|Manihot subsp. var.|
|Standard Cyclopedia of Horticulture|
Manihot (native Brazilian name). Euphorbiaceae. Tropical trees and shrubs cultivated as ornamentals and for important economic products.
Usually glaucous and glabrous or nearly so: juice milky: lvs. alternate, entire to lobed or sometimes almost palmate: fls. large for the family, monoecious, in terminal or axillary racemes or panicles, apetalous; sepals united, at least at the base, imbricate, often petaloid; stamens 10; ovules 1 in each of the 3 cells; seeds carunculate.—About 130 species, all American and mostly in Brazil. Related to Jatropha and Ricinus. Although the plan of the infl. is different, several species of Manihot and Jatropha are otherwise so similar that they have been placed first in one genus and then in the other. Monogr. by Pax, in Engler's Pflanzenreich, hft. 44 (1910).
The cassava plant, M. utilissima, has been cultivated as a food plant since prehistoric times by the natives of Brazil. There are many varieties in cultivation and these are not known in the wild state. The plant is a perennial shrub in the tropics, and resembles somewhat the castor bean. The abundant starch in the large fleshy roots which grow in a cluster at the base of the stem gives it its food value. It is used in various ways as food, including the manufacture of tapioca, Brazilian arrow-root, and the like.
The roots contain more or less hydrocyanic acid which is often sufficient to render them deadly poisonous in the raw state. It is rendered harmless by heating or is pressed out with the juice in preparing the roots for food. The more poisonous varieties are generally known as bitter cassava, those with less of the acid as sweet cassava, but the amount of the poison varies with seasons and other conditions. Varieties of M. dulcis var. Aipi are also grown as sweet cassava in the tropics but are generally not very productive. M. carthaginensis is also sometimes used as cassava.
Cassava is grown in some of the warmer parts of the United States chiefly as a stock feed. It does best in light, but rich sandy soil. It is propagated by cuttings. Just before frost the more mature parts of the canes are cut and buried till spring and then cut into 4- to 6-inch pieces and planted 4 foot each way. The cultivation is similar to corn. In tropical countries the cuttings may be made and planted at any time. Some varieties, especially early maturing ones, may be grown from seed. The roots are left in the ground till used, as they decay quickly when harvested. The yield is from six to ten tons of roots to an acre, or even more. For further information on cassava, see "Cyclopedia of Agriculture," Vol. II, p. 227, and Farmers’ Bulletin, United States Department of Agriculture, No. 167.
Manihot Glaziovii and other species have long been utilized for rubber in the wild state in Brazil. Some years ago this species was planted extensively in various tropical lands out of its natural habitat, the general result being a low yield of rubber and disastrous failure of the enterprise. In recent years, plantations under proper conditions have given much better results. This is the chief source of the ceara rubber, so called from the town of Ceara in Brazil. Other species are also worked for rubber in the native woods of Brazil. M. dichotoma and M. piauhyensis are also being grown in rubber plantations with success. All the ceara rubber species grow in dry situations with little summer rainfall. M. piauhyensis is more shrubby and adapted to light sandy land and M. dichotoma to rough heavier soil. M. heptaphylla is also grown to some extent for rubber on light soil.
The ceara rubber trees are grown from seed, but may be raised from cuttings. The seed is planted about 1 inch deep in good soil and kept moist till the seedlings are well established. The germination is slow and irregular, taking from three weeks to six months. Filing the seed-coat to hasten germination has been tried but often encourages decay. The young plants are cut back and transplanted into the field after the stem has hardened. They grow rapidly, the taller species like M. Glaziovii, reaching 16 feet in ten months. The smaller ones may yield a full crop in four years after planting. (See Ule. Notizbl. Bot. Garden, Berlin, 5, 1908.)
Some species of manihot are occasionally grown in greenhouses mostly for the tropical effect of the foliage. They are grown in light but rich soil and do best in a dry room. They are propagated easily from seeds but are usually grown from cuttings of young but firm wood in sandy peat under glass with bottom heat.
Pests and diseases
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963