The water melon (Cucumis melo) is a main crop in several farming areas particularly around Dhaid, while the cucumber (Cucumis sativus), marrow (Cucurbita melo) and pumpkin (Cucurbita maxima) are also grown to a lesser extent, especially in Ras al Khaimah and around Al Ain. However, in the natural plant community of the IUAE there are only two genera, Citrullus colocynthis and Cucumis prophetarum, both inedible, prostrate perennials.Citrullus colocynthis (L.) Schrade
This is the larger and more common of the two with stems trailing for up to ten metres from a woody rootstock. Stems and branches are annual or more often depending on seasonal rainfall variations, and quite rough to touch because of a dense covering of short, stiff hairs. Leaves are on long stalks, roughly triangular in outline, up to 12 cm long with 3 - 5 indented and pointed lobes, crisped at the margins. Flowers are solitary, facing upwards, with pale yellow petals and a darker centre of stamens, the whole up to 3 cm across, March to August but very variable. The fruit is applesized, up to 10 cm in diameter, at first with green and yellow vertical stripes that mature to a sulphur-yellow, very smooth. The Iinside is pulpy at first, eventually becoming mostly hollow with the dark brown seeds loose inside.
This desert gourd is represented in all Emirates in a variety of habitats except upper mountain elevations. It is found throughout open sandy desert in the triangle formed by Abu Dhabi, Al Ain and Ras al Khaimah, occasionally in coastal towns and in plantations in the Western Region.
The fruit is very bitter and normally avoided by animals because of its drastic purgative effects. Small rodents sometimes scrape the rind. As the annual foliage dies back the lightened fruit becomes detached from its stalk and is blown across the desert or buried in nearby sand.Cucumis prophetarum Jusl. ap L.
With stems trailing to 1.5 metres and often half-hidden in vegetation, this species is much less frequently recorded. Stems are light green, grooved; and diverging at the joints, also stiffly hairy and, like C. colocynthis, sprouts tendrils at the base of the leaf stalks. Leaves are palmate with 3 -5 lobes, distinctly veined, and crisped at the margins, on 2 -4 cm stalks. Flowers are often more orange than C. colocynthis, Variable between February and July. A major distinguishing feature is the fruit, which is plum-sized and covered with blunt, spine-like tubercles; the small gourd is striped longitudinally green and yellow, maturing to a very bright yellow, containing many seeds in white pulp.
This gourd is found mostly in the mountains, foothills and on alluvial gravels in the east and north of the country, very rarely. in open sand. It is frequently recorded in oases and fringing gardens but often in dense undergrowth and it never attains the extensive size of C. colocynthis. It has been recorded on bare rocks just above mean high tide level at Khor Fakkan. The fruit is ignored.