Annual herbaceous vine

Stem: round to angular and hairy.

Leaves: alternate, stalked, 10 - 18 cm long, egg-shaped to oblong in outline with a heart-shaped base, pinnately lobed with the lobes often lobed again.

Flowers: either male or female, found on the same plant (monoecious), borne solitary in leaf axils, short-stalked, yellow, about 3.8 cm across, with five sepals and a five-parted corolla that is flat and circular in outline. The male flowers have three stamens, while the female flowers have an inferior ovary.

Fruit: a spherical to oblong berry with a thick rind (pepo), dark to light green, often mottled or striped, to 0.6 m long, with red, orange, yellow, or white flesh. The many seeds are white, black, or reddish, 5 - 15 mm long, flat and smooth.

Tendrils: branched.

Similar species: Cucurbita species differ by having bell-shaped flowers. Cucumis melo differs by having unbranched tendrils and shallowly lobed leaves.

Flowering: September

Habitat and ecology: Introduced from tropical Africa, this species occasionally grows around dumps, grain elevators, railroad ballasts, pond shores, and near picnic areas.

Occurence in the Chicago region: non-native

Etymology: Citrullus is a diminutive of Citrus, referring to some similarity of the fruit. Lanatus means wooly.

Author: The Morton Arboretum

Duration: Annual

Nativity: Non-Native

Lifeform: Vine

General: Herbaceous annual; stems prostrate or creeping on the ground, with curly tendrils, covered in long, spreading hairs, particularly when young, to 10m long.

Leaves: Leaves more or less narrowly ovate in outline, up to 20 19 cm, usually deeply palmately 3-5 lobed with lobes elliptic in outline and often lobed again; hairy when young, particularly on the veins beneath, becoming roughly punctate when older; margins almost entire or obscurely and finely sinuate-dentate.

Flowers: Flowers solitary, axillary, yellow, unisexual on the same plant; corollas 3-4c cm wide, with 5-parted corolla.

Fruits: Smooth, greenish with darker mottling; wild plants 1.5-20 cm long, cultivated fruits much larger and often more elongated ellipsoid, up to 60 30 cm.

Ecology: Agricultural areas and escaped in waste areas, roadsides, river banks, upland slopes, sandy washes.

Distribution: Introduced to most of the world, and most of the southern half of the US, midwest and eastern US.

Notes: Originally from West Africa, this is the common cultivated watermelon. Fruits range from 1.5-20 cm long in wild populations to 60 cm in cultivated plants. It has become naturalized in some areas of North America. Distinguished by its annual, prostrate, vine-like habit and deeply palmate, 3-5 lobed leaves which are up to 20 cm long and ovate (egg shaped) in outline.

Ethnobotany: Although the age of domestication of watermelon is not known, it is known to have been cultivated at least as early as 1500 BC in West Africa as early as the 1500 and seeds have been found in many Egyptian tombs and archaeological sites. From there it spread throughout the world. It reached the new world and was being grown by Spanish and Native Americans by the 1500s. The plant has many genetic varieties in various parts of the world and number especially high in Africa. In many regions there are multiple medicinal uses.

Etymology: Citrullus is from Citrus, as the fruits were thought tto be similar and lanatus comes from lana or lanate, -wooly-, referring to the long hairs on stems and some fruits and leaves.

Synonyms: None

Editor: FSCoburn 2014