Chinese knotweed (Reynoutria japonica) is an invasive plant species that originally hails from Eastern Asia. It was introduced to the United Kingdom in 1839 as an ornamental plant and has been wreaking havoc on the native ecosystem ever since.

It’s now considered one of the most invasive plant species in the world, and its rapid growth and spread pose a serious threat to native plants and animals.

So, just how tall does Chinese knotweed grow?

What is Chinese knotweed?

Chinese knotweed (Reynoutria japonica) is a fast-growing, herbaceous perennial plant that is native to East Asia. The plant has been introduced to many other parts of the world, including North America and Europe, where it is considered to be an invasive species.

Chinese knotweed flowers are small and white, and they grow in clusters. The plant’s roots are thick and deeply- rooted, making it difficult to remove from the ground once it has established itself.

What Are the Impacts of Chinese Knotweed?

In addition to being an unsightly nuisance, Chinese knotweed can also have negative impacts on the environment. The plant grows rapidly and can quickly overrun native vegetation, outcompeting other plants for space, water, and sunlight. This can lead to a decline in biodiversity as native plant species are pushed out by the invasive Chinese knotweed.

Additionally, when the plant dies back in winter, its hollow stems can collapse and create gaps in riverbanks that can increase the risk of erosion. Finally, because the plant’s roots are so thick and deeply rooted, they can damage concrete foundations, sewage pipes, driveways, patios, and roads.

Chinese knotweed flower plant grows widely
Chinese knotweed flower plant grows widely 

Mature Height

Chinese knotweed can grow up to 3 metres (10 feet) in height when left unchecked. However, its average height is 2-3 metres (6-9 feet).

The plant’s stems are hollow and its leaves are broad, heart-shaped, and roughly 4-8 inches (10-20 cm) long.

The plant’s rhizomes (underground stems) can also grow up to 7 metres (23 feet) in length, making it very difficult to eradicate once it has taken root.

Growth Rate

Another reason why Chinese knotweed is so difficult to control is its extremely fast growth rate. In ideal conditions, the plant can grow up to 20 cm (8 inches) per week!

That means it can easily outcompete native plants for resources, causing them to decline in numbers. In just a few years, an area that was once rich in biodiversity can be completely taken over by Chinese knotweed.

How Can I Get Rid of Chinese Knotweed?

Given its aggressive growth habit and negative impacts on the environment, it is important to take steps to control or eliminate Chinese knotweed if it is present on your property. Unfortunately, there is no easy solution for getting rid of this plant; removal is often a long process that requires persistence and patience.

The first step in controlling Chinese knotweed is to prevent its spread. This can be done by removing all above-ground parts of the plant (leaves, stems, flowers) before they have a chance to produce seeds. It is also important to remove any root fragments as these can re-sprout into new plants.

Once all above-ground parts of the plant have been removed, repeatedly mowing the area will help prevent re-growth from seedlings or root fragments. If you have irrigation on your property, make sure that water systems are not inadvertently spreading pieces of the plant to new areas.

Chinese knotweed can grow widely and consume a garden unless you control it
Chinese knotweed can grow widely and consume a garden unless you control it

Control Methods

Chinese knotweed is notoriously difficult to eradicate completely; however, with persistence and patience, it is possible over time to weaken the root system enough that the plant eventually dies off.

If you have Chinese knotweed growing on your property, there are a few things you can do to control its spread. Here are several methods for its removal according to which suits you best:

Method One – Digging it Up: dig up the roots and burn them; however, this needs to be done very carefully, as just one small root fragment left behind can start a new infestation.

Method Two – Cut it down: cut down the above-ground parts of the plant and spray them with herbicide; however, this will need to be done multiple times throughout the season for the best results. Repeated cutting or mowing of above-ground growth over several years until the rhizome system has been depleted enough that regrowth becomes stunted or dies off completely.

Method Three – Use of a Herbicide: applying a herbicide directly to cut stumps or actively growing plants; however, this must be done repeatedly over several years for best results as only a small percentage of herbicide actually reaches the roots where it can be effective. As with any herbicide application, care must be taken to avoid harming non-targeted plants or animals; follow all instructions on herbicide labels carefully before use.

Method Four – Hire a Professional: hire a professional company that specializes in dealing with this invasive species.

How to manage Chinese knotweed

After removal, you’ll need to keep an eye on the area for any new growth. If any appears, remove it immediately and continue monitoring until no new growth appears. If necessary, repeat these steps periodically to keep the knotweed under control.

Some herbicides can also be effective in controlling Chinese knotweed, but it’s important to be careful with these as they can also harm other plants. Glyphosate is one option that is effective against knotweed, but you should always follow the instructions on the label carefully.

Be careful not to overuse herbicides as this can force the weed into dormancy below the group d whilst you believe it has been destroyed above ground completely.

With patience and diligence, it is possible to manage Chinese knotweed and keep it under control. However, it can be a difficult task and may require repeated effort over time. If you’re not up for the challenge, there are professional services that can help you deal with the problem.

In conclusion

Removing Chinese knotweed is a necessary step in order to protect the environment from this invasive species. There are many ways to remove it, but the most effective method will vary depending on the location and severity of the infestation. By working together, we can rid our communities of this harmful plant and help preserve our natural ecosystems.

Want to know more about Chinese knotweed?

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.

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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.

Knotweed Removal, UK

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