Common name: Abiu

Abiu is a fruit-bearing tree originating in the humid forests of the Amazon, its natural range extending across large parts of Peru and Brazil. It is closely related to the Star Apple (Chrysophyllum cainito) and Sapodilla (Manilkara zapota) and has long been cultivated in its native South America. More recently, it has been introduced and cultivated in South Florida, Malaysia and northern Australia.

It is a fast-growing tree and may reach 15 m (50 ft) or more in height in native forests, though it is typically 5 to 10 m (15 to 30 ft) tall with a short trunk and a densely branched, wide-spreading crown. The bark is grey or brown, smooth on young trees becoming rough and cracked with age. Except for the leaves and flowers, all parts of the tree exude a sticky white latex when wounded.

The leaves are up to 25 cm (10 in) long, lance-shaped, tapering to points at both ends, glossy green on top and arranged alternately in clusters at the ends of the branches. They are evergreen, persisting on the tree in all seasons.

The flowers are small, white and mostly bisexual, with both female and male parts. They are borne singly or in clusters of up to eight directly on the branches and bloom at their fullest from spring to summer, with light blooms at other times in constantly humid areas.

The flowers develop into nippled egg-shaped fruit of variable size, ranging from 5 to 12 cm (2 to 5 in) in diameter. They mature around three months after fruit-set, usually from summer to autumn in its native range, but with fruit produced nearly year-round in constantly humid climates. When ripe, they are bright yellow with a smooth, thin, leathery rind enclosing soft, jelly-like pulp. At the centre sit one to four large, smooth, brown oval seed.

Use

The ripe fruit pulp is eaten fresh out-of-hand or is spooned out and used in chilled desserts. It is soft, white to cream-coloured, translucent and somewhat jelly-like, with a sweet, subtle caramel-like flavour. Care is taken to avoid the sticky latex found close to the rind on the inside of the fruit.

Health use

The fruit pulp contains very high levels of Vitamin C (Ascorbic acid) and good levels of Vitamin B3 (Niacin).

Climate

Grows and fruits naturally in humid subtropical and tropical climates, generally frost-free areas with annual lows of 15 to 25°C, annual highs of 24 to 35°C, annual rainfall of 1300 to 4000 mm and a dry season of 5 months or less. Abiu trees may fail to thrive in areas where the average low of the coldest month is below 10°C (50°F).

Growing

New plants are usually started from cuttings or seed, with each method having its advantages and disadvantages. The cuttings exude a sticky latex, making them challenging to propagate. Seed-grown trees sometimes produce fruit with characteristics different from that of the parent tree. The seed also lose their viability quickly, usually one to two days after extracting from the fruit.

Abiu performs best on rich, free-draining clay and loam soils of a moderately acid to neutral nature, generally with a pH of 5.5 to 7.5, and on sites with full to partial sun exposure. It has poor tolerance to salt spray, soil salt and limestone soil conditions.

It is an early maturing, heavy bearing fruit tree. Some six-year-old trees reportedly yield up to five hundred fruit a year and flowering and fruiting starting in trees as young as two to three years old. Mulching to minimise water stress during dry periods and the periodic application of potassium and phosphorus-rich manures help increase survival rates and improve fruit production and quality.

Problem features

Abiu trees produce a significant amount of fruit, and the seed, although short-lived, survive passage through an animal's gut. At least one reference publication lists it as a weed. Still, there does not appear to be any record of it as a serious weed anywhere in the world. It is assessed to be a low weed risk species for Hawaii by the Hawaii Pacific Weed Risk Assessment (HPWRA) project..

Books

• Food and Agriculture Organization of the United Nations (FAO) 1986, Food and Fruit-bearing Forest Species, 3 : Examples from Latin America, FAO Forestry Paper no 44/3, Rome

• Janick, J., & Paull, R. E. 2008, The encyclopedia of fruit & nuts, CABI Publishing, Wallingford, Oxfordshire

• Macmillan, H. F. 1943, Tropical planting and gardening : with special reference to Ceylon, 5th ed, Macmillan Publishing, London

• Martin, F. M., et al. 1987, Perennial edible fruits of the tropics : an inventory, U.S. Dept. of Agriculture (USDA), Agricultural Research Service, U.S. Government Printing Office (GPO), Washington, D.C.

• Morton, J. F. & Dowling, C. F. 1987, Fruits of warm climates, Creative Resources Systems, Winterville, North Carolina

• Norrington, L. & Campbell, C. 2001, Tropical food gardens : a guide to growing fruit, herbs and vegetables in tropical and sub-tropical climates, Bloomings Books, Hawthorn, Victoria

• Page, P. E. 1984, Tropical tree fruits for Australia, Queensland Department of Primary Industries (QLD DPI), Brisbane

• Queensland Department of Primary Industries and Fisheries (QLD DPI) 2008, Queensland tropical fruit : the healthy flavours of North Queensland, Brisbane

• Randall, R. P. 2007, The introduced flora of Australia and its weed status, Cooperative Research Centre for Australian Weed Management, Glen Osmond, South Australia

Articles, Journals, Reports and Working Papers

• Watson, B.J., & Moncur, M. 1985, Guideline criteria for determining survival, commercial and best mean minimum July temperatures for various tropical fruit in Australia (Southern Hemisphere), Department of Primary Industries Queensland (DPI QLD), Wet Tropics Regional Publication, Queensland