Ziziphus mauritiana, also known as Indian jujube, Indian plum, Chinese apple, ber (Hindi: बेर) and dunks, is a tropical, spiny, evergreen shrub or small tree in the buckthorn family Rhamnaceae. It is often confused with the closely related Chinese jujube (Z. jujuba): Z. mauritiana is common is tropical and subtropical climates, while Z. jujuba prefers temperate climates. The plant grows vigorously up to 12 metres (39 ft) high, with a trunk 30 centimetres (12 in) or more in diameter. It has a spreading crown with stipular spines and drooping branches. The fruit is oval, obovate, oblong or round, and can be 2.5–6 centimetres (0.98–2.36 in) long depending on the variety, having smooth, light green skin when unripe, turning yellow and then reddish brown as it ripens.
Origin and Distribution The species is believed to be native to South Asia, southern China, Southeast Asia, and Central and West Africa. It has been introduced to the tropical regions of the Americas, and is now widely naturalised throughout the Old World tropics from Southern Africa through the Middle East to South Asia and China, into Australasia and the Pacific Islands. While the Rhamnaceae family contains many nitrogen-fixing species, Z. mauritiana can form dense stands and become invasive in some areas, including Fiji and Australia, where it has become a serious environmental weed. The species name mauritiana likely references the island of Mauritius, despite the species not being native there, due to trade routes or the movement of plant specimens through the region during the 18th century when Mauritius was an important colonial hub. In taxonomy, newly described species were historically often associated with the nearest or most significant landmasses known at the time of discovery, rather than the exact location where the species was found.
Morphology
Ziziphus mauritiana has a rapidly developing taproot, a necessary adaptation to drought conditions. The species varies widely in height, from a bushy shrub 1.5–2 metres (4.9–6.6 ft) tall, to a tree 10–12 metres (33–39 ft) tall with a trunk diameter of about 30 centimetres (12 in). Z. mauritiana may be erect or wide-spreading, with gracefully drooping thorny branches and zigzag branchlets, with short, sharp straight or hooked thorns; some varieties are thornless. The leaves are alternate and ovate or oblong-elliptic in shape with rounded apices, with three main longitudinal veins originating from the petiole. The size of the leaves ranges from 2.5–6.3 centimetres (0.98–2.48 in) long and 2–4 centimetres (0.79–1.57 in) wide. The upperside (adaxial surface) of the leaves is dark-green and smooth, while the underside (abaxial surface) is covered with hairs. The flowers are tiny and yellow with five petals, located on leaf axils. They open fully in the early morning or later in the day, depending on the cultivar. Fertilisation relies on cross-pollination by insects attracted by the odour and nectar. Pollination is done by honeybees, wasps (Polistes sp.) and houseflies. Due to the protandrous nature of the flowers, the trees cannot reliably self-pollinate. The unpleasant scent of the flowers is caused by skatole, a volatile organic compound released at high concentrations at anthesis.
This fast-growing tree bears fruit within three years. The fruit is an oval, obovate, round or oblong drupe that measures 2.5 centimetres (0.98 in) diameter, though in some cultivars it can measure up to 6 centimetres (2.4 in) long and 4 centimetres (1.6 in) wide. When unripe, the skin is light green in colour while the flesh is white and crispy, with a bland, sour or slightly sweet flavour. The ripe fruit has a pleasant aroma and a soft, juicy and somewhat mealy texture, with wrinkled skin and a sweet-sour taste. Overripe fruits are more wrinkled, and the flesh becomes soft, spongy and buff-coloured with a musky scent. Each fruit contains an oval or oblate rough pit, containing one or two ellipsoid red-brown kernels, each measuring 6 millimetres (0.24 in) long.
Ecology This hardy tree can withstand extreme temperatures and thrives in rather dry or water-logged conditions with an annual rainfall of 125–2,225 millimetres (4.9–87.6 in). In Fiji, naturalised trees grow along roadsides and on agricultural land, usually near sea level but occasionally up to an elevation of 600 metres (2,000 ft). It also grows well on laterite soils with good drainage, or sandy, gravelly, alluvial soil of dry riverbeds. In Australia, this species grows on a wide variety of soil types, including cracking clays, solodic soils and deep alluvials, in tropical and subtropical areas with an average annual rainfall of 470–1,200 millimetres (19–47 in). In the drier parts of this range, it grows best in riparian zones. Commercial cultivation usually extends up to 1,000 metres (3,300 ft). Above this elevation, the trees do not grow well, and cultivation becomes less economical. While this species can withstand extreme conditions, it is more widespread in areas with an annual rainfall of 300–500 millimetres (12–20 in). In China and India, it grows wild up to an elevation of 1,650 metres (5,410 ft). The minimum temperature for survival is 7 °C (45 °F) and the maximum is 50 °C (122 °F). Studies report that this species flourishes in alkaline soils with a pH as high as 9.2. However, deep sandy loam to loamy soils with neutral or slightly alkaline pH are considered optimum for growth.
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