were being cultivated in China, which is today the world's single largest watermelon producer. By the 13th century, Moorish invaders had introduced the fruit to Europe; according to John Mariani's Dictionary of American Food and Drink, "watermelon" made its first appearance in an English dictionary in 1615.
Watermelons were grown by Native Americans in the 16th century. Early French explorers found the fruit being cultivated in the Mississippi Valley. Many sources list the watermelon as being introduced in Massachusetts as early as 1629. Southern food historian John Egerton has said he believes African slaves helped introduce the watermelon to the United States. Texas Agricultural Extension horticulturalist Jerry Parsons lists African slaves and European colonists as having distributed watermelons to many areas of the world. Parsons also mentions the crop being farmed by Native Americans in Florida (by 1664) and the Colorado River area (by 1799). Other early watermelon sightings include the Midwestern states (1673), Connecticut (1747) and the Illiana region (1822).
Charles Fredric Andrus, a horticulturist at the USDA Vegetable Breeding Laboratory in Charleston, South Carolina, set out to produce a disease-resistant and wilt-resistant watermelon. The result, in 1954, was "that gray melon from Charleston". Its oblong shape and hard rind made it easy to stack and ship. Its adaptability meant it could be grown over a wide geographical area. It produced high yields and was resistant to the most serious watermelon diseases: anthracnose and fusarium wilt.
Today, farmers in approximately 44 states in the US grow watermelon commercially, and almost all these varieties have some 'Charleston Gray' in their lineage. Georgia, Florida, Texas, California and Arizona are the US's largest watermelon producers. This now-common watermelon is often large enough that groceries often sell half or quarter melons. Some smaller, spherical varieties of watermelon, both red- and yellow-fleshed, are sometimes called "icebox melons".
For commercial plantings, one beehive per acre (4,000 m2 per hive) is the minimum recommendation by the US Department of Agriculture for pollination of conventional, seeded varieties.
Because seedless hybrids have sterile pollen, pollinizer rows of varieties with viable pollen must also be planted. Since the supply of viable pollen is reduced and pollination is much more critical in producing the seedless variety, the recommended number of hives per acre, or pollinator density, increases to three hives per acre (1,300 m2 per hive). Watermelons have a longer growing period than other garden plants and can often take up to 85 days of growing to mature.
A watermelon contains about 6% sugar and 91% water by weight. As with many other fruits, it is a source of vitamin C.
The amino-acid citrulline was first extracted from watermelon and analyzed. Watermelons contain a significant amount of citrulline and after consumption of several kilograms, an elevated concentration is measured in the blood plasma; this could be mistaken for citrullinaemia or other urea cycle disorders.
Watermelon is mildly diuretic and contains large amounts of carotenoids. Watermelon with red flesh is a significant source of lycopene. Preliminary research indicates the consumption of watermelon may have antihypertensive effects.
The more than 1200 varieties of watermelon range in weight from less than one to more than 200 pounds; the flesh can be red, orange, yellow or white.
Watermelon with yellow flesh
Cubic watermelon from Japan
The 'Carolina Cross' produced the current world record watermelon weighing 262 pounds (119 kg). It has green skin, red flesh and commonly produces fruit between 65 and 150 pounds (29 and 68 kg). It takes about 90 days from planting to harvest.
The 'Yellow Crimson' has a yellow-colored flesh. It has been described as sweeter and more honey-flavored than the more popular red-flesh watermelon.
The 'Orangeglo' has a very sweet orange flesh, and is a large, oblong fruit weighing 9–14 kg (20–30 pounds). It has a light green rind with jagged dark green stripes. It takes about 90–100 days from planting to harvest.
The 'Moon and Stars' variety was created in 1926. The rind is purple/black and has many small, yellow circles (stars) and one or two large, yellow circles (moon). The melon weighs 9–23 kg (20–50 pounds). The flesh is pink or red and has brown seeds. The foliage is also spotted. The time from planting to harvest is about 90 days.
The 'Cream of Saskatchewan' consists of small, round fruits around 25 cm (10 inches) in diameter. It has a quite thin, light green with dark green striped rind, with sweet white flesh and black seeds. It can grow well in cool climates. It was originally brought to Saskatchewan, Canada, by Russian immigrants. The melon takes 80–85 days from planting to harvest.
The 'Melitopolski' has small, round fruits roughly 28–30 cm (11–12 inches) in diameter. It is an early ripening variety that originated from the Volga River region of Russia, an area known for cultivation of watermelons. The Melitopolski watermelons are seen piled high by vendors in Moscow in summer. This variety takes around 95 days from planting to harvest.
The 'Densuke' watermelon has round fruit up to 25 lb (11 kg). The rind is black with no stripes or spots. It is grown only on the island of Hokkaido, Japan, where up to 10,000 watermelons are produced every year. In June 2008, one of the first harvested watermelons was sold at an auction for 650,000 yen (US$ 6,300), making it the most expensive watermelon ever sold. The average selling price is generally around 25,000 yen ($ 250).
In Japan, farmers of the Zentsuji region found a way to grow cubic watermelons, by growing the fruits in glass boxes and letting them naturally assume the shape of the receptacle. The cubic shape was originally designed to make the melons easier to stack and store, but the cubic watermelons are often more than double the price of normal ones, and much of their appeal to consumers is in their novelty. Pyramid-shaped watermelons have also been developed and any polyhedral shape may potentially also be used.
The Oklahoma State Senate passed a bill on 17 April 2007 declaring watermelon as the official state vegetable, with some controversy surrounding whether a watermelon is a vegetable or a fruit.
The citrulline in watermelon (especially in the rind) is a known stimulator of nitric oxide. Nitric oxide is thought to relax and expand blood vessels, much like the erectile dysfunction drug Viagra, and may even increase libido.
Fans of the Saskatchewan Roughriders of the CFL started a tradition of hollowing out a watermelon and wearing it as a makeshift football helmet (the color of the Roughriders is green). During the 2009 Grey Cup in Calgary (between the Montreal Alouettes and the Roughriders), thousands of watermelons had to be imported to Calgary supermarkets to prevent a shortage being caused by Rider fans.
The town of Chinchilla in Queensland, Australia, holds a biannual festival celebrating all things melon.
The ten-lined June beetle is often affectionately referred to as a watermelon beetle, due to the green, striped pattern on its back.
^Wada, M. (1930). "Über Citrullin, eine neue Aminosäure im Presssaft der Wassermelone, Citrullus vulgaris Schrad". Biochem. Zeit.224: 420.
^Mandel, H.; Levy, N.; Izkovitch, S. and Korman, S. H. (2005). "Elevated plasma citrulline and arginine due to consumption of Citrullus vulgaris (watermelon)". Berichte der deutschen chemischen Gesellschaft28 (4): 467–472. doi:10.1007/s10545-005-0467-1. PMID15902549.
^Figueroa A, Sanchez-Gonzalez MA, Wong A, Arjmandi BH (2012). "Watermelon extract supplementation reduces ankle blood pressure and carotid augmentation index in obese adults with prehypertension or hypertension". American journal of hypertension25 (6): 640–3. doi:10.1038/ajh.2012.20. PMID22402472.