Common Name: Cassava

General Information

Manihot esculenta is a shrub growing around 3 metres tall.
One of the most important of the cultivated tropical food crops, there is evidence that it was being cultivated for its leaves and corms in Peru 4,000 years ago[]. Its cultivation gradually spread and now it is widely grown in tropical areas throughout the world, especially in lowland tropical regions[, ].

Known Hazards

The leaves contain the harmful glucoside linamarin, which can release the toxic hydrocyanic acid in the presence of the enzyme linase[, ]. This can be destroyed by heat[]

Botanical References

Range

Tropics.

Habitat

Widely cultivated as a food crop, it is not known in a truly wild situation.

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Shrub
Height	3.00 m
Pollinators	Insects
Cultivation Status	Cultivated

Cultivation Details

Cassava grows best at elevations below 1,700 metres[]. Plants do not grow well at temperatures lower than 16°c, the stems and leaves are very sensitive to even short periods of chilling[]. Temperatures in excess of 29°c may have an adverse effect on growth and development[]. Plants grow best in areas where rainfall is in the range of 500 - 2,500mm per annum[]. A short-day plant, tuber production is reduced in daylengths greater than 12 hours[].
Plants need some shelter from bright sunshine or their leaves can be burnt[]. A quite tolerant plant, succeeding in drier and moister soils as well as in quite deep shade[]. Cassava is not a particularly greedy plant, though yields are improved if they are well fed[]. A sandy or sandy loam is generally preferred for growing the plant[]. Requires a well-drained soil[]. Some cultivars are extremely drought resistant[]. Tolerates a pH in the range 5.5 - 8.0[].
The plant grows, and can be harvested, all year round[]. The roots take about six months to mature, so it is possible to grow two crops a year[]. The roots are often badly damaged by termites[].
There are many named varieties. There are two groups of cultivars, the sweet and the bitter[]. Sweet forms contain much less hydrocyanic acid, and this is confined mainly to the outer phellodern layers of the root tuber[]. In bitter varieties the hydrocyanic acid is widely distributed throughout the tuber[].
Care must be taken to grow the cultivated 'sweet' varieties that have been developed as food crops - ornamental, usually variegated, forms are usually bitter tasting and poisonous[].
The leaves are particularly susceptible to damage by insecticide sprays[].
Cassava will usually grow into a tall spindly bush unless cut back - they are very tolerant of heavy harvesting and so in cultivation it is best to keep them at about 1 metre tall[].

Edible Uses

Young leaves - cooked as a vegetable[]. Boiled like spinach, or added to stews[]. The leaves need to be boiled for about 15 minutes in order to destroy harmful glucosides[]. Some sweet varieties contain little or no glucosides[].

Root - cooked and used as a vegetable[]. The tuberous root can be sliced and fried like chips, boiled and added to vegetable dishes, or made into a flour and used in breads and biscuits, or as a thickener in gravies, soups, desserts etc[]. The root is higher in carbohydrate and rather deficient in protein than many other root crops[]. Unfortunately, where cassava is used as the main staple in the diet, it can lead to malnutrition[]. It is a fairly good source of vitamin C[].Starch from the tuber is used to make tapioca[, ]. Some care should be exercised in using this plant for food since it is more or less poisonous when raw. Sweet varieties need to be simmered for 10 minutes before eating, whilst bitter varieties should be soaked for 24 hours prior to simmering for at least 10 minutes in fresh water[].

Medicinal

Cassava is often used in traditional medicine and has a number of applications[].
The plant is antifungal, antiviral, mutagenic and antibacterial[, ].

The roots of bitter varieties can be used to treat scabies, diarrhoea and dysentery[]. The juice of the grated tubers is used to treat constipation and indigestion[].
A flour made from the roots can be used as a dusting powder on the skin in order to help dry weeping skin[]. Soaked with Carapa oil, it is used as a poultice on shattered muscles[]. It is mixed with rum and rubbed onto children's skin as a treatment for abscesses and skin eruptions[]. It can be made into an ointment to treat fungal dermatitis[].

The leaves are haemostatic[]. They are made into a poultice to treat wounds[]. The leaves are infused in bath water to treat influenza and fevers[]. The leaves are heated and rubbed across sore eyes[].

The stem is folded and rubbed across the eyes of people suffering from glaucoma[].

The bark of the plant, together with that of Cordyline terminalis, is thought to prolong life[].

Sugar cane and annatto are employed in an antidote to ingested water which has been poisoned by the soaking roots of this plant[].

Other Uses

Insect repellent - a mulch of the leaves and stems repels root knot nematodes[].

A glue can be made from the starch[]. It is used on postage stamps[].

The starch in the root is used as a size for cotton fabrics[].

Propagation

Seed - seedlings are very unlikely to be true to type and could possibly revert to bitter types.
Cuttings - they root easily[]. Take shoots about 30cm long and 15mm thick from a woody part of the stem and remove all leaves. It is possible to root the shoots by standing them in a container of water, planting them out when they have made good roots. Alternatively, plant the cuttings out directly in the soil making sure that they are kept moist[].

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