Description
Amorphophallus konjac (Amorphophallus konjac, family Araceae)
Amorphophallus konjac is a rare and unusual herbaceous perennial tuber native to the warm tropical regions of Eastern Asia. It is mostly grown for its ornamental appeal, producing bold, palm-like foliage on a mottled stem that can reach around 1 metre tall. Once the tuber has matured, usually after about three years or when it reaches the size of a grapefruit, it has the potential to produce a spectacular plum-coloured flower in late spring to early summer. Blooming is rare and occurs only once every few years, making its appearance all the more special. Even without flowering, the dramatic foliage alone makes this plant a standout. Despite its exotic origins, Amorphophallus konjac adapts well to cooler climates, making it a plant that gardeners everywhere can enjoy.
Benefits and Uses
Beyond its striking ornamental presence, Amorphophallus konjac also has a rich culinary history. The tubers are edible once they have been cooked or dried and are valued as a natural thickener in food. In Japan, they are traditionally processed into konnyaku, a firm yam cake, and shirataki noodles, both of which are prized for their unique texture and health benefits.
Where to Plant
Amorphophallus can be planted directly into sheltered garden beds or grown in large containers. In beds, allow space for the plant to reach its mature size of around 1 metre tall and wide. For pots, select a large and deep container with good drainage to accommodate the tuber’s growth and to make repositioning easier during its growing and dormant phases. In cooler climates, container growing is often the best choice, as pots can be moved to warmer, sheltered positions when extra protection is needed. Whether grown in beds or containers, always choose a site protected from wind to prevent damage to the tall leaf stalk.
Climate Suitability
Amorphophallus konjac is suited to cool to tropical climates. In warmer regions, it grows best in part sun to light shade, while in cooler climates, it benefits from a full sun to part shade position, where the extra warmth encourages strong growth while still protecting the foliage from burning. During winter dormancy, protect from frost to ensure the tuber remains healthy.
When to Plant
Plant in spring once the soil has begun to warm. In warmer climates, planting can be done earlier in the season, while in cooler regions it is best to wait until the risk of frost has passed and conditions are consistently mild. Tubers remain dormant through winter and will naturally begin to sprout as the weather warms, showing small pink shoots that indicate they are ready to be planted.
Location
Plant Amorphophallus konjac in a warm, sheltered location with protection from wind and afternoon sun. In warmer climates, it thrives in part sun to light shade, while in cooler climates, it benefits from a full sun to part shade position. As the flower emits a strong odour when it appears, avoid placing plants near windows, doorways, or high-traffic areas.
Soil
Enjoys a moist but well-drained soil that is rich in organic matter. Adding compost before planting helps improve fertility and drainage, giving the tuber the best start. Avoid heavy clay or waterlogged soil, as this can cause rot.
How to Plant
Plant tubers at a depth approximately twice their height, usually 10–20 cm below the soil surface, depending on size. Larger tubers should be set deeper to accommodate their growth. Position with the neck facing upwards, as this is where the roots emerge. Space 45–70 cm apart to allow for their mature spread of around 1 metre. Water lightly after planting, keeping the soil just moist until new growth appears.
Watering
Keep the soil evenly moist once new growth emerges in spring and throughout the active growing season. Water regularly to support the large leaf and developing tuber, but avoid waterlogging as this can cause rot. Reduce watering as the foliage begins to die back and cease completely during winter dormancy, as the tuber requires dry conditions while resting.
Fertilising
Fertilise during the growing season to encourage strong leaf and tuber growth. Apply a complete fertiliser at the start of active growth or use a tomato fertiliser as an alternative, as it has shown good results. Avoid over-fertilising, as this can cause soft growth and reduce flowering.
Mulching
Apply a layer of organic mulch, such as sugarcane or bark, around the base after planting to help retain moisture, regulate soil temperature, and suppress weeds. Mulching also provides added protection in hot and cool conditions. Keep mulch clear of the tuber to prevent rot.
Division and Storage
Tubers can remain undisturbed for many years, but dividing mature plants every few seasons helps maintain vigour and healthy growth. Divide during winter dormancy once the foliage has completely died back. Replant divisions immediately into soil or pots, or store them in a cool, dry, well-ventilated place until spring. In cool climates, lift and store tubers or move large pots to a warm, sheltered, frost-free position until spring. Replant once the soil has warmed and small pink shoots begin to appear.
Safety
The tuber is edible only once cooked or dried and should never be eaten raw, as it contains compounds that can irritate if ingested. Keep plants and tubers out of reach of children and pets. While not known to be a skin irritant, those with sensitive skin may wish to wear gloves when handling.
Supplied as a dormant tuber.