It may look pretty, but Japanese knotweed has been described as “the tarmac-smashing thug invading our gardens”.
Japanese knotweed is one of the most dangerous fast-growing invasive species. The danger of Japanese knotweed does not come from its poison- in fact, the knotweed is completely edible to humans. The risk stems from its costly treatment once its identified, and the even more costly legal battles if it’s ignored.
Dangers of Japanese knotweed
Damage to buildings and roads
The plant is so powerful, it can force its way through concrete and brick causing damage to buildings and roads. It can also damage flood defences and architectural sites.
Risk to mortgages
If that hasn’t terrified you enough, the Daily Telegraph has said that infestations of Japanese knotweed can be so damaging it can block house sales and mortgage offers. An even more terrifying story involved a gardener who was so driven by worry of the plant he killed his wife…
What to do if you find yourself under the wrath of the Japanese knotweed
You may have thought, “I’ll just cut it” but unfortunately the plant is resistant to cutting and can regrow vigorously. Even disposing of the cut pieces of the knotweed needs to be handled with care.
Digging out is possible, but the plants penetrate deep underground and even if you do manage to get to the roots, you have to dispose of it at a licensed landfill site under the Environmental Protection Act 1990.
You could use chemicals such as Glyphostate on the plant during its flowering stage. More powerful weedkillers are available from garden centres or professional contractors.
It usually takes 3-4 seasons to get rid of this beast. The dangers of Japanese knotweed are quite profound.