Japanese Knotweed

Japanese Knotweed Alert!

Knotweed is a very invasive and damaging plant which has been found on several sites in East Winch recently. It’s so strong that its roots can damage foundations, paths and roads. It grows up to 2 metres high, with straight, bamboo-like stems which are green and red.

Its light green heart-shaped leaves grow close to the stem and its flowers are pink or white.

Its roots are very hard to dig up completely, and disposal is tightly regulated.

There is no law preventing people from growing it on their own property, but if they allow it to spread into neighbouring areas, they may be liable for negligence.

The best way to kill it seems to be to pour poison down the hollow stems, though this may need to be repeated the following year.

In East Winch we have a professional who can do this at reasonable cost, and I have also just been notified of another firm which can help.

So if you or your neighbours may have knotweed, please let me, as Parish Councillor, know. We do not want our village to have this problem!

Nell Steele 01553 840814

What can gardeners do about Japanese knotweed?

The eradication of Japanese knotweed is a slow process. Here are some tips from the RHS.

Non-chemical controls

Digging out is possible, but given how deep the rhizomes can penetrate, the plant usually grows back. Disposal is also a problem as Japanese knotweed is classed as “controlled waste” under the Environmental Protection Act 1990, which means you have to dump it at a licensed landfill site.

To destroy any Japanese knotweed remains on site, allow the cut canes to dry out, then burn them. On no account add them to your normal household waste.

When digging out, remove as much root as possible, then repeatedly destroy the regrowth (eg by mowing). This gradually exhausts the energy reserves in the remaining underground parts of the plant but it could take several seasons to disappear entirely.

Chemical control

You could try one of the glyphosate-based weedkillers available from garden centres. Glyphosate is usually applied to the foliage and then passes within the plant to the underground parts. It usually takes at least three to four seasons to eradicate Japanese knotweed, but professional contractors have access to more powerful weedkillers and may reduce this period by half.

Apply Scotts Roundup Tree Stump & Rootkiller to the cut canes, or try one of the other tough formulations, e.g. Scotts Roundup Ultra 3000, Scotts Tumbleweed, Bayer Tough Rootkill, Bayer Super Strength Glyphosate or Doff Knockdown Maxi Strength Weedkiller.

August 2019.