Common name: Calamansi

Calamansi is a citrus family member, a natural hybrid of Kumquat (Citrus japonica) and Mandarin (Citrus reticulata). One of the most common backyard fruit trees in the Philippines, it is also cultivated commercially there, particularly in Oriental Mindoro Province, for its fruit, with the juice used as a citrus flavouring and souring agent.

In tropical areas, it may grow into a small tree up to 7.5 m (25 ft) tall, though elsewhere it is typically 3 to 5 m (10 to 16 ft) tall with a low-branching habit, forming a densely leafy rounded crown. The branches are thin and armed with sharp thorns.

Leaves are oval, 4 to 7 cm (1.6 to 2.8 in) long, dark glossy green on top, pale green underneath and alternately arranged and clustered at the ends of the branches. They give off a citrusy aroma when crushed and remain on the plant year-round.

Flowers are five-petaled, white with pale yellow centres, 2.5 cm (1 in) wide and borne singularly or in clusters of two or three at the branch tips. They are sweetly fragrant, bloom almost year-round, and, if fertilised, develop into small, round fruit 3 to 4.5 cm (1.2 to 1.6 in) in diameter.

The fruit peel is dark green in tropical lowland areas, becoming pale green or green-yellow when ripe, resembling a lime (Citrus aurantiifolia). However, the peel develops a bright orange colour in cooler warm-temperate, subtropical and tropical highland areas.

The pulp is deep orange, juicy, and arranged in segments like an orange, with or without seed. Numerous oil glands dot the peel, giving the fruit a glossy surface and a pleasing, citrusy aroma. The peel is not easily removed when young but becomes less adherent and easier to peel away as the fruit ripens.

Fruit (Farmers Market, Bangkok, Thailand)

Cicada Market in Hua Hin, Thailand

Edible uses

Souring agent - Juice squeezed from the fruit has a pleasing sour citrus flavour and is widely used as a souring agent, particularly in the Philippines, Thailand, Malaysia and Indonesia.

Natural flavouring - As well as a flavouring in beverages, including soft drinks. A large proportion of the juice produced in the Philippines is pasteurised and made into a juice concentrate, which is used directly as a flavouring in bottled citrus drinks sold throughout the country.

Fruit in syrup or juice - The whole or sliced fruit is preserved in syrup.

Fruit spread - Or made into marmalade.

Candied fruit - Or sugared and dried to make candied fruit.

Honey - The flowers produce plenty of nectar, enough to make honey. The honey is orange-amber, fluid, and aromatic, with a rich, pleasing flavour and slightly acid aftertaste.

Environmental uses

Bee forage - Sustains honeybee colonies, which can be observed actively working the flowers.

Container plant - Suitable for growing in containers.

Home garden tree - And as an ornamental fruit tree in gardens, in climates ranging from tropical to warm-temperate.

Climate

Grows and fruits naturally in humid warm-temperate, subtropical and tropical climates, generally frost-free areas with annual lows of 9 to 25°C, annual highs of 18 to 37°C, annual rainfall of 600 to 3000 mm and a dry season of 5 months or less.

Growing

New plants can be raised from seed or by vegetative propagation. Performs best on well-manured, free-draining loam and sand soils of a moderately acid to neutral nature, generally with a pH of 5.5 to 7.0, and on sites with full to partial sun exposure. It has poor tolerance to slow-draining or permanently wet soils.

Problem features

It is listed as a weed in at least one reference publication. Still, it appears to have no record as a serious weed, despite its widespread introduction and cultivation. The Hawaii Pacific Weed Risk Assessment (HPWRA) project assesses it as a low weed-risk species for Hawaii.

Books

• Allen, B. M. 1967, Malayan fruits : an introduction to the cultivated species, Donald Moore Press, Singapore

• Elevitch, C. R. 2006, Traditional trees of Pacific Islands: their culture, environment and use, 1st edition, Permanent Agriculture Resources, Holualoa, Hawaii

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

• Randall, R. P. 2002, A global compendium of weeds, R.G. and F.J. Richardson Press, Melbourne

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

• Saunt, J. 1990, Citrus varieties of the world : an illustrated guide, Sinclair International, Norwich, England

Articles, Journals, Reports and Working Papers

• Morton, J.F. 1964, Honeybee Plants of South Florida, Proceedings of the Florida State Horticultural Society, Vol 77:415-436.