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  • Robusta - the species

    Coffea canephora, popularly known as robusta because of the hardy nature of the plant, was first discovered in the former Belgian Congo in the 1800s. It is also known to be indigenous to the tropical forests around the Lake Victoria crescent in Uganda. It was introduced into South-east Asia in 1900, after coffee rust disease wiped out all arabica cultivation in Ceylon in 1869 and destroyed most low altitude plantations in Java in 1876. Currently it represents between 30% and 40% of world production. It is grown in West and Central Africa, throughout South-east Asia, and in parts of South America including Brazil, where it is known as Conillon.

    The robusta plant grows as a shrub or as a small tree up to 10 m in height. Generally, it is planted at lower densities than arabica because of the larger plant size. Robusta exists in many different forms and varieties in the wild. The cross-bred strains of this variety of coffee are often hard to identify, but two main types are generally recognized: Erecta, or upright forms, and Nganda, or spreading forms.

    Robusta is a diploid species. It is a larger bush than the arabica plant, and with robust growth. The root system of robusta, though large, is rather shallow compared to arabica, with the mass of feeder roots being confined to the upper layers of the soil. The leaves are broad, large and pale green in colour. Flowers are white and fragrant, and are borne in larger clusters than in arabica. The flowers open on the seventh or eighth day after receiving rain. Unlike arabica, robusta is self-sterile, that is, its ovule cannot be fertilized with its own pollen and hence cross-pollination is necessary. The cherries are small, but larger in number per node than arabica, varying from 40 to 60 or more. They mature in about 10 to 11 months and are generally ready for harvest two months later than arabica.

    Robusta beans are smaller than arabica beans. Depending on the plant strain, the bean shape is round, oval or elliptical with pointed tips. The colour of the beans depends on the method of processing - grey when washed and golden brown when prepared by the dry cherry or natural method of preparation. The caffeine content of robusta beans is nearly twice as high as that of arabica beans (2%-2.5% versus 1.1%-1.5%).

    Robusta coffee possesses several useful characteristics such as high tolerance to leaf rust pathogen, white stem borer and nematode invasion, and the potential to give consistent yields. For these reasons, the cost of robusta cultivation is relatively low compared to the arabica variety. On the other hand, inability to endure long drought conditions, late cropping, late stabilization of yields and slightly inferior quality compared to arabica, are some of the negative attributes of robusta coffee.

    In general, robusta is hardier than arabica and grows well at low altitudes, in open humid conditions, with the cost of production being lower than the arabica variety. In some countries (Uganda and India, for example) robusta is also cultivated at fairly high altitudes (above 1,200 m) and under shade. These features have helped in the production of dense beans, with better cupping characteristics than those normally expected in the robusta cup, which could aid in the preparation of specialty and possibly exemplary coffees.