Konjac (devil’s tongue) Amorphophallus konjac
Konjac (devil’s tongue) (Amorphophallus konjac) is a deciduous perennial vegetable in the Araceae family, native to Yunnan, south-west China, and northern Indochina. It grows 80 cm–1.5 m (31 in–4.9 ft) tall and 80 cm–1.2 m (31 in–3.9 ft) wide, wants part sun to part shade and moderate water, and is hardy to about -8 °C (18 °F). Space plants about 80 cm (31 in) apart.
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Konjac (devil’s tongue) at a glance
| Type | Perennial vegetable, deciduous |
|---|---|
| Family | Araceae |
| Mature height | 80 cm–1.5 m (31 in–4.9 ft) |
| Mature spread | 80 cm–1.2 m (31 in–3.9 ft) |
| Spacing | 80 cm (31 in) centre to centre |
| Sun | Part sun to part shade, at least 3 h of direct sun a day |
| Water | Moderate; drought tolerance low, waterlogging tolerance none |
| Soil pH | 6–7.5 |
| Cold hardiness | About -8 °C (18 °F) once established (roughly USDA zone 8) |
| Heat stress | Likely above about 34 °C (93 °F) |
| Flowering | about 156–261 weeks after planting, for 1–1 weeks |
| Wind tolerance | None |
| Pollinator value | Low |
| Edible | Yes: corm (processed into konjac flour, konnyaku and shirataki noodles) |
| Native to | Yunnan, south-west China, and northern Indochina |
| Common in gardens of | 🇨🇳 China, 🇯🇵 Japan, 🇰🇷 South Korea, 🇻🇳 Vietnam, 🇹🇭 Thailand, 🇬🇧 United Kingdom, 🇺🇸 United States |
Is Konjac (devil’s tongue) toxic?
- People: moderately toxic
- Cats: moderately toxic
- Dogs: moderately toxic
- Parts: raw corm, all parts
The raw corm is full of calcium oxalate crystals and must be processed with alkali before eating. Jelly sweets made from konjac have caused choking deaths and are banned in mini-cup form in the EU.
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with Konjac (devil’s tongue)
No well-documented helpful pairing. Group it with plants that like part sun to part shade and moderate water.
Questions about Konjac (devil’s tongue)
- How far apart should I plant Konjac (devil’s tongue)?
- About 80 cm (31 in) apart, centre to centre. A mature plant spreads 80 cm–1.2 m (31 in–3.9 ft).
- Does Konjac (devil’s tongue) need full sun?
- Part sun to part shade: at least 3 hours of direct sun a day.
- How much water does Konjac (devil’s tongue) need?
- Moderate water. Drought tolerance is low and waterlogging tolerance none.
- How cold-hardy is Konjac (devil’s tongue)?
- It tolerates about -8 °C (18 °F) once established, roughly USDA zone 8.
- When does Konjac (devil’s tongue) flower?
- About 156–261 weeks after planting, for 1–1 weeks.
- Is Konjac (devil’s tongue) poisonous to cats and dogs?
- For cats it is moderately toxic; for dogs moderately toxic; for people moderately toxic. The raw corm is full of calcium oxalate crystals and must be processed with alkali before eating. Jelly sweets made from konjac have caused choking deaths and are banned in mini-cup form in the EU.
- What grows well with Konjac (devil’s tongue)?
- There is no well-documented companion pairing for Konjac (devil’s tongue). Group it with plants that like the same sun (part sun to part shade) and water (moderate).
Sources and evidence
Evidence grade A (A: strong evidence).
- Plants of the World Online (taxonomy, native range), Royal Botanic Gardens, Kew
- Flora of China, Missouri Botanical Garden & Harvard University Herbaria (eFloras)
- GRIN-Global Taxonomy, USDA ARS
Notes and assumptions
- From a big round corm comes a single umbrella-like leaf on a mottled stem, and in some springs, before the leaf, a tall maroon spathe that smells of rotting meat for a day or two. The corm is farmed in China and Japan for glucomannan flour, made into konnyaku jelly and shirataki noodles. Corms survive frost in dry soil.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
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