Scottish Parliament in talks about re-instating Hadrian’s Wall…
In recent presentations to Scottish building surveyors it became clear that many of the invasive weed problems in Scotland are a direct result of poor management of English estates.
The Victorian gardeners thought they were ‘masters of the universe’ and assumed that they could bring plants from around the world into their gardens without any consequence.
They were wrong.
Many of the problem plants of today started life as ‘flowers of distinction’ at the Royal Horticultural Gardens in Kew. Japanese Knotweed actually won an award for ‘best new plant’..!
Initially planted in the larger London houses of the 19th century many of the plants escaped the confines of the walled gardens either through seed or through mismanagement and poor handling of the cuttings. Once beyond the boundaries of these properties the alien species rapidly spread along rivers, along railways and along highways.
The pattern of spread is typical of an invasion - with a slow lag phase as the plants establish – followed by a rapid expansion phase as the plants produce huge amounts of seed. Himalayan balsam and Giant Hogweed fit into this category – both producing huge amounts of seed – but also both producing wonderful flower heads that disguise the problems that each species brings to the landowner.
Japanese Knotweed has been unusual in this regard as it does not spread by seed. The plant reproduces through what are called ‘propagules’ – which basically means that any part of the plant has the ability to re-grow. It is believed that the rapid spread of knotweed has been in part helped by the rapid expansion of the motorway network throughout the country. Contaminated machinery and contaminated soil – full of viable knotweed has been moved across the country, thus spreading the plant far and wide.
It is stated that Japanese Knotweed is present in every 10 km sq in the United Kingdom – this being largely due to cross contamination.
I have on many occasions stated that I believe that the Japanese Knotweed problem in Scotland could be contained - if carefully managed. Hence the reference to Hadrian’s Wall…maybe this is an exaggeration to suggest that a physical barrier would stop Japanese Knotweed – but perhaps it will take something this bold to stop the spread of the world’s most invasive plant?
Mike C
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