Manihot esculenta Seeds | Cassava
LATIN NAME: Manihot esculenta
COMMON NAME: Cassava
Plant Profile
Cassava is a woody shrub of one to three metres with palmate leaves and a cluster of starchy roots at the base, each one a swollen section of the root system rather than a tuber. It is grown from stem cuttings, not from seed, in almost every case.
It is the fourth largest source of calories in the tropics, behind rice, maize and sugar cane, and it is the staple of the Congo basin and of much of north-east Brazil. The plant came from South America and crossed the Atlantic in the sixteenth century, and the Portuguese carried it to Africa and to Asia.
Science & Biotechnology
Cassava produces cyanogenic glucosides, linamarin and lotaustralin, which break down to hydrogen cyanide when the tissue is crushed. Bitter varieties hold enough to be dangerous and sweet varieties hold little, and the difference is measured rather than guessed. Processing, whether by soaking, grating, fermenting or cooking, removes most of the cyanide.
The crop is propagated by cuttings because seed is heterozygous and the plant is highly heterozygous in the field. Breeding programmes use seed for crossing and then fix the best lines by vegetative multiplication, and the current work concentrates on resistance to cassava mosaic disease and to brown streak, both of which can halve a harvest. The crop also responds to short days with tuber initiation, and day length is one reason yields differ so much between latitudes.
Uses & Benefits
The roots are boiled and eaten, or grated, pressed and dried into flour for farofa and for the flatbread of the Amazon. In Africa the root is pounded into fufu and the leaves are cooked as a green, and in Asia it goes into tapioca starch, which is used in food and in industry.
The starch is also fermented for ethanol and for biodegradable plastics, and the peel and the pomace are fed to livestock. Cassava is a famine-risk crop as well as a staple: it can be left in the ground for two years and dug when needed, which is why it is planted where the harvest of other crops is uncertain.
Growing from Seed
Take cuttings of twenty centimetres from a stem of ten months, with at least five nodes, and plant them at an angle with two thirds buried. Cuttings root within two weeks in moist soil, and the plant is ready to lift in nine to twelve months, or later if it is to be held in the ground.
Cassava needs sun, drainage and a free root run, and it yields poorly in heavy, wet soil, where the roots rot. Do not plant it where the ground has grown cassava for two seasons running, since root rot builds up. In a frost-free garden a single plant will supply a household for a month.
Our Take
The most important root crop of the tropics, and a plant that will sit in the ground until it is wanted. Never eat it raw, and never guess whether a variety is bitter.
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