Wild melon or Paddymelon 
 Wild melon

Wild melon biology
Citrullus lanatus (Thunb.) Matsum. & Nakai var. lanatus
Family: Cucurbitaceae (Melon family).

Common names: Wild melon, Afghan melon, Bastard melon, Bitter apple, Bitter melon, Camel melon, Jam melon, Mickey melon, Paddy melon, Pie melon, Watermelon.

Confused with: Colocynth (C. colocynthis) and Prickly paddy melon (Cucumis myriocarpus). The commonly cultivated watermelon is Citrullus lanatus var. caffer.

Description:

Seedling leaves - are oval shaped with a small notch at the leaf tip, 30 mm long and 20 mm wide, borne on a short stalk 3 mm long.

Early leaves - the first true leaf is roughly circular to triangular and has a long bristly stalk, wavy margins and pale veins. This leaf is notched at the base. The second true leaf is similar in shape but has three to five deep lobes.

Adult leaves - have three to seven deep lobes, the middle lobe being the longest, the whole leaf deeply divided into crinkly lobes. The leaves are 20 - 200 mm long, 25 - 190 mm wide and are oval to heart-shaped. These leaves are generally hairless on the upper surface but have short hairs on the lower surface that make them rough to touch. There are long hairs on the leaf veins. The leaf stalk is also rough to touch, and is 20 - 120 cm long.

Plants - are prostrate vines, covered in long soft hairs with stems up to three metres in length that are woolly towards the tip. The long tendrils (thread-like structures at the tip of the stem) are often forked. The plant has a solid taproot with numerous lateral root branches.

Flowers - the plant produces yellow five-petalled male and female flowers, both on the same plant. The male flowers have petals that are 6 - 16 mm long, on stalks 10 - 80 mm long, while the female flowers petals are about 10 mm long on stalks 3 - 40 mm long. Both male and female flowers are 30 - 40 mm in diameter and tubular. The flowers are produced singly in the leaf axils.

Fruits - the fruits are melon-like, spherical to oblong, from 6 - 30 cm in diameter, smaller than cultivated melons, and bitter to taste. They are hairy, dark green, mottled with pale green or yellowish, long stripes, and contain a white flesh.

Seeds - initially the seeds are white but become brown with black stripes when mature. They are oval-shaped and flat, 9 - 10 mm long and 6 mm wide.

Lifecycle/Biology: This annual weed germinates well during periods of warm weather and rainfall, often following spring and summer rains. Its growth is rapid as temperatures increase, particularly over summer. Flowers and fruits develop during summer and autumn, and the plant dies off in autumn. The deep taproot allows the plants to be extremely drought tolerant once established, with plants rarely dying without fruiting. The seeds can be blown by wind or carried along in water.

Ecology: Widespread throughout mainland Australia. A common species in semi-arid areas. The plant is often found on sandy or flooded soils, along roadsides, neglected areas, watercourses, channels, and also in cultivated situations. The density of the weed varies from year to year, depending on moisture.

The problem: Commonly found in channels and other areas that retain soil moisture. The seeds are readily spread via irrigation water and appear to remain dormant for several years. Dense stands can be very competitive and deplete the soil of water and nutrients. The long dead stems may also tangle in implements.

Distribution: Found throughout Australia.

Origin: A native of Africa.

References:

Plants of Western New South Wales, p. 624 - 625.

Crop Weeds of Northern Australia, p. 145 - 146.




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