How To Grow And Care For Konjac

What you need to know about konjac

Devil’s tongue is the commonly used name for the konjac plant, which is related to the titan arum (Amorphophallus titanum), the world’s largest (and smelliest!) flower. It is grown for its starchy tubers, which are used in Japanese and Chinese cuisine. Tuber to 30cm in diameter; single leaf to 1.3m across and 60–75cm tall.
– Climate: sub-tropical to tropical; indoor plant in temperate or cooler areas.
– Soil: rich loam that drains well; quality premium potting mix in pots.
– Position: full sun or good ambient light; protection from winds (brittle stem).
– Feeding: use a long-term controlled-release fertiliser.
– Watering: keep consistently moist from the time the leaf shoot appears until it dies down in autumn.


Appearance and characteristics of devil’s tongue

Native to warm sub-tropical and tropical areas of eastern Asia, konjac grows from a large tuber up to 25cm or more across. In spring, it grows a single sturdy leaf stalk that opens out into three sections, creating an umbrella effect spanning more than a metre.
Like the titan arum, konjac flowers very rarely, but when it does, the flower will appear in late winter, before the leaf. The flower is very large, lily-like, deep maroon to purple-brown, and smells like rotting flesh to attract pollinating insects. If the smell really offends you, cut it off!

Dark red flowers, lily flower with pungent odour

Uses for devil’s tongue

Devil’s tongue is grown in many Asian countries for its tubers, from which a flour and a jelly or setting agent are made. Konjac flour is often substituted for gelatine in vegan diets. The flour, konnyaku in Japanese, is used in noodles known as shirataki and dishes such as oden. It has very little taste and is valued more for its texture and thickening than its flavour. It may also be made into yam cakes. Konjac is also used to make bath sponges that are very soft on the skin.

Some uses of konjac

How to grow devil’s tongue

Planting konjac

Devil’s tongue is grown from tubers and offsets or “pups” that develop around the outside of the parent tuber. Young tubers may be available to buy in winter while they are dormant (without leaves).
Konjac’s spreading root system grows from the neck, rather than the base of the tuber, so make sure to plant deeply to provide some stability for the plant—at least the tuber’s width below soil level. For example, if a tuber is 15cm wide, then it should be covered by at least 15cm of soil or potting mix.

Devil’s tongue is grown from tubers

Caring for devil’s tongue


Konjac needs to be kept consistently moist from the time the leaf or flower shoot starts to emerge until the leaf dies off in autumn. Stop watering as soon as the leaf starts to brown in autumn and, if possible, lie the pot on its side to keep it completely dry.


Devil’s tongue is a heavy feeder, so it’s important to fertilise it well through the growing period to keep it healthy and vigorous. Fortnightly boosts of liquid or water-soluble fertiliser from early spring until the leaf starts to die off in autumn will keep it growing strongly.


Harvest Konjac

The konjac plant can grow in various environments. The natural habitat for konjac is on mountainous regions 2000 to 4000 ft above sea level. In the best environment, the root of a konjac plant can grow to 1 to 2 pound in three years’ time. In less suitable environments and in the wild, it takes 6 to 8 years for the root to grow to half the size. Once the konjac root fully matures in the autumn of the third year, the plant is harvested after the plant withers away. Any plant that has not reach maturity is replanted in the next spring.

Harvest Konjac

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