Common Name: Giant Taro

General Information

Alocasia macrorrhizos is a large, evergreen, herbaceous perennial plant, usually growing 2 - 4 metres tall, occasionally to 5 metres. It has thickened stems that can be 3 metres or more in height and 20cm in diameter, topped with leaves up to 1 metre long[].
The plant is cultivated in some parts of lowland tropical Asia, mainly for the edible stems but also for the corm[]. It is sometimes grown as an ornamental, valued especially for its large leaves and inflorescence.

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[].

Botanical References

Range

E. Asia - Indian subcontinent, Malaysia, widely naturalized in many other tropical and subtropical areas.

Habitat

Common along river banks and other damp places from sea-level to 500 metres[]. Cultivated lands, waste places, old gardens, mesic valleys, low moist disturbed and secondary forests, along riverbanks and streams from sea level to 800 metres[].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Perennial
Height	3.00 m
Pollinators	Insects
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Alocasia macrorrhizos is a plant of the higher-rainfall areas of the lowland tropics, where it is cultivated at elevations up to 1,000 metres. It grows best in areas where annual daytime temperatures are within the range 20 - 25°c, but can tolerate 10 - 32°c[].It prefers a mean annual rainfall in the range 2,500 - 3,500mm, but tolerates 2,000 - 4,200mm[].
Grows best in a position in some shade, but tolerant of full sun and of deep shade[, ]. Prefers a well-drained, humus-rich, fertile loam, though it is tolerant of a wide range of soil types from sands to heavy clays[, ]. Dislikes water-logged soils[]. Plants can tolerate a dry season of up to 4 months[]. Prefers a pH in the range 5.7 - 6.3, tolerating 5 - 7.3[].
Alocasia macrorrhizos has been intentionally introduced in many tropical and subtropical regions to be used as an ornamental and a food crop. It has the capability to reproductive sexually by seeds and vegetatively by corms, tubers, and root suckers, and it is able grow in a great variety of substrates and habitats ranging from full sun to deep shaded areas. It is listed as invasive in Cuba, New Zealand, and several islands in the Pacific, and it is considered to be a weed in Vietnam[]
Plants take from 400 - 600 days to mature, but the stems can then remain in a suitable condition for a considerable time[].
Whilst many forms of this plant contain calcium oxalate crystals (see notes above on toxicity), cultivars have been developed in India that do not contain oxalates[].
Like many species in the family Araceae, this plant has the ability to heat the flowering spadix as the pollen becomes ready for fertilization. This heat greatly increases the strength of the aroma released by the plant, thus attracting more pollinating insects. It can also have the effect of making the insects more active, thus increasing the level of fertilization[].

Edible Uses

Corm - cooked[]. The corm needs to be thoroughly cooked before being eaten in order to destroy the calcium oxalate crystals[, ]. When prepared for consumption in Guam, a stick is thrust into the tuber to avoid touching the plant - the tuber is then peeled, sliced, soaked and boiled with coconut milk in order to produce an edible starch food[],.

Stems - cooked[]. The basal part of the stem, which can be up to 1 metre tall and 20cm in diameter, is peeled and used as a cooked vegetable[, ]. It can be added to soups and stews[]. A very easily digested starch can be obtained from the stem[, ].

The leaves and stalks of some cultivars are edible[].

Medicinal

Giant taro is often used in traditional medicine in regions where the plant is cultivated as a food crop. All parts of the plant are used[, ].

The sap of the stem is used to treat earache or boils in the ear[]. Applied externally, it is used to treat cuts[]. In New Guinea, headaches are treated with the sap and the leaves[].

The leaves are said to be antimicrobial, antifungal, antioxidant, hepatoprotective, antidiarrheal, and antiprotozoal.
The leaves and the rhizome are used in the treatment of impetigo, furunculosis, phlegmon and snake·bite in the form of a liquid extract for administration by mouth, and their residue is used for poulticing. They are also used in treating colic and vomiting, in a daily dose of 10 to 20g of dried rhizome in the form of a decoction[].
The rhizome is used to make a plaster that is aplied topically and is said to be effective against furunculosis[].
Sexual insufficiency is treated by eating the leaves cooked in coconut milk[].

The roots are used to treat swollen lymph glands[].

The wood is used to treat stomach-ache and diarrhoea[].

The leaves and rhizomes are collected throughout the year. The leaves are used fresh. The rhizomes are boiled hard to reduce itching compounds, then sun·dried or heat·dried[].

Agroforestry Uses:

The plant grows rapidly in wetland conditions and has a propensity to accumulate metal contaminants such as zinc. It shows promise for use in sewerage treatment beds[].

Other Uses

A fibre is said to be obtained from the plant[].

Propagation

Seed - best sown as soon as it is ripe. Germinates best at 24c.
Division of the rootstock as the plant is coming into growth.

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