Winter melon

Winter melon (Benincasa hispida) is an annual herbaceous vine of the cucumber family (Cucurbitaceae), with long bristly stems climbing by branched tendrils. Leaves are large, alternate, broadly heart-shaped, 10–25 cm across, shallowly 5–7 lobed with toothed margins and soft hairs on both surfaces, on long stalks. Flowers are large and yellow, unisexual and monoecious, opening in the late afternoon and evening to attract night-flying insects; the female flower bears a densely hairy ovary. The fruit is very large, cylindrical to oblong, 25–60 cm long and 15–25 cm across, sometimes weighing tens of kilograms; the green skin is covered with a white waxy bloom — the feature behind the name 'wax gourd'. The flesh is thick and watery, and flat ivory-white seeds lie within the spongy core.

The species is native to South and Southeast Asia and has long been cultivated in India, China, Japan and throughout Southeast Asia; in Vietnam it is grown widely in the lowlands and peri-urban areas, trained on trellises by ponds or trailing on the ground, fruiting from late summer to autumn. Young fruit is boiled or stir-fried; mature fruit goes into soups (mướp/bí soup with shrimp), braises and bone broths, while the mature flesh is candied into mứt (mooncake filling and Tết sweets). Because of its waxy coating the fruit keeps for months — the Chinese name 'dong gua' means 'winter melon'. In traditional medicine winter melon is sweet and cooling: it clears heat and toxins, promotes urination and reduces oedema, and eases scanty urine; the seeds (dong gua ren) are used for cough and phlegm, and the rind as a diuretic. The flesh is a low-energy, heat-clearing food considered helpful for those who are overweight or puffy with water retention.