Alocasia macrorrhizos aka Giant Taro

Alocasia macrorrhizos is also called giant taro. It belongs to the arum family. Its native range spans central Malesia to Queensland, Australia. It grows in wet parts of the tropics. These include damp ground near rivers. People grow it for food and for its large leaves. It has also spread beyond gardens in many tropical areas.

This plant stays green and lives for more than one year. It grows upright from rhizomes, which are stems below ground. Garden plants reach about 5–8 feet [1.5–2.5 metres] tall and wide. Reports from the tropics give heights of 13 feet [4 metres]. Some plants reach 16 feet [5 metres]. Thick stems hold large, glossy green leaves. Pale green veins stand out against the leaf blades. The RHS gives leaf lengths of 4 feet [1.2 metres]. Chicago Botanic Garden reports leaves of up to 6 feet [1.8 metres]. The leaves point upward, and their edges have rounded curves. Long leaf stalks help give the plant its bold shape.

Pale green flowers may appear in summer. The plant flowers on a seasonal basis. Missouri Botanical Garden calls the flowers greenish-white and showy. It also notes that the fruit adds visual interest. Insects carry pollen between the flowers. The leaves remain the main reason to grow this plant. It suits beds with shelter and courtyards. It also suits pots and warm glasshouses. In cold regions, gardeners can bring potted plants indoors for winter.

Give it part shade outdoors. Indoors, give it bright light out of direct sun. It needs moist soil that drains well and humid air. Sandy soil and loam both suit it. It accepts acid, neutral, or alkaline soil. Water well during growth, then cut back in winter. The RHS advises keeping indoor plants above 59°F [15°C]. Feed every two to three weeks from spring through autumn. It can grow fast in summer with a steady water supply. Sources list USDA zones 9–11 and UK hardiness H1A. You need not prune it as part of routine care. Divide rhizomes in spring or sow fresh seed. Watch for mites, mealybugs, scale, and aphids. The RHS reports few disease problems.

Raw plant parts contain calcium oxalate crystals and are toxic. Eating them can cause pain in the mouth and throat. The plant also poses risks to pets. Contact can irritate skin and eyes. Wear gloves when handling it. People eat the corm and lower stem as cooked foods. Cook them well for a long time before eating. Sources record uses in folk medicine. These uses do not show that the plant is safe. Other reported uses include fibre. Reports also suggest possible use in treating wastewater.