Frequently Asked Questions

Here are the Top Ten frequently asked questions about Japanese Knotweed. If we haven’t covered your query on the subject, please don’t hesitate to contact us at Japanese Knotweed Management.

A. Japanese Knotweed Management suggests you use the following checklist to help identify if this invasive species is indeed an issue for you.

The key things to look out for are:

  • Large leaves in the shape of a heart or spade
  • Leaves that have a ragged edge along the stem
  • The stem is hollow, a bit like bamboo
  • Fleshy shoots that may be tinged red
  • Spring – look for rapid-growing, tall stems with plenty of green leaves
  • Summer – clusters of cream coloured flowers
  • Winter – during the plant’s dormant phase the leaves will die away, leaving just the stem upright
A. Don’t just take Japanese Knotweed Management’s word for it, The Environment Agency calls it ‘indisputably the UK’s most aggressive, destructive, and invasive plant’. We don’t want to worry you, but here are some of the salient facts.

  • It takes just 10-weeks for the stem to grow three to four metres tall
  • Japanese Knotweed can grow 10cm per day, twice that when at its most prolific
  • The roots can grow three metres deep and spread up to seven metres horizontally

  • Japanese Knotweed starts growing in the spring and can reach 3m in height by June.
  • It continues to grow until autumn, dying off during the winter months
  • The length of the growing season is often dictated by the weather, with our mild winters and warm, damp summers prolonging growth.
A. In short…yes! If you have Japanese Knotweed in your garden can scare off potential buyers who would prefer not to inherit the problem or have to spend money eradicating it. Japanese Knotweed Management recommends complete removal BEFORE you try to sell.

It is also vital to note that not mentioning that you have Japanese Knotweed can result in a legal claim of misrepresentation being brought against you at a later date. In fact, it’s a legal obligation as a seller to disclose the presence of Japanese Knotweed.

A. Possibly! Probably! In effect, it’s down to the individual lender to decide, although some will reject outright any mortgage application on the basis of Japanese Knotweed being present. Some lenders will be swayed by the surveyor’s report (Japanese Knotweed Management is both a Property Care Association Qualified Technician and Surveyor in Japanese Knotweed). The majority of lenders will insist on professional removal, complete with guarantee.
A. The main problem is the speed and ease with which Japanese Knotweed grows. That said, here are some suggestions:

  • Embark on an aggressive control and treatment plan
  • If you are going to try some DIY, make sure to get as much of the plant’s root as possible and repeat the process as it may still take several seasons to have any measure of success
  • Never mow or strim the plant. It only helps it spread and grow.
  • Use herbicide weed killer
A. Unfortunately, it’s a yes. As the roots grow underground they penetrate into both walls and foundations. It’s a fallacy to say Japanese Knotweed can grow through concrete, but then it doesn’t have to. This species just finds the weakest point to exploit, growing in cracks and eventually prizing them apart. We suggest you work on this principal, if water can get through, then so can Japanese Knotweed. Knotweed can also lead to subsidence.
A. Once identified, the optimum time to chemically treat Japanese Knotweed is during the summer months. This is when the roots are working overtime to offer nutrients to the flowering plant. Just bear in mind if you’re attempting some knotweed DIY, it’s your legal responsibility to control and destroy the plant. Ignore that responsibility and you can expect fines or the possibility of a legal claim. Unfortunately, in many cases DIY only makes the problem worse.
A. Most certainly. Japanese Knotweed is a formidable foe and with regenerative qualities the envy of Dr Who, it can take up to three years to finally eradicate the species and get a clean bill of health.
A. Well, this one’s easy…call us at Japanese Knotweed Management!!!
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"Knotweed Management Company specialise in the removal and management of invasive plants, i.e. Japanese knotweed, Himalayan Balsam and Giant Hogweed in gardens allotments, buildings and rivers brownfield sites.
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