Japanese Knotweed: everything you need to know

Japanese Knotweed: everything you need to know

Japanese Knotweed can cause real problems in your garden and is notoriously hard to get rid of. Here we take a look at how we deal with a difficult problem.

Brought to Britain for its beauty, Japanese Knotweed or Fallopia Japonica is now causing a real headache for people across Britain. It grows at a very quick rate and is near-impossible to get rid of.

In its native Japanese volcanic landscape, the climate and regular deposits of ash keep knotweed plant small, but in Britain without these elements to keep it in check, it can grow up to 20cm a day. It can even grow through concrete and tarmac and its roots can grow down to 3 metres deep.

Kim Taylor, Environmental Services Area Manager tells us: “There are no natural predators of knotweed meaning the weed can grow unharmed, swamping any other plants and preventing them from getting any light.”

Identifying knotweed can be difficult as there are many other plants are suspected of being knotweed. The way you can identify knotweed is by looking out for:

  • Fleshy red tinged shoots
  • Large heart or spade shaped green leaves
  • Leaves arranged in a zig zag pattern along the stem
  • A hollow stem, like bamboo
  • Dense clumps that can be several metres deep
  • Clusters of cream flowers towards the end of July that attract bees
  • Dies back between September and November, leaving brown stems

Kim says: “Disposing of Japanese Knotweed is a long and costly procedure. All PCH Environmental Services staff have had training on identifying and dealing with knotweed but disposing of it is another matter altogether and takes years.

“Knotweed has a large underground network of roots and to get rid of the plant the roots need to be killed and the above ground portions of the plant needs to be controlled repeatedly for several years.

“Digging up the plant is one option as this is quicker but safe disposal of the plant is difficult as you need to dig down to cover the 3 metre deep roots and it is classed as controlled waste in the UK – disposing of it is regulated by law. The slightest piece of root left behind is enough for a new plant to grow again.”

Here, PCH Ranger Ryan Winsor explains how PCH approach a difficult problem: “All of our rangers have completed a Knotweed awareness course and if they come across anything it is reported and we have to verify that it definitely is Knotweed.

“The next step is a long one; we treat it over a four year plan. We visit the plant every three months and we have to inject each of the stems with weed killer, we need to do each stem as if we leave any they will grow rapidly.

“We always advise our residents not to cut it back and to report it to us so we can treat it as effectively as we can.”

If you suspect you have Japanese Knotweed in your garden then please call us on 0808 230 6500.

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