Japanese knotweed is one of the most invasive plants in the world. It can be troublesome to identify and remove. The plant changes its appearance throughout the year. Identifying the knotweed early enough, will save you money and give you the peace of mind you need.  

However, identifying Japanese knotweed in winter can be extremely challenging as it loses so much of its distinctive characteristics such as its colour and coverage.

Identify Japanese Knotweed in Winter
Identify Japanese Knotweed in Winter so that treatment can begin

This knotweed looks like several other plants, among them bamboo. Fortunately, this article lists the distinctive features of this weed and explains how you can get rid of it.

But first,

What is Japanese knotweed?

The Japanese knotweed was brought to the UK in the late 18th century by a botanist named Phillip Von Siebold. The weed was initially growing near a volcano in the east of Asia. 

The plant was viewed as ornamental on arrival in the UK, and it was not too long before it was sold to homeowners and commercial property developers.

Where is the Japanese knotweed found in the UK?

This plant grows in all climatic conditions; it can be found in rural and urban areas in the United Kingdom. However, it is best to note that the weed grows faster in damp swampy areas.

 Characteristics of Japanese knotweed

 Here are the distinct characteristics of the Japanese knotweed:

1.     Leaves

The weed’s leaves are shovel-shaped and have a pointed tip. They are staggered on the stem hence creating a zigzag growth pattern because of their one stem per node growth design. The knotweed leaves are bright green and can grow up to 25cm long.

2.     Flowers

The flowers are in the form of long clusters with small white flowers that usually emerge in September, towards the end of summer. Each cluster measures 0.5cm wide and can grow up to 15 cm long. Together with the leaves, they form dense foliage.

3.     Stems

The stem of the Japanese knotweed resembles that of a bamboo plant. It grows up to 3 meters high. The stem has nodes and purples speckles. The leaves grow outwards from the nodes in a zigzag pattern. The stems become hollow as the plant matures; this makes it easily breakable more so during winter when the stem is extremely brittle.

4.     Roots

The underground part of the Japanese knotweed is known as the rhizome system. This stem-like structure is dark brown on the outside and orange or yellow on the inside. It can grow up to 3 meters in depth and 7 meters horizontally from the plant.

The rhizome is one of the parts of the knotweed that spreads quickly. Its tinniest fragments can flourish into a new plant.

Identify Japanese knotweed in winter dies right-back but is not dead as the rhizomes stay alive for years
Identify Japanese knotweed in winter as it dies right back. However, it is not dead as the rhizomes stay alive for years

Identifying Japanese knotweed in winter

It is hard to spot the above-ground characteristics of the Japanese knotweed more so when the infestation is over a small area. This is because the stems can be easily broken and flattened.

One of the best methods of Japanese knotweed identification during winter is keen inspection. Close examination will help identify the zigzag stems as they grow taller and become brittle. The stems will be hollow and dark brown, similar to those of bamboo.

The leaves often change their colour from green to yellow then to brown before they fall off. 

The knotweed canes die and fall on top of each other towards the end of winter. The weed starts to grow back in spring if no treatment was done during the winter season.

The downside of the up-close examination method is that one can quickly spread the weed to other areas. For this reason, it is advised that you kick off any mud or dust from your shoes before you move to an uncontaminated area. Ensure that your clothes do not have any fragments on them.

In some cases, during mild winter, you will notice large stands of the weed; the weeds’ canes standing against the wind and rains. The winter floors in a rural setup might help the plant to spread further.

As winter progresses the stems of Japanese knotweed turn brown and brittle
As winter progresses the stems of Japanese knotweed turn brown and brittle

Japanese knotweed removal

Japanese knotweed removal is made more accessible during winter because of the lack of vegetation above the ground. The brittle stems can be easily cut down and burnt or disposed of in recommending dumping sites using licensed transport.

There are several methods of eradicating Japanese knotweed. Here are some that you can take into consideration:

1.     Dig and dump

This method involves excavating the contaminated soil and dumping it at a registered landfill. The process should be done by a knotweed removal specialist to prevent improper handling, thus further spreading.

It is one of the most expensive knotweed removal methods because of the taxes that apply to the disposal. It is the method of choice when all the rest have failed.

2.     Use of herbicides

Chemical compounds containing glyphosate are effective in eradicating the Japanese knotweed. The chemical is applied to the foliage of the weed by using a bottle sprayer. It can also be injected into each stem in areas where there is a need to spare other types of plants.

The herbicides are to be used during different stages of the knotweed and seasons. This method of knotweed removal takes time to work. A lot of patience and cooperation are needed.

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

3.     On-site burial

On-site burial of knotweed contaminated soil is another of knotweed removal. This method can be considered early in the remediation process because of its sustainability and cost-effectiveness.

The first way of doing this is to bury all the knotweed waste to a depth of about 10 meters. The second way is to encapsulate the knotweed affected waste inside a buried cell constructed from a proper root barrier.

The top of the cell should sit at a minimum of 3 meters below the finished level.

Here are some advantages of on-site burial as a method of Japanese knotweed removal:

  • You do not require a license to transport the contaminated soil for disposal.
  • This method is cost-saving as compared to using off-site dumping.
  • There are fewer chances of the weed spread and encroachment.
Burying Japanese knotweed underneath an impervious membrane
Burying Japanese knotweed underneath an impervious membrane

4.     Stockpile and treat method

This removal method is suitable for extensive lands where there is enough space for stockpiling. The rhizomes with stockpiles are let to compose and are treated with herbicides continuously.  You require extensive land for proper allocations of the stockpile.

The treated stockpile should remain on-site until the knotweed dies.

Stockpile and treatment of rhizomes in a metal container prior to removal
Stockpile and treatment of rhizomes in a metal container prior to removal

5.     Root barrier

The root barrier method is used alongside other Japanese knotweed removal methods to slow down the weed’s fast spread. A specialist uses vertical root barriers at the border to prevent encroachment to the neighbouring land.

In areas where it is impossible to remove all the Japanese knotweed, they may use horizontal root barriers to protect areas such as walkways.

Japanese knotweed membrane and root barrier prevention method
Japanese knotweed membrane and root barrier prevention method

Identifying the Japanese knotweed – conclusion

Perhaps the best way to identify Japanese knotweed during winter is to consult a specialist. Additionally, it is recommended that you use an expert to remove it altogether.

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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