In 1847 Japanese Knotweed was named the "most interesting new ornamental plant of the year"; by 1854 the plant was being sold commercially by nurseries.

Today the story is very different. The plant is a thug. It has no respect for boundaries, forcing its way through walls, roads and foundations, moving where it likes, and spreading with alarming speed. Figures vary, but it's believed to cost homeowners and the state over 150m a year to remove.

It blights property, and drives the owners of property in which it resides to despair and desperation.

As a homeowner, you should be aware of the basic Japanese Knotweed facts.

What does it look like?

It first appears as reddy/purple shoots, and rapidly turns into a dense growth of green, purple-speckled, bamboo like stems, growing up to around 7' or 8' tall within a few months. The leaves are heart or shovel-shaped, up to 20cms across. The stems are hollow, and there are small creamy white flowers from August to October. In the autumn, the leaves start to turn yellow, and the stems start to turn brown.

What should you do if you think you have it?

Whatever you do, don't ignore it and hope it will go away - it won't! The earlier you can catch knotweed, the less difficult it is to deal with it.

If you think it's growing in your grounds, you should seek expert advice. Good starting points are the Non-Native Specialists Association (NNSA) or the Property Care Association (PCA).It is possible to treat Japanese Knotweed yourself, but it's a difficult task. If you fail to eradicate it completely, root segments can lie dormant for years, returning to cause more problems later. Digging it out of the ground can just cause it to spread.

There are two views on the best course of action - digging up the roots, or spraying with the industrial-strength weed killer glyphosate. Or a combination of both. Either way, consult a professional, and establish the facts, and the likely costs.
What should you do if you spot it locally?

If you think you've spotted Japanese Knotweed in an adjacent garden, you should take action as it easily spreads across boundaries. If they don't take action, report it to your local Council. They, or the police, can issue a Community Protection Notice (CPN) forcing them to deal with it.

Why is it so important?

The plant is incredibly destructive to buildings and foundations. Properties are being blighted by Japanese Knotweed, making them difficult to sell. Mortgage providers frequently refuse to lend on a property if the survey mentions the plant - they will insist on the problem being eradicated by a professional before they grant a loan. And if you allow Japanese Knotweed to spread from your own land to neighbouring ground, your neighbours could take action against you.

What Streetwise can do to help

At Streetwise Environmental, we provide a treatment programme for Japanese Knotweed which involves removing as much of the root as possible, and injecting any remaining stems with a specialist herbicide, Glyphosate, to prevent further growth. All waste is removed from the site and taken to a specialist licensed tip to be burnt in accordance with the current legislation. We then monitor the effect of the treatment and follow-up with further treatments if necessary.

For advice or an individual quotation, call us on 0115 9148408 or email us at streetwise@streetwiseenvironmental.co.uk

Useful links

Occurrence records map:
https://species.nbnatlas.org/species/NHMSYS0000458716

Environment Agency advice
www.gov.uk/guidance/prevent-japanese-knotweed-from-spreading

The Streetwise Team