Amorphophallus rivieri

Durieu.

Devil's Tongue, Umbrella Arum, Leopard Palm, Snake Palm

AsparagaceaeRootsPotential hazards — see below

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What to Eat

Edible parts: Root

Rhizome - cooked. The root must be thoroughly boiled or baked, it is acrid when raw. Very large, it can be up to 30cm in iameter. In Japan the large brown tubers are peeled, cooked and pounded to extract their starch, which is solidified with dissolved limestone into an edible gel called 'Konnyaku'. Konnyaku is a type of flour valued for its use in many dietary products. The flour is valued for its ability to clean the digestive tract without being a laxative. A nutritional analysis is available. This root is very high in water and low in calories, so it is being promoted as a diet food in N. America.

Known Hazards

We have one report that this plant is very toxic raw, though no more details are given. It belongs to a family where most of the members 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.

Where to Find It

E. Asia - Cochin China, East Indies.

TEMPERATE ASIA: China (Yunnan Sheng) TROPICAL ASIA: Vietnam

How to Identify

Amorphophallus rivieri is a PERENNIAL growing to 0.8 m (2ft 7in) by 0.6 m (2ft). See above for USDA hardiness. It is hardy to UK zone 10 and is frost tender. The species is monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and is pollinated by Flies. Suitable for: light (sandy) and medium (loamy) soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist soil.

How to Grow

Requires shade and a rich soil in its native habitats, but it probably requires a position with at least moderate sun in Britain. This species is being increasingly cultivated for its edible tubers in Japan and China The plants are not winter hardy outdoors in Britain but are sometimes grown outdoors in this country as part of a sub-tropical bedding display. It is also said to make a good house plant. The tuber is harvested in the autumn after top growth has been cut back by frost and it must be kept quite dry and frost-free over winter. It is then potted up in a warm greenhouse in spring ready to be planted out after the last expected frosts. The tubers are planted 15cm deep. The plant has one enormous leaf and one spadix annually. It requires hand pollination in Britain. When ripe for pollination, the flowers have a foetid smell to attract carrion flies and midges. This smell disappears once the flower has been pollinated.

Propagation: Seed - best sown in a pot in a warm greenhouse as soon as it is ripe and the pot sealed in a plastic bag to retain moisture. It usually germinates in 1 - 8 months at 24°c. When large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for at least a couple of years. Plant them out in late spring or early summer, after the last expected frosts, and give them some protection such as a cloche until they are growing away strongly. Division of offsets. These are rarely produced.