People could unwittingly be spreading Japanese Knotweed, one of the most destructive plants, rather than eradicating it thanks to poor guidance from councils, say researchers from the University of Exeter. While some of the local councils were found to be giving good advice, some weren’t or were giving inconsistent messages.

The bad advice being given by the local councils could either cause needless worry or spread the plant further around the country. For any reader looking to get a knotweed survey done then see here.

What Is Japanese Knotweed?

Japanese Knotweed is a perennial plant that’s native to Japan and related to buckwheat. Its stems are capable of reaching around chest height and it grows in dense clumps. Many non-Asian countries have declared it an “invasive species”.

In 1850, Philipp von Siebold, a botanist, sent samples collected on the slopes of a Japanese volcano to the Royal Botanic Gardens in Kew, according to the Daily Mirror. Within 4 years, the plants were being touted as useful new fodder for animals and sold by commercial nurseries.

Why Are People So Unhappy with It?

For 3 primary reasons. First, it has a remarkable ability to force its way through brick or concrete, which means that it can damage roads or buildings. Second, it grows in dense clusters which usually exclude the native species. Third, eradicating it is nearly impossible.

Is It Really So Bad?

Japanese knotweed is without a doubt one of the UK’s most destructive, aggressive, and invasive plants according to the Environment Agency. Besides destroying concrete foundations, it can manage architectural sites and flood defences.

The plant is so hard to control and destructive that lenders may refuse mortgages on homes facing a ‘knotweed problem’ and house sales can even fall through. The Telegraph reports that one gardener killed his wife after being “driven mad by worry” about the plant.

The Guardian reports that knotweed can grow 3 to 4 meters in just 10 weeks. Its roots can spread 7 meters horizontally underground and the plant is capable of re-growing from just a tiny fragment of its root, which means that eliminating it is far from easy.

How Can You Eradicate It?

Japanese knotweed is resistant to cutting because it’s known to regrow vigorously. Any cut pieces must be disposed of carefully. Casual gardeners are advised to call in professionals for disposal. Chemical herbicides, however, can destroy the plant. Experiments suggest spraying some seawater on the leaves. This can also be an effective solution if the herbicide isn’t available.

How Does the Plant Reproduce?

In Asia, the plant has both a male and female variety. However, only the female has reached the UK, which means that the plant is incapable of reproducing sexually via pollen. Undaunted, the female plant that found its way to the UK has cloned itself over and over again.

Each separate plant of Japanese knotweed in the UK has regrown from another plant’s root. Often, these have been unwittingly moved by councils or gardeners taking earth from one site to another.

Why Is Japanese Knotweed Sometimes Referred to as ‘Britain’s Largest Female’?

Since they aren’t reproduced sexually, all the clumps of Japanese knotweed found in the UK are technically the same plant, even if they are not joined together physically. So, it is the largest female in Britain or perhaps even the world.