Common name: Imbe

Ⅰmbe is a fruiting and landscape tree native to sub-Saharan Africa, its natural range extending from Senegal, on the west coast of the continent, east to South Sudan and Ethiopia and from Kenya to South Africa.

It is slow-growing, to heights of up to 17 m (56 ft) in its natural habitat, though is more typically 3 to 7 m (10 to 23 ft) tall and is highly variable in form and shape, with multiple or single trunks and wide-spreading, pyramidal or rounded crowns. The bark is grey or reddish-brown and deeply fissured, sometimes flaking.

The leaves are oval, 10 to 15 cm (4 to 6 in) long, dark glossy green, smooth on the margins and thick, with a leathery texture. They are arranged spirally in threes along the stems and remain on the plant in all seasons.

The flowers are small, fleshy, green petaled with yellow centres and either female or male (on different trees), though with some perfect flowers mixed in. They are borne in tight clusters on mature wood and come into bloom at the beginning of the rainy season, which coincides with spring in its native range.

The fertilised flowers are followed by small round fruit, 2 to 4 cm (0.8 to 1.6 in) in diameter. They have thin, tender skin that is green when young, becoming dull to bright orange, red or purple when ripe, depending on the variety. The skin encloses watery, yellow-orange pulp with one, sometimes two largish seed in the centre.

Use

The fruit when unripe are astringent but when fully ripe have a syrupy pulp and an agreeable sweet-sour to sour flavour, with some variation between the different varieties. They are mostly eaten fresh out-of-hand, but are also good for making jam and can be used to flavour chilled drinks and desserts, such as milkshakes and ice-cream.

It is a suitable ornamental and fruit tree for dry coastal gardens, on account of its evergreen habit, drought, salt and limestone tolerance and edible fruit.

The seedlings make a compatible rootstock for Mangosteen (Garcinia mangostana),  which would allow Mangosteen cultivation to be extended to somewhat drier areas, at least theoretically.

Climate

Grows naturally in dry to moderately humid subtropical and tropical lowland to mid-elevation climates, generally frost-free areas with annual lows of 15 to 25°C, annual highs of 26 to 35°C, annual rainfall of 300 to 1600 mm and a dry season of 3 to 8 months.

Growing

New plants are mostly raised from seed, which should be planted within a few days after removing from the fruit. Female seedlings start to flower and fruit when about five years old. Vegetative propagation, though not commonly practised is worth trying, to try and achieve a good ratio of female to male trees, especially if the goal is to produce fruit.

Performs best on free-draining loam and sand soils of a moderately acid to neutral nature, generally with a pH of 5.0 to 7.0, and on sites with full to partial sun exposure.

Problem features

Imbe produces fruit with viable seed, but there does not appear to be any record of it anywhere as having escaped cultivation, a weed or an invasive species.

Books

• Barwick, M., et al. 2004, Tropical & subtropical trees : a worldwide encyclopaedic guide, Thames and Hudson, London

• Food and Agriculture Organization of the United Nations (FAO) 1988, Traditional food plants : a resource book for promoting the exploitation and consumption of food plants in arid, semi-arid and sub-humid lands of eastern Africa, Food and Nutrition Paper No. 42, Rome

• Kennard, W. C. & Winters, H. F. 1960, Some fruits and nuts for the tropics, Miscellaneous Publication No. 801, U.S. Department of Agriculture, Federal Experimental Station, Mayaguez, Puerto Rico

• 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.

• National Research Council (Board on Science and Technology for International Development) 2008, Lost Crops of Africa: Volume III: Fruits, The National Academies Press, Washington D. C.

• Roecklein, J. C & Leung, P.S. 1987, A Profile of economic plants, Transaction Books, New Brunswick, New Jersey