Technical
This winter’s mild, but very wet conditions may well have promoted an early growing season for Japanese Knotweed but, in reality, this invasive, non-native plant species proves continually resilient, whatever the climatic conditions. David Layland, a founding member of INNSA and joint managing director of Japanese Knotweed Control, outlines the current scale of the UK problem and the measures being taken to counter it
Invasive Plants
Weathering the threat!
infested with Knotweed and the total annual
cost of its control in riparian habitats (excluding lakes) is some £5.6m, slightly more than the £5m it takes to control the problem on the UK’s road network.
J 122 I PC APRIL/MAY 2016 Originally native to eastern Asia and China,
before being introduced into Europe in the 19th century as an ornamental plant, Japanese Knotweed’s rapid and, at times, devastating spread is indicative of its ability to adapt to a wide range of climatic conditions. No matter how wet our summers get, or how cold our winters, the UK’s wildly unpredictable weather is never likely to seriously diminish the knotweed threat.
apanese Knotweed is estimated to annually cost the British economy some £166m. Approximately 9.2% of all rivers and canals in England and Wales, and 3.1% in Scotland, are
In recent years, our work has taken us to all
corners of the British Isles and the damage caused by widespread knotweed never fails to surprise. In the remote Hebridean Western Isles, for example, where we have carried out a number of treatment programmes, Japanese Knotweed is widespread and increasingly impacting on a number of development projects. Many plants don’t cope well with the harsh
Scottish climate, less still the bracing conditions of the Outer Hebrides but, whilst the shallow peat soils, high winds and salt air have meant that, like many plants on the islands, Knotweed’s growth has been stunted, its spread has been no less prolific, even ousting many native plant species in its wake. Japanese Knotweed, as well as other invasive
species such as Himalayan Balsam and Giant Hogweed, are all growing in increasing numbers along our river corridors, often with serious impact on the biodiversity of the riparian and aquatic environment. As rain falls and water levels rise, there is increased risk of rhizome spread along the length of the river and many river authorities are
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