Japanese knotweed in autumn

For several years,  most people did not see the Japanese knotweed as a significant threat to the ecosystem.  The weed arrived in the UK as an ornamental plant; its beautiful leaves and flowers deceived several properties and homeowners into planting it.

The knotweed looks different during each of the four seasons.  Thus, it is necessary to be able to identify Japanese knotweed in autumn and other seasons so that you can plan for fast removal, that is if you have the weed on your property.

The Japanese knotweed’s potential to cause massive damage to infrastructure has been ignored over the years. This knotweed species grows rapidly and deeply into the soil, causing cracks on house floors, and walls, and damages to the drainage systems. 

In this post, we have described the features of the Japanese knotweed in autumn to eliminate the chances of mistaking it for other plants.

Features of Japanese knotweed in autumn.

The Japanese knotweed’s leaves broaden and grow up to 20cm during summer. They grow in a zigzag pattern from the stem. Small clusters of flowers start appearing as autumn approaches. 

At the beginning of autumn, the Japanese knotweed has dense foliage. The leaves will begin to turn yellowish some weeks into the season, they then start wilting towards the end of September.  During this period, the plant is about 3 meters tall in summer.

The hollow stems now resemble those of bamboo; they change their colour from brown greenish to deep brown. The stems will then become brittle and die, and the canes could still be standing after months of browning.

Japanese knotweed in Autumn with leaves turning yellow and stems beginning to turn brown
Japanese knotweed in Autumn with leaves turning yellow and stems beginning to turn brown

Knotweed growing from adjoining property

Where the knotweed is growing from adjoining land, you should coordinate with your neighbour to get rid of it as early as possible. It is also best to involve as many community members as possible; this awareness ensures that the weed does not spread from property to property.

What do I do if I have Japanese knotweed in my garden?

Here are some guidelines you have to adhere to when you have Japanese knotweed in your garden.

 Do’s

 Don’t

  • Do not buy any more time when you find Japanese knotweed on your property.
  • Do not contaminate any natural resources with the weed; this will damage the existing ecosystem.
  • Do not buy topsoil from any seller unless it is correctly inspected for Japanese knotweed.
As summer ends, Japanese knotweed in autumn starts dying back and the leaves turn yellow
As summer ends, Japanese knotweed in autumn starts dying back and the leaves turn yellow

Killing Japanese knotweed

There are several methods used to eradicate Japanese knotweed in autumn.  Here are the most effective ones:

1.     Dig out method

The most common one in small areas is to dig out the method. This involves digging out the rhizomes system. One way that the weed spreads is through its root system. This means that you can quickly eliminate the plant if you dig out the roots completely.

The knotweed root pieces must be removed carefully to ensure that no fragments are remaining in the soil. Disposing of waste is another major factor you have to consider if you decide to use this method.

There are solid laws in the UK on how to dispose of Japanese knotweed properly. The waste should strictly be arranged in a licensed landfill facility. 

2.     Use of glyphosate herbicides

The knotweed can be killed using different herbicides. However, much success has been achieved using chemicals that contain Glyphosate.  Glyphosate is a translocated herbicide; this means that the plant carries the herbicide down the rhizome.

Some of the popular contact herbicides are only able to kill the stems and the leaves but not the roots. This explains why they are less effective when it comes to Japanese knotweed removal.

Herbicides are useful when used during spring. The Japanese knotweed was extremely leafy during this season. The chemical should be sprayed with a lot of caution so as not to spread to the nearby plants.

You may not notice much change until 30 days are over. You need at least three rounds of spray for about three years to eliminate the plant.

In most cases, by the third year, the Japanese knotweed growth will be less than 1 meter in height; treatment should be continued until no plant emerges.

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3.     Meshtech method

Meshtech is an eco-friendly Japanese knotweed removal method hence ensuring the preservation of the life of plants and animals in the ecosystem. With this method, you rest assured that you will not pollute the air or cause soil structure disturbance. Being a new method, it is not used by all contractors but it is worth contacting a contractor to find out if they favour this method to solve your knotweed problem.

The mesh tech method ensures that the stems are cages to prevent them from growing taller.

Spraying Japanese knotweed in autumn and other unwanted weeds with glyphosate herbicide
Spraying Japanese knotweed in autumn and other unwanted weeds with glyphosate herbicide

 Not able to identify Japanese knotweed?

Japanese knotweed identification can be quite tricky because of the several plants that are mistaken for the weed all year round. To avoid inconveniences and unnecessary panic that comes with mistaken identity, we advise hiring a weed specialist to determine the plant.

Do not ignore the fact that many plants look similar to Japanese knotweed. An expert will be in a good position to advise you accordingly.


Want to know more?

Knotweed Removal aims to provide the most up-to-date information, help and advice for YOU to make informed decisions. If you are unsure or uncertain about how to proceed, please reach out to us and we will gladly come back and advise you as best we can.

Governmental advice can be found here and the UK law covering the removal of Japanese Knotweed as stated under the Wildlife and Countryside Act 1981 can be found here.

The best means to contact us is via our email – hello@knotweedremoval.tips

Do not forget we have a library of blogs covering many areas relevant to Japanese Knotweed, our free downloadable How-to Guides and Product Reviews on the latest methods being employed to eradicate or remove Japanese Knotweed.

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