Cocoyams are herbaceous perennial plants belonging to the family Araceae and are grown primarily for their edible roots, although all parts of the plant are edible. Cocoyams that are cultivated as food crops belong to either the genus Colocasia or the genus Xanthosoma and are generally comprised of a large spherical corm (swollen underground storage stem), from which a few large leaves emerge. The petioles of the leaves stand erect and can reach lengths in excess of 1 m (3.3 ft). The leaf blades are large and heart-shaped and can reach 50 cm (15.8 in) in length. The corm produces lateral buds which give rise to tubers or cormels and suckers or stolons. Cocoyams commonly reach in excess of 1 m (3.3 ft) in height and although they are perennials, they are often grown as annuals, harvested after one season. Colocasia species may also be referred to as taro, old cocoyam, arrowroot, eddoe, macabo or dasheen and originates from Southeast or Central Asia. Xanthosoma species may be referred to as tannia, yautia, new cocoyam or Chinese taro and originates from Central and South America.
Young taro plants in French Polynesia
Aerial view of taro fields in French Polynesia
Taro leaf close-up
Mature cocoyam roots for sale at a market in Nigeria
Cocoyam is most commonly grown for its starchy edible roots. Colocasia is grown for its corm which is consumed after boiling, frying or roasting. The corms can be dried and used to make flour or sliced and fried to make chips. The leaves of the plant are also edible and are usually consumed as a vegetable after cooking in dishes such as stews. Xanthosoma species produce tubers much like potato and are boiled, baked, steamed or fried prior to consumption. The corm of some varieties is also consumed. Young leaves are eaten as a vegetable.
Cocoyam grows best in fertile, well-draining, sandy loam soil with a pH between 4.2–7.5.It can be grown in a wide variety of conditions including paddies in wetland areas using a system similar to that of rice. Xanthosoma species require temperatures above 21°C (69.8°F) to grow properly. Unlike Colocasia spp, they will not tolerate waterlogging and grow best in deep, well-draining loams with a pH between 5.5 and 6.5 in partial shade. Cocoyam will thrive when planted in full sunlight or partial shade. The plants can survive for short periods at temperatures of 10°C (50°F) but will be damaged or killed by lower temperatures.
Cocoyam is vegetatively propagated from headsetts (“tops”) or suckers which establish quickly and give the highest rate of survival. Larger headsetts and suckers tend to produce larger corms and bigger yeilds but the size of the planting material may be determined by the particular cultivar being grown e.g. some varieties will produce two heads from the same corm if the sucker that is planted is too big and therefore medium sized suckers are selected when growing tubers for export. Headsetts and suckers should only be taken from healthy plants in order to protect yields and prevent the spread of diseases.
Cocoyam is planted in such a way as to encourage sucker growth e.g. the use of larger plant spacing and shallow planting depths. The planting material (sucker or headsett) is set in furrows or ridges and plant spacing can be anywhere between 30 to 100 cm (11.8–39.4 in) between plants depending on the prevailing soil and climatic conditions. A narrow spacing helps to control weeds whereas a wider spacing is preferred for good growth.
Cocoyam plantation in Cameroon