Amorphophallus konjac
Devil's tongue
Overview
Amorphophallus konjac is a tuberous perennial in the Araceae grown from a flattened corm reaching 10 inches (25 cm) across and 9 pounds (4 kg) in weight on mature plants. Each season the corm produces a single leaf on a petiole 24-60 inches (60-150 cm) tall, pale green to olive with darker and paler mottling that resembles lichen on bark; the colouring varies between clones. The blade divides three times and spreads 24-48 inches (60-120 cm) across, carried horizontally. The inflorescence rises from the dormant corm in spring before the leaf, on a peduncle 8-24 inches (20-60 cm) tall. The spathe is dark maroon to purple, funnel-shaped, 8-22 inches (20-55 cm) long, with a wavy margin; the dark purple spadix extends beyond it, bringing the whole inflorescence to 20-44 inches (50-110 cm). The spadix warms above air temperature and releases a carrion odour for 24-36 hours. The plant is polycarpic and flowers in successive years once the corm passes about 2 pounds (1 kg). The corm is processed into konjac flour for noodles and gels. Raw tissue contains calcium oxalate crystals that irritate skin and mucous membranes. Corms rot if held wet and below 50 degrees F (10 degrees C) during dormancy.
Native Range
Native to subtropical and tropical eastern Asia, with wild populations recorded in Yunnan and Sichuan in southern China and in adjacent parts of northern Vietnam. Habitat is open forest, forest margins, and disturbed slopes between about 800 and 8,200 feet (250-2,500 m), with a dry season during which the corm rests. It has been cultivated for centuries in China, Japan, and Korea and is naturalised in parts of Southeast Asia.Suggested Uses
Grown in containers of 5-10 gallons (19-38 L) and in shaded borders in zones 7-10, at 24-36 inch (60-90 cm) spacing to allow for the leaf spread. Planted in aroid collections and subtropical bedding schemes for the mottled petiole and divided leaf. The corm is the source of konjac flour, used in shirataki noodles, konnyaku gel, and as a thickener, with commercial production centred on Japan and China.How to Identify
Appearance
Size & Dimensions
Height2' - 5'
Width/Spread2' - 4'
Bloom Information
The inflorescence opens in spring, from March to May under glass and from April to June outdoors in zones 7-9, ahead of any leaf. The spathe stays open 2-4 days. Odour is released during the first evening and the following morning, in two pulses lasting 6-12 hours each while the spadix warms. Corms under about 2 pounds (1 kg) produce a leaf and no inflorescence.
Detailed Descriptions
Flower Description
dark maroon to purple spathe with a dark purple spadixFoliage Description
green leaflets on a pale green to olive petiole mottled dark and lightGrowing Conditions
Sun Requirements
Requires 2-6 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Corms are planted 4-6 inches (10-15 cm) deep in a free-draining mix in spring once soil passes 60 degrees F (16 degrees C). Water is withheld until the shoot breaks the surface, then applied weekly through leaf growth; corms watered before the shoot appears rot. Light to moderate shade suits the leaf, and full midday sun scorches the blade above 90 degrees F (32 degrees C). Feeding every 2-3 weeks through the growing season with a balanced fertiliser raises corm weight by 50-200 percent in a season. Water is withdrawn as the leaf yellows in autumn, and corms are lifted and stored dry at 50-60 degrees F (10-16 degrees C) where winter ground temperatures fall below 50 degrees F (10 degrees C). In zones 7-9 corms overwinter in the ground under 4-6 inches (10-15 cm) of mulch on free-draining sites.Pruning
The leaf is left standing until it yellows and falls in autumn, since the corm draws reserves from it during senescence; leaves cut while green reduce corm weight for the next season. The collapsed petiole is cut at the corm surface once dry. Spent inflorescences are cut at the base after the spathe withers, unless seed is wanted. Offsets are detached from the parent corm during dormancy and grown on for 2-3 years to reach flowering size.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
fall
Container Growing
Suitable for container growing
Minimum container size: 5 gallons