Common name:Japanese knotweed
Scientific name:Fallopia japonica
Alternative common names:
Monkeyweed, monkey fungus, Hancock's curse, elephant ears, Japanese bamboo, American bamboo and Mexican bamboo.
Japanese knotweed is an herbaceous perennial with tubular, glabrous stems that ascend from an erect base. It has hollow stems with distinct raised nodes that give it the appearance of bamboo. While stems may reach a maximum height of 3–4m each growing season, it is typical to see much smaller plants in places where they sprout through cracks in the pavement.
Where does this species come from?Eastern Asia in Japan, China and Korea.
What is its invasive status in South Africa?Listed as a Prohibited Species (No.73) under Notice 4 - List of Prohibited Alien Species in terms of Section 67 (1) in the NEMBA Draft Regulations of 12 February 2014.
Where in South Africa is it a problem?KwaZulu-Natal.
How does it spread?It spreads via its crown, rhizome (underground stem) and stem segments, rather than its seeds.
Why is it a problem?The invasive root system and strong growth can damage concrete foundations, buildings, flood defences, roads, paving, retaining walls and architectural sites. It can also reduce the capacity of channels in flood defences to carry water.
What does it look like?Leaves: The leaves are broad and oval with a truncated base, 7–14cm long and 5–12cm broad, with an entire margin. Flowers: The flowers are small, cream or white, produced in erect racemes 6-15cm long. It flowers from July/ August to September/October. Fruit/seeds: The fruits are shiny, dark brown, triangular nuts, 2-4mm long.
Interested in the Japanese knotweed invasion in the United Kingdom.