Cassava, Manihot esculenta

Cassava is one of the most important staple foods in the world. For hundreds of millions of people, it is an essential part of their diet. The plant impresses with its flexibility in cultivation and provides a lot of carbohydrates – so it’s no wonder that it has become so popular.

Flexible wonder

Cassava is a plant species from the genus Manihot in the spurge family (Euphorbiaceae). Alongside the rubber tree, cassava is the only spurge plant on our Global Field. The large root fruits have many names: ‘mandioca’ in Brazil, Argentina and Paraguay, cassava on the African continent and in Spanish-speaking South America it is known as yuca. The plant is widely cultivated because of its starchy root tubers. The processed starch is called tapioca.

Cassava plants are perennial shrubs that grow up to five meters high. The seedlings of the plants develop deep taproots, whose fibrous lateral roots then thicken and form the popular, large, spindle-shaped root tubers. These are very starchy – around 40 percent of the tubers consist of starch. All parts of the cassava plant produce milky sap.

The cassava plant bears both male and female flowers, both of which are found on the same plant. The female flowers ripen before the male flowers so that self-pollination is avoided. Some varieties no longer produce flowers, while others only a small number.

Although cassava plants prefer fertile, sandy-loamy soils, they also grow in dry, nutrient-poor soils. The plant grows well everywhere between 30 degrees latitude north and south, i.e. on the equatorial belt. However, only here, as it is sensitive to frost and needs almost a whole year to grow. If there is no frost, however, it can adapt to many ecosystems. In addition, it basically does not matter when it is sown and harvested. This flexibility makes it an ideal plant for food security in dry and nutrient-poor regions.

From the ‘food of the poor’ to a staple food

The plant originally comes from South or Central America and has been cultivated for food for around 9000 years. The cultivated cassava varieties probably originate from the southern regions of the Brazilian Amazon. Cassava was already being cultivated in Bolivia over 10,000 years ago. From there, the plant spread to many areas of South and Central America.

As with so many arable crops, the global spread of cassava began with the colonial occupation by European countries – in this case Portugal and Spain. The Spaniards discovered the plant in the Caribbean and the Portuguese in what is now Brazil; writings from this time report on “bread made from poisonous roots”. In the Central and South American colonial societies, cassava quickly became very important for feeding the settlers and slaves. While the fertile land was used to grow sugar cane, less fertile fields were planted with cassava. Impoverished farmers and runaway slaves grew cassava and sold it in cities and to sugar planters.

The Portuguese brought cassava to Africa, both in the form of flour or bread as food for the slaves during their transportation from Africa to America, and in the form of plants that were to be propagated in Africa. Along with the plants, the knowledge of how to grow them and, above all, how to process them correctly had to be passed on. Cassava was introduced to Asia in the 17th century. In Indonesia and India, too, cassava cultivation was promoted by the colonial powers – with the aim of avoiding famine.

While cassava was propagated as the ‘food of the poor’ during the colonial era, cultivation only intensified enormously from the 1980s onwards. For a long time, cassava cultivation was seen as ‘non-intensifiable’, partly because the intensification approach of the Green Revolution, i.e. the development of dwarf varieties, the use of chemicals and irrigation, was not suitable for rain-fed cassava plants and partly because it was hardly researched as it was a plant of the Global South. In recent decades, however, cassava has become increasingly popular as a staple food, particularly in sub-Saharan Africa. The area under cultivation has more than doubled since 1980 and yields have also been increased by the many smallholder farmers.

In Asia, on the other hand, Thailand in particular dominated cassava growth for a long time. Here, cassava was discovered as animal feed and an export commodity. In the 1980s, Thailand began exporting dried cassava to Europe as animal feed – Vietnam, Indonesia and China were soon competing with Thailand on the export market. The dry cassava chips were soon also discovered as a source for ethanol production, giving a further boost to cultivation. China, Japan and South Korea in particular process imported cassava into bioethanol.

Cultivation in mixed crops

Cassava is very often grown together with other crops – especially on the African continent. In Thailand and Brazil, on the other hand, it is grown as a monoculture. Smallholder farms in Africa combine its cultivation with other crops. Typical combinations are maize, pulses and melons. In addition, cassava plays a role as an intermediate crop in the first years of tree or shrub crops such as coconut palms, cocoa or coffee, where both the production of food and, in some cases, the provision of shade for the young permanent crops are important. In Asia, too, there are various mixed cultures with cassava – often also with maize and pulses. In Vietnam, the combination with peanuts is popular.

Such mixed crop cultivation not only helps biodiversity and soil health, but also provides small farmers with a more reliable income: They can harvest and sell different crops at different times. Combined with as little tillage as possible and intensive mulching, cassava cultivation can be intensified sustainably.

Cassava on a plate and in a jar

The root tubers are mainly used as food, occasionally the leaves are also used as a vegetable. The tubers, which can be up to one meter long and 3 cm to 15 cm thick, can weigh up to ten kilograms. They are surrounded by a corked, usually reddish-brown outer layer; inside they are usually white, occasionally also yellow or reddish.

Cassava is eaten freshly baked and cooked or processed into flour. To make cassava flour in the traditional way, the tubers are peeled, ground or grated and then soaked. After a few days, the material is pressed, washed and roasted in ovens. In South America, cassava flour is used to make flatbread, sauces, soups or even alcoholic drinks, while in West and Central Africa the cassava porridge fufu is particularly popular.

A by-product of cassava flour production is starch, which is called tapioca and is produced by heating the moist starch to around 70 degrees. At this temperature, the starch gelatinises and becomes more easily soluble and digestible. Tapioca is sold in the form of balls or flakes. These can be found in puddings, porridges, wraps, bubble teas and desserts.

The young, protein-rich leaves of cassava are also an important vegetable in many countries and are eaten as well. In contrast to the leaves, however, the tubers contain only small amounts of protein, iron and zinc. This leads to deficiency symptoms in people who mainly eat cassava.

Sources

S. Rehm, G. Espig, 1984: Die Kulturpflanzen der Tropen und Subtropen
W. Franke, 1992: Crops of the Tropics and Subtropics
FAO (2013): Save and Grow: Cassava. A guide to sustainable production intensification. Link.
FAO (2000): The world cassava economy. Link.