The watermelon (Citrullus lanatus) is a species of flowering plant in the family Cucurbitaceae. It is a scrambling and trailing vine-like plant cultivated worldwide.
Watermelons are grown in tropical to temperate regions for its large edible berry having a firm rind and no internal divisions; botanically, it is a pepo. The sweet, juicy flesh is usually deep red to pink, with many seeds that are black when mature and white when immature. Seedless varieties exist. The fruit can be eaten raw or pickled, and the rind is edible after cooking. It may also be consumed as a juice or an ingredient in mixed beverages.
The modern watermelon originated in Sudan where it was first domesticated and cultivated. Kordofan melons are the closest relatives and may be progenitors of modern, cultivated watermelons. Wild watermelon seeds were found in Uan Muhuggiag, a prehistoric site in Libya that dates to approximately 3500 BC. Watermelons were domesticated in Sudan and cultivated in Egypt by 2000 BC. Hebrew texts from early in the Christian era place watermelon with other sweet table fruits, and dessert watermelons spread across the Mediterranean world during Roman antiquity.
Considerable breeding effort has developed disease-resistant varieties. Many cultivars are available that produce mature fruit within 100 days of planting. In 2024, China produced 60% of the world's watermelons.
Description
The watermelon is an annual that has a prostrate or climbing habit. Stems are up to long and new growth has yellow or brown hairs. Leaves are long and wide. These usually have three lobes that are lobed or doubly lobed. Young growth is densely woolly with yellowish-brown hairs which disappear as the plant ages. Like all but one species in the genus Citrullus, watermelon has branching tendrils. Plants have unisexual male or female flowers that are white or yellow and borne on hairy stalks. Each flower grows singly in the leaf axils, and the species' sexual system, with male and female flowers produced on each plant, is monoecious. The male flowers predominate at the beginning of the season; the female flowers, which develop later, have inferior ovaries. The styles are united into a single column.
The large fruit is a kind of modified berry called a pepo with a thick rind and fleshy center (mesocarp and endocarp). Wild plants have fruits up to in diameter, while cultivated varieties may exceed . The rind of the fruit is mid- to dark green and usually mottled or striped, and the flesh, containing numerous seeds spread throughout the inside, can be red or pink (most commonly), orange, yellow, green or white.
A bitter watermelon, C. amarus, has become naturalized in semiarid regions of several continents, and is designated as a "pest plant" in parts of Western Australia where they are called "pig melon".
Taxonomy The sweet watermelon was first described by Carl Linnaeus in 1753 and given the name Cucurbita citrullus. It was reassigned to the genus Citrullus in 1836, under the replacement name Citrullus vulgaris, by the German botanist Heinrich Adolf Schrader. (The International Code of Nomenclature for algae, fungi, and plants does not allow names like "Citrullus citrullus".)Article 23.4 "The specific epithet, with or without the addition of a transcribed symbol, may not exactly repeat the generic name (a designation formed by such repetition is a tautonym)."
The species is further divided into several varieties, of which bitter wooly melon (Citrullus lanatus (Thunb.) Matsum. & Nakai var. lanatus), citron melons (Citrullus lanatus var. citroides (L. H. Bailey) Mansf.), and the edible var. vulgaris are common. This taxonomy originated with the erroneous synonymization of the wooly melon Citrullus lanatus with the sweet watermelon Citrullus vulgaris by L.H. Bailey in 1930.Bailey LH. 1930. Three discussions in Cucurbitaceae. Gentes Herbarum 2: 175–186. Molecular data, including sequences from the original collection of Thunberg and other relevant type material, show that the sweet watermelon (Citrullus vulgaris Schrad.) and the bitter wooly melon Citrullus lanatus (Thunb.) Matsum. & Nakai are not closely related to each other. A proposal to conserve the name, Citrullus lanatus (Thunb.) Matsum. & Nakai, was accepted by the nomenclature committee and confirmed at the International Botanical Congress in 2017.
Prior to 2015, the wild species closest to Citrullus lanatus was assumed to be the tendril-less melon Citrullus ecirrhosus Cogn. from South African arid regions based on an erroneously identified 18th-century specimen. However, after phylogenetic analysis, the closest relative to Citrullus lanatus is now thought to be Citrullus mucosospermus (Fursa) from West Africa (from Senegal to Nigeria), which is also sometimes considered a subspecies within C. lanatus. Watermelon populations from Sudan are also close to domesticated watermelons. The bitter wooly melon was formally described by Carl Peter Thunberg in 1794 and given the name Momordica lanata. It was reassigned to the genus Citrullus in 1916 by Japanese botanists Jinzō Matsumura and Takenoshin Nakai.
History
Watermelons were originally cultivated for their high water content and stored to be eaten during dry seasons, as a source of both food and water. The modern watermelon was first domesticated in Sudan. Kordofan melons from Sudan are the closest relatives and may be progenitors of modern, cultivated watermelons. Watermelon seeds were found in the Dead Sea region at the ancient settlements of Bab edh-Dhra and Tel Arad.
Many 5,000-year-old wild watermelon seeds (C. lanatus) were discovered at Uan Muhuggiag, a prehistoric archaeological site located in southwestern Libya. A 2022 study traced 6,000-year-old watermelon seeds found in the Libyan desert to the Egusi seeds of Nigeria.
In the 7th century C.E., watermelons were being cultivated in India, and by the 10th century had reached China. The Moors introduced the fruit into the Iberian Peninsula, and there is evidence of it being cultivated in Córdoba in 961 and also in Seville in 1158. It spread northwards through southern Europe, perhaps limited in its advance by summer temperatures being insufficient for good yields. The fruit had begun appearing in European herbals by 1600, and was widely planted in Europe in the 17th century as a minor garden crop.
Early watermelons were not sweet, but bitter, with yellowish-white flesh. They were also difficult to open. The modern watermelon, which tastes sweeter and is easier to open, was developed over time through selective breeding.
European colonists introduced the watermelon to the New World. Spanish settlers were growing it in Florida in 1576. It was being grown in Massachusetts by 1629, and by 1650 was being cultivated in Peru, Brazil and Panama. Around the same time, Native Americans were cultivating the crop in the Mississippi valley and Florida. Watermelons were rapidly accepted in Hawaii and other Pacific islands when they were introduced there by explorers such as Captain James Cook.
Seedless watermelons were initially developed in 1939 by Japanese scientists who created seedless triploid hybrids but they did not have sufficient disease resistance. Seedless watermelons became more common in the 21st century, rising to nearly 85% of total watermelon sales in the United States in 2014.
Systematics
A melon from the Kordofan region of Sudan the kordofan melon may be the progenitor of the modern, domesticated watermelon. The kordofan melon shares with the domestic watermelon the loss of the bitterness gene while maintaining a sweet taste, unlike other wild African varieties from other regions, indicating a common origin, possibly cultivated in the Nile Valley by 2340 BC.
Cultivation Watermelons grow in tropical to temperate climates, needing temperatures higher than to thrive. On a garden scale, seeds are usually sown in pots under cover and transplanted into the ground. Ideal conditions are a well-drained sandy loam with a pH between 5.7 and 7.2.
Major pests of the watermelon include aphids, fruit flies, and root-knot nematodes. In conditions of high humidity, the plants are prone to plant diseases such as powdery mildew and mosaic virus. Some varieties often grown in Japan and other parts of the Far East are susceptible to fusarium wilt. Grafting such varieties onto disease-resistant rootstocks offers protection.
+ Watermelon production 63.5 3.7 3.2 2.5 2.0World 105
The United States Department of Agriculture recommends using at least one beehive per acre ( per hive) for pollination of conventional, seeded varieties for commercial plantings. Seedless hybrids have sterile pollen. This requires planting pollinizer rows of varieties with viable pollen. 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 increases to three hives per acre ( per hive). Watermelons have a longer growing period than other melons and can often take 85 days or more from the time of transplanting for the fruit to mature. About a thousand grains of pollen must be delivered and spread evenly on the three lobes of the stigma to make a normal sized and shaped fruit. In addition, lack of pollen is thought to contribute to "hollow heart" which causes the flesh of the watermelon to develop a large hole, sometimes in an intricate, symmetric shape. Watermelons suffering from hollow heart are safe to consume.
Watermelons are an important water source in South Africa, the Kalahari Desert, and East Africa for both humans and animals.
Production In 2024, world production of watermelons was 105 million tonnes, led by China (mainland) accounting for 60% of the total (table). Secondary producers were India, Turkey, Algeria, and Brazil.
Nutrition
Watermelon fruit is 91% water, 6% sugars, and has low content of fat and protein (table). In a reference amount of , watermelon fruit supplies of food energy, with no micronutrients in significant content (table). Watermelon pulp contains carotenoids, including lycopene.
The amino acid citrulline is produced in watermelon rind.
Varieties Various cultivar groups exist:
Citroides group (syn. C. lanatus subsp. lanatus var. citroides; C. lanatus var. citroides; C. vulgaris var. citroides)
DNA data reveal that C. lanatus var. citroides Bailey is the same as Thunberg's bitter wooly melon, C. lanatus and also the same as C. amarus Schrad. It is not a form of the sweet watermelon C. vulgaris nor closely related to that species.
The citron melon or makataan – a variety with sweet yellow flesh that is cultivated around the world for fodder and the production of citron peel and pectin.
Lanatus group (syn. C. lanatus var. caffer)
C. caffer Schrad. is a synonym of C. amarus Schrad.
The variety known as tsamma is grown for its juicy white flesh. The variety was an important food source for travellers in the Kalahari Desert.
Another variety known as karkoer or bitterboela is unpalatable to humans, but the seeds may be eaten.
A small-fruited form with a bumpy skin has caused poisoning in sheep.
Vulgaris group
This is Linnaeus's sweet watermelon; it has been grown for human consumption for thousands of years.
C. lanatus mucosospermus (Fursa) Fursa
This West African species is the closest wild relative of the watermelon. It is cultivated for cattle feed.
Additionally, other wild species have bitter fruit containing cucurbitacin. C. colocynthis (L.) Schrad. ex Eckl. & Zeyh., C. rehmii De Winter, and C. naudinianus (Sond.) Hook.f.
Varieties
The more than 1,200 cultivars of watermelon range in weight from less than to more than ; the flesh can be red, pink, orange, yellow or white.
The 'Carolina Cross' produced the current world record for heaviest watermelon, weighing . It has green skin, red flesh and commonly produces fruit between . It takes about 90 days from planting to harvest.