Devil's Tongue, Devil's Tongue, Snake Plant, Konjac, Konnyaku Potato, Voodoo Lily

Amorphophallus konjac

Physical Characteristics

Amorphophallus konjac is an evergreen Perennial growing to 1.3 m (4ft 3in) by 1.3 m (4ft 3in) at a fast rate. See above for USDA hardiness. It is hardy to UK zone 8 and is frost tender. The flowers are pollinated by Flies. Suitable for: light (sandy) and medium (loamy) soils and prefers well-drained soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils and can grow in very acid soils. It can grow in full shade (deep woodland) or semi-shade (light woodland). It prefers moist soil.

Distribution

E. Asia - southwest China.

Habitats

Edible Uses

Edible Parts: Root Edible Uses: Corm - cooked[ 200 ]. The root must be thoroughly boiled or baked, it is acrid when raw (see notes above on 'Known Hazards'[ K ])[ 200 ]. Very large, it can be up to 30cm in diameter[ 266 ]. 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'[ 183 ]. Konnyaku is a type of flour valued for its use in many dietary products[ 266 ]. The flour is valued for its ability to clean the digestive tract without being a laxative[ 183 ]. A nutritional analysis is available[ 218 ]. This root is very high in water and low in calories, so it is being promoted as a diet food in N. America[ 218 ]. Especially just before the foliage declines prior to dormancy, the tubers are a rich source of mannan, a polysaccharide of mannose and glucose[ 472 ]. The mannose is extracted and widely used in foods for diabetics[ 472 ]. Glucomannan, a soluble fibre formed from mannan and glucose, cannot be metabolized by the human body, but is metabolized by intestinal bacteria. Inside the digestive system, glucomannan absorbs up to 200 times its weight in water without any negative action upon the digestive system. It therefore can give a feeling of fullness and be of use to aid in weight loss, it also relieves constipation and irritable bowel syndrome, as well as reducing serum cholesterol levels[ 472 ]. Glucomannan is widely used as an emulsifier and stabilizer in foods and drinks[ 472 ].

Medicinal Uses

The root is oxytocic and sialagogue[ 178 ]. It is used in the treatment of cancer[ 218 ]. Glucomannan, a soluble fibre obtained from the tuber, cannot be metabolized by the human body, but is metabolized by intestinal bacteria. Inside the digestive system, glucomannan absorbs up to 200 times its weight in water without any negative action upon the digestive system. It therefore can give a feeling of fullness and be of use to aid in weight loss, it also relieves constipation and irritable bowel syndrome, as well as reducing serum cholesterol levels[ 472 ]. The flowers are febrifuge[ 218 ].

Known Hazards

We have one report that this plant is very toxic raw, though no more details are given[ 178 ]. 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[ 238 ]. (Parts of plant are poisonous if ingested)