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. Other common names include voodoo lily and elephant yam. It is grown for its starchy tubers, which are used in Japanese and Chinese cuisine.
I. Appearance and Characteristics
Konjac (or konjak, KON-yak, KON-jak) and konnyaku are common names of Amorphophallus konjac, a vegetable species native to Yunnan in southwest China which has an edible corm. It is also known as konjaku, konnyaku potato, devil’s tongue, voodoo lily, snake palm, or elephant yam (though this name is also used for A. paeoniifolius).
It is cultivated in warm subtropical to tropical areas of East and Southeast Asia, from China and Japan south to Indonesia and Vietnam (USDA hardiness zone 6–11). It is a perennial plant, growing from a large corm up to 25 cm (10 in) in diameter. The single leaf is up to 1.3 m (4 ft) across, bipinnate, and divided into numerous leaflets. The flowers are produced on a spathe enclosed by a dark purple spadix up to 55 cm (22 in) long.
Konjac is grown in East and Southeast Asia and it is prized for its large starchy corms, used to create a flour and jelly of the same name. It is also used as a vegan substitute for gelatin.
In Japan, over 90% of all domestically produced konjac is made in Gunma Prefecture.
II. How to Grow and Care
Sunlight
Voodoo lilies are sensitive to sunburn, so partial to full shade is recommended for these woodland plants. Your voodoo lily can grow in areas with more light, but direct rays from the sun should not be constant in the afternoon (avoid south- and west-facing locations around your home).
Temperature and Humidity
Voodoo lilies are hardy to USDA Hardiness Zones 7 through 10, although the colder regions in these zones may not accommodate this species outdoors during winter. Warm temperatures and high humidity are best. In areas that aren’t consistently humid, mist the plant’s foliage with a plant mister regularly while letting the soil dry out between waterings.
Watering
Voodoo lilies grow best with thorough waterings spaced out between periods of drying out. Too much water can collect in the depressions that form on the tuber, leading to root rot. This species will likely require more frequent watering in the summer. During the plant’s dormancy period in late summer or fall, hold off on watering entirely.
Soil
Plant your voodoo lily corm or tuber 5 to 7 inches beneath the soil’s surface. If the corm isn’t deep enough, the top-heavy plant may pull free from the soil. For a container specimen, choose a potting mix rich with organic matter. In the garden, a shovelful of leaf mold or well-rotted gardening compost will provide a welcome boost of nutrients to the corm. The soil temperature should be above 60 degrees, so gardeners should wait a few weeks after the last frost of spring has passed to plant this species in the ground.
Fertilizing
A monthly organic fertilizer rich in phosphate encourages a healthy root system (a 15-30-15 ratio is recommended). Your voodoo lily can still survive without fertilizer, but it’s best to start with a diluted fertilizer in early spring before increasing the ratio of fertilizer to water through the summer. Once your plant goes dormant, hold off on fertilizing until the growing season begins again.
Planting Instructions
Voodoo lily can be grown from seed but it will take many years for the seedling to grow into a flowering plant. Here’s how to do it:
- Collect seeds from your voodoo lily or purchase them from a reputable online source. Before planting, soak them in warm water for at least 24 hours.
- In a tray filled with moistened seed-starting mix, scatter the seeds on the surface of the soil and lightly cover with mix or vermiculite.
- Cover the tray with a plastic dome or layer of plastic wrap and place it in a sunny location. Keep the soil warm and moist (not wet) while you wait for seedlings to emerge. Germination can take several months.
- Once seedlings show themselves, remove the plastic and move the plants to a bright spot out of direct sunlight.
Pruning
The flower can be removed after it fades, but take care not to cut the emerging leaf. When the leaf fades and the plant enters dormancy, withhold fertilizer and water sparingly. The corm may rest for several months before growth resumes. At this time, continue to water and fertilize as before.
Propagation
Voodoo lilies can be pricey plants when mature, but many nurseries also sell small offsets or tubers that are more affordable. Gardeners that grow this species from tubers may have to wait three to five years to see the first bloom appear on their plant.
The best way to propagate your voodoo lily plant is via tuber offsets. This process can begin once the plant enters dormancy. Gardeners should always remember to wear gloves when handling a voodoo lily plant, as all parts of this species are toxic. Here’s how to propagate your voodoo lily’s tubers to grow new plants:
- Carefully dig up your plant’s tubers and select a tuber offset to propagate. Choose a section that has at least a few healthy roots growing already.
- Using a clean pair of gardening shears, remove the offset from the tuber system and foliage.
- Fill a heavy pot (ceramic and concrete materials are best) with soil. Ensure the pot allows for drainage.
- Plant the tuber offset 5 to 7 inches below the soil’s surface.
- Water the soil thoroughly, then allow it to dry out before watering again. Place the plant in an area with temperatures above 60 degrees and maintain high humidity.
- Once new growth appears, fertilize the plant with a 15-30-15 ratio organic fertilizer diluted equally with water. Care for the plant as usual.
Potting and Repotting
Tubers will also grow large over time, so gardeners will need to repot these plants in larger containers. Repot your voodoo lily during the plant’s dormant period in the fall. Choose a pot that has plenty of room for the plant’s roots to spread. Take care not to nick or cut the tuber, which can cause fungus and root rot or even be fatal to your plant.
The voodoo lily grows heavy on top in comparison to the size of its stem. For this reason, it’s also important to place the corm in a sturdy concrete or ceramic container that won’t tip over easily.
Overwintering
Voodoo lilies have varying frost tolerance: Know your growing zone and give your plant winter protection indoors as needed. Since this plant blooms in late winter to early spring, gardeners should prepare for its unpleasant odor during bloom time by placing the plant in a protected area like a garage that does not share air circulation with their home.
Pests and Diseases
Common Plant Diseases
The voodoo lily’s notorious odor also helps keep this species free of pests naturally. However, your plant may be susceptible to root rot when its tubers are damaged during repotting or when it’s overwatered. Take care to only water your voodoo lily once its soil has dried completely, then water it heavily (allowing for proper drainage). If the pot doesn’t offer sufficient drainage, the roots can become waterlogged.
Common Problems
While the voodoo lily is typically a low-maintenance plant for gardeners, it can still experience a few common growing problems. You may notice the following issues when growing this species:
Leaves Turning Yellow
Yellowed leaves are a classic sign of root rot, but if you’ve kept a proper watering schedule and your plant’s leaves are still changing color, it could be a sign of other problems. Sometimes, the voodoo lily yellows due to a lack of nutrients. Feed your lily with fertilizer diluted in equal parts with water.
Burnt Leaves
The voodoo lily grows best in partial or full shade. If your plant is receiving too much light, it’s common for its leaves to scorch or become sunburnt. Any crispy or dry, brown sections on the leaves can indicate that your plant needs a shadier location.
Leaves Falling Off
Changes in temperature can cause your voodoo lily to drop its leaves. This typically follows a period of the leaves changing color, however, extreme or sudden changes may lead to quick leaf drop. Always keep your voodoo lily in a location with temperatures above 60 degrees, and avoid transplanting it outdoors if the difference in temperature from your home is significant. It’s best to grow this plant outside once the weather is warm enough; allow the plant to slowly acclimate to the natural changes between seasons.
III. Uses and Benefits
- Ornamental uses
East Asia
In Japanese cuisine, konjac (konnyaku) appears in dishes such as oden. It is typically mottled gray and firmer in consistency than most gelatins. It has very little flavor; the common variety tastes vaguely like salt, usually with a slightly oceanic taste and smell (from the seaweed powder added to it, though some forms omit the seaweed).
In Japan, it is valued more for its texture than flavor. Ito konnyaku (糸蒟蒻) is a Japanese food consisting of konjac cut into noodle-like strips. It is usually sold in plastic bags with accompanying water, which is drained before cooking. It is often used in sukiyaki and oden. The name literally means ‘thread-konjac’.
Japanese konnyaku is made by mixing konjac flour with water and lime water. Hijiki is often added for the characteristic dark color and flavor. Without additives for color, konjac is white. It is then boiled and cooled to solidify. Konjac made in noodle form is called shirataki and used in foods such as sukiyaki and gyūdon.
Konjac is consumed in parts of China’s Sichuan province; the corm is called moyu (Chinese: 魔芋; lit. ‘demonic taro’), and the jelly is called “konjac tofu” (魔芋豆腐 móyù dòufu) or “snow konjac” (雪魔芋 xuě móyù).
In Vietnam, konjac is mainly grown in An Giang province. The corms are collected and processed into flour. The flour is used to make drinks, cakes, and noodles.
Fruit jelly
Konjac can also be made into a popular East Asian fruit jelly snack, known variously in the United States as lychee cups (after a typical flavor) or konjac candy, usually served in bite-sized plastic cups.
- Traditional medicine
The dried corm of the konjac plant contains around 40% glucomannan gum. This polysaccharide makes konjac jelly a viscous substance that may be used in traditional Chinese medicine.
- Vegan seafood alternative
Konjac corm powder has a noticeably fishy smell and is used as an ingredient in vegan alternative seafood products. It can be incorporated into plant-based versions of seafood. For Chinese cooking, thin strands of konjac gel can be used as a substitute for shark fins when preparing a plant-based version of shark fin soup.
- Other uses
Konjac can also be used for facial massage accessories, which are popular in Korea and gaining popularity in the West. Most commonly this is through the use of a konjac sponge, which is unique in that it can be used on sensitive skin that may become easily irritated with more common exfoliating tools (such as loofahs or washcloths).
It can be used in the formulation of drugs and devices such as oral colon-targeting drug delivery systems (OCDDS), which enable drugs to be delivered directly to the colon.
In traditional hand papermaking in Japan, konnyaku imparts strength to paper for dyeing, rubbing, folding—and other manipulations, such as momigami.
Shirataki noodles have gained popularity in the United States for their low carbohydrate content.
