Common Name: Water Melon

General Information

Citrullus lanatus is an annual plant, producing stems up to 4 metres long, occasionally to 10 metres. These stems climb with the help of tendrils or, more frequently, trailing along the ground[].
A very popular fruit, cultivated from the tropics to the warm temperate zone, and widely available in markets. The plant has many other uses, including providing an oil, and has many medicinal properties.

Known Hazards

The sprouting seed produces a toxic substance in its embryo[].

Botanical References

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Range

Tropical and S. Africa

Habitat

A weed of roadsides and open ground in desert areas[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Annual
Height	0.50 m
Pollinators	Insects
Self-fertile	Yes
Cultivation Status	Cultivated

Cultivation Details

Water melon is a plant of the drier tropics, though it can be cultivated from the moist tropics to the warm temperate zones. In the tropics it can be found at elevations up to 1,000 metres. It grows best in areas where annual daytime temperatures are within the range 20 - 35°c, but can tolerate 15 - 40°c[]. The plant is not frost hardy and requires a long hot summer if it is to fruit well outside the tropics. It prefers a mean annual rainfall in the range 500 - 700mm, but tolerates 400 - 1,800mm[]. Plants grow best in dry, sunny periods - excessive moisture and high humidity reduce flowering and lead to leaf diseases[]. Temperatures above 30°c can reduce fertilization and lead to lower yields[]. It prefers regions with stable day/night temperatures[].
Prefers an organic-rich sandy loam and a very sunny position[, , , ]. Prefers a pH in the range 6 - 7, tolerating 5.5 - 7.5[]. A drought resistant plant once established, it is intolerant of wet soils[].
In general, fruit harvest commences 80 - 110 days from sowing, continuing for a further 40 - 50 days[].
The yield of seeds from the bitter melons can vary considerably from 250kg per hectare to over 3,000kg depending on cultivar and soil.
Yields of watermelon fruits can vary from 5 - 60 tonnes per hectare, with an average around 25 tonnes[].
Yields of the cooking melons have exceeded 100 tonnes per hectare in trials[].
Three main types of water melon are grown:-
Sweet varieties (also known as subsp vulgaris). These are often 30cm or more in diameter and contain a sweet, very juicy flesh that is eaten raw. This is the form of water melon that is best known outside of Africa[].
Bitter forms (also known as subsp mucosospermus). This form has a bitter-tasting almost inedible flesh, and is grown mainly for its edible seeds. Widely used in Africa, though little known elsewhere[].
Cooking forms (also known as subsp lanatus). Neither sweet nor bitter, these forms are used as a vegetable, usually being cooked when immature[].
There are many named varieties[, ]. The cultivars 'Fordbrook hybrid', New Hampshire midget' and 'Sugar baby' commence bearing in 80 - 85 days in Long Island, New York[].
A good companion plant for potatoes[].

Edible Uses

Fruit - raw or cooked. A very refreshing fruit[, , , , ], the best forms have a delicate sweetness with an extremely high water content. The fruit is often used as a refreshing drink[]. The unripe fruits are added to soups[]. A syrup can also be made from the juice[]. The fruit is a rich source of pectin[, ], and can be added to pectin-low fruits when making jam[]. Pectin is said to protect the body against radiation[]. The fruit varies considerably in size from cultivar to cultivar, but can be up to 1 metre long and 40cm wide[]. A nutritional analysis is available[].

Leaves - cooked and used as a vegetable[].

Seed - raw or cooked[, , , ]. They can be roasted or ground into a powder and used with cereal flours when making bread, cakes etc, or added to soups and stews[, , ]. The seeds are considered a delicacy in Africa and are used in a variety of ways. The can be eaten raw; after roasting, they can ground into a coarse, whitish meal, which is nutritious and pleasantly nutty-tasting; they can be made into pulp and added as a thickener to soups; they are fermented to produce a sweetener locally called 'ogiri'; roasted and pounded, they can be wrapped in leaves and then boiled to produce another sweetener called 'igbãlo'; the pulp of roasted and salted seeds is eaten[]. The seed contains about 30% protein, 20 - 40% oil[].

An edible oil is obtained from the seed[, , , ]. Highly prized, it is used for cooking[].

The roasted seed can be used as a coffee substitute[].

Medicinal

The seed is demulcent, diuretic, pectoral and tonic[, ]. It is sometimes used in the treatment of the urinary passages[] and has been used to treat bed wetting[]. The seed is also a good vermifuge[] and has a hypotensive action[]. A fatty oil in the seed, as well as aqueous or alcoholic extracts, paralyze tapeworms and roundworms[].

An emulsion of the seeds and crushed leaves makes an excellent cataplasm applied warm as a treatment for intestinal inflammation[].

The fruit, eaten when fully ripe or even when almost putrid, is used as a febrifuge[] The fruit is also diuretic, being effective in the treatment of dropsy and renal stones[]. The fruit contains the substance lycopine (which is also found in the skins of tomatoes). This substance has been shown to protect the body from heart attacks and, in the case of the tomato at least, is more effective when it is cooked[].

The rind of the fruit is prescribed in cases of alcoholic poisoning and diabetes[].

The root is purgative and in large dose is said to be a certain emetic[].

Agroforestry Uses:

The plant grows well in mixed plantings with maize[].

Other Uses

The seed contains 20 - 40% of a highly prized oil. As well as being edible, it is also used in cosmetics, for making soap and for lighting[, , , ].

Face masks made from the fruit are used as a cosmetic on delicate skins[].

Propagation

Seed - sow spring in a rich compost in a greenhouse. Either put 2-3 seeds in each pot and thin to the best plant, or prick out the seedlings into individual pots of rich soil as soon as they are large enough to handle. Grow them on fast and, if trying them outside, plant out after the last expected frosts. Give them some protection, such as a cloche or a frame, at least until they are growing away vigorously.