Alocasia macrorrhizos

Alocasia macrorrhizos is a species of flowering plant in the arum family (Araceae) that is native to rainforests of Maritime Southeast Asia, New Guinea, and the Murray Islands group in the Torres Strait. It has long been cultivated in South Asia, the Philippines, many Pacific islands, and elsewhere in the tropics, in the order of tens of thousands of years. Common names include giant taro, giant alocasia, ʻape, biga, and pia. In Australia it is known as the cunjevoi (a term which also refers to a marine animal).

Description

A very large herb. A taro family plant. It has a stout erect trunk up to 4 m tall. This has upright leaves which are arrow shaped. Leaves have round lobes at the bottom. The leaves are leathery and are often wavy around the edge. The secondary veins are not prominent. The leaf blade can be 1-1.2 m long. The leafy structure around the flower is yellow in the upper section. It forms a hood and drops off as the flower opens. The fruit are bright red berries. The corm is large, often curved and above the ground. It often has small cormels at the side. Brown trailing fibres of the leaf bases often hang from the stem. The leaves and petioles contain stinging crystals.

Edible Uses

The corm is edible when thoroughly cooked — cooking is necessary to destroy the calcium oxalate crystals it contains. The basal part of the stem, which can reach up to 1 metre tall and 20cm in diameter, is peeled and used as a cooked vegetable, suitable for adding to soups and stews. A very easily digested starch can also be extracted from the stem. In some cultivars, the leaves and stalks are edible as well.

Traditional Uses

The stems and corms are eaten after roasting or boiling. The main corm is cooked and eaten after being carefully peeled. The young leaves are edible. CAUTION The mouth can be irritated by chewing improperly cooked plant parts due to chemicals called oxalates. The stems are cut into small pieces and boiled and eaten in curries. The stems are boiled and the water thrown away. The starch is also extracted from the rootstocks. The young shoots are cooked and eaten. The harvested food can be stored for about one week.

Medicinal Uses

Giant taro is widely used in traditional medicine across the regions where it is grown as a food crop, with all parts of the plant employed. The stem sap is used to treat earache or boils in the ear, and applied externally to cuts. In New Guinea, the sap and leaves are used to treat headaches. The leaves are considered antimicrobial, antifungal, antioxidant, hepatoprotective, antidiarrheal, and antiprotozoal. The leaves and rhizome are used to treat impetigo, furunculosis, phlegmon, and snakebite — administered orally as a liquid extract, with the residue applied as a poultice. They are also used for colic and vomiting, in a daily dose of 10 to 20g of dried rhizome as a decoction. A plaster made from the rhizome is applied topically and is considered effective against furunculosis. Sexual insufficiency is treated by eating the leaves cooked in coconut milk. The roots are used for swollen lymph glands, and the wood for stomach-ache and diarrhoea. Leaves are collected throughout the year and used fresh; rhizomes are boiled to reduce itching compounds, then sun-dried or heat-dried.

Known Hazards

All parts of the plant contain calcium oxalate crystals. This substance is toxic fresh and, if eaten, makes the mouth, tongue and throat feel as if hundreds of small needles are digging in to them. However, calcium oxalate is easily broken down either by thoroughly cooking the plant or by fully drying it and, in either of these states, it is safe to eat the plant. People with a tendency to rheumatism, arthritis, gout, kidney stones and hyperacidity should take especial caution if including this plant in their diet.

Distribution

A tropical plant. It is widely distributed in open wetlands and along streams and in some types of humid forest. The plant grows wild from sea level up to 2600 m altitude in the tropics. Giant taro is a tropical plant and will not grow well below 10°C. It requires a well distributed rainfall and does not tolerate drought. Even though it grows along creek banks it cannot tolerate waterlogged soil. It is only used as food in a few coastal areas. Wild forms commonly seen growing are bitter and not used. It does not do well on atolls. It suits hardiness zones 11-12.

Where It Grows

Africa, American Samoa, Asia, Australia, Bangladesh, Bougainville, British Indian Ocean Terr., BIOT, Cambodia, Caroline Islands, Central America, Chuuk, Cook Islands, Cuba, Dominican Republic, East Timor, Easter Island, Ecuador, Fiji, French Polynesia, FSM, Guam, Guatemala, Guianas, Haiti, Hawaii, Himalayas, India, Indochina, Indonesia, Jamaica, Japan, Kiribati, Kosrae, Laos, Madagascar, Malaysia, Maldives, Marianas, Marquesas, Marshall Islands, Micronesia, Myanmar, Nauru, New Caledonia, Niue, Northeastern India, North America, Pacific, Pakistan, Palau, Papua New Guinea, PNG, Philippines, Pohnpei, Puerto Rico, Rotuma, Samoa, Sao Tome and Principe, SE Asia, Singapore, Solomon Islands, South America, Sri Lanka, St Helena, Suriname, Tahiti, Taiwan, Thailand, Timor-Leste, Tokelau, Tonga, Truk, Tuvalu, USA, Vanuatu, Vietnam, Wallis & Futuna, West Africa, West Indies, Yap,

Cultivation

The top of the main corm is planted. The small round cormels can be planted, but are slow to mature. A spacing of 1.2 x 1.2 m is suitable. Because the giant taro takes more than a year to be ready to harvest, it often ends up left growing in an old garden site without much care or weeding, until the owner wants to harvest it. The mouth can be irritated by chewing improperly cooked plant parts due to chemicals called oxalates. Giant taro contains small needle-like calcium oxalate crystals in the tissues. It is necessary to remove these during the preparation and cooking. The method of peeling is important. Normally some ladies who are especially experienced at peeling do this job. Also the taro corm is often left to wilt for a week after it is harvested and before it is used. Also to help remove some of the crystals, the stem is baked for a long time, or boiled in several changes of water. It is also important to use the right variety of giant taro because the kinds grown in gardens have less of the chemical than wild ones.

Propagation

Seed is best sown as soon as it is ripe and germinates best at 24°C. The rootstock can be divided as the plant comes into growth. Offsets appear at the base as the plant matures and can be easily transplanted.

Other Uses

The plant grows rapidly in wetland conditions and accumulates metal contaminants such as zinc, showing promise for use in sewerage treatment beds. A fibre is said to be obtainable from the plant. Giant taro is also noted for its role in carbon farming and food forest systems.

Production

Corms of 8.5 to 40 kg have been harvested from individual plants of unknown age. The time to maturity is about 12 months but plants are often left for 2-3 years.

Other Information

It is a commercially cultivated vegetable. This taro is of local importance only in some coastal areas and islands of Papua New Guinea e.g. Rabaul, Namatanai. It is important in several Pacific Islands and Sri Lanka.

Notes

There are about 60-70 Alocasia species.

Nutrition

Synonyms

Also Known As

Abis, Alu, Ape, 'Apea mamala, Babai, Bada gadri, Biga, Birah negeri, Birah, Bisech, Boafuredhdhe, Chara kanda, Conjevoi, Daun keladi, Desa-ala, Dhopa, Dranu, Elephant Ear, Fale, Fine, Gabi, Habarala, Hai yu, Henchala, Hensoksu, Honggu, Ka, Kadard, Kansalu, Kape, Karkalo, Kebei, Khajarikochai, Kiri ala, Kiri habarala, Kradat daeng, Lai, Maanaka, Mahuya-pein, Man kachu, Man kanda, Man kochu, Manaka, Mana saru, Mana thaso, Mankachu, Mankanda, Mankochu Marambu, Merukankilangu, Ohd, Oht, Onak, Pai, Papao-alaka, Papao-atolong, Papa sisa, Parum sembu, Pein-gyi, Piga, Puna, Qos tsov, Rata-ala, Sankhasaru, Saombia, Sente, Spoon Lily, Ta'amu, Tamu, Te kabe, Thagong, Totoa taco, Via, Via dalo, Via mila, Wod, Wot, Wut

References (158)

• Giant taro references
• Aberoumand, A. and Deokule, S. S., 2009, Determination of Elements Profile of Some Wild Edible Plants. Food Anal. Methods. 2:116-119 (As Alocasia indica)
• Allen, R.N., 1929, Photomicrographs of Philippine starches. Philipp. J.Sci., 38(2), 247.
• Ambasta S.P. (Ed.), 2000, The Useful Plants of India. CSIR India. p 29 (As Alocasia indica)
• Anderson, E. F., 1993, Plants and people of the Golden Triangle. Dioscorides Press. p 20

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