Amorphophallus konjac aka Devil's Tongue

Amorphophallus konjac is a perennial in the arum family. Common names include konjac, devil's tongue, and snake palm. Kew places its native range in Yunnan, China. It grows at forest edges and in shady thickets. Growers in China and Japan raise it for food. It also grows as an ornamental across eastern Asia.

Garden plants reach about 3–5 feet [1–1.5 metres] tall and wide. A round, brown corm stores food beneath the soil. Large corms can reach 1 foot [0.3 metres] across. Each plant sends up one large, divided leaf each year. Its bright green leaflets form a broad, branching canopy. The leaf can reach 3.3 feet [1 metre] long. Its thick stalk may be pink or green with pale marks. The plant sheds its leaf before its winter rest. Offsets grow from the corm and can form a clump.

Mature corms bloom before the new leaf opens. Sources report spring blooms, though RHS gives summer. The flower head stands 3–4 feet [0.9–1.2 metres] tall. A dark red-purple spathe surrounds the tall, brown spadix. Tiny male and female flowers grow on the spadix. The spathe has a rippled edge and a glossy surface. The spadix warms up and gives off a foul smell. This draws carrion flies and midges, which pollinate it. The smell fades after pollination but can overwhelm an indoor space.

Grow it in filtered light with shelter from hot afternoon sun. Use rich, moist loam that drains well; avoid clay. Water and feed during growth, then reduce water in winter. RHS advises warm storage with the compost kept barely moist. Frost harms the leaf and flower, though the corm tolerates more cold. US sources list hardiness from USDA zone 6 upward. RHS rates it H1B for UK conditions. It suits large pots, greenhouses, and mixed borders. Its bold leaf makes a strong garden accent. It needs no pruning and has few reported pest or disease problems.

The corm supplies starch for noodles, tofu, and konnyaku gel. Food makers also use it to thicken foods and drinks. Raw corms are toxic and need thorough cooking before eating. Calcium oxalate crystals can cause pain in the mouth and throat. RHS warns of harm to people and pets. It also warns of skin and eye irritation when handling. The plant has traditional medicinal uses in Asia.