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How to Identify Japanese Knotweed in the UK
Japanese Knotweed can be challenging to identify if you’re not familiar with its appearance. This invasive plant goes through various growth stages, changing its look throughout the year. Use our guide to help you recognise Japanese Knotweed in each season and understand its unique features.
Japanese Knotweed identification guide
How to Identify Japanese Knotweed in Spring
In spring, Japanese Knotweed begins to emerge with red/purple asparagus-like shoots. These young shoots are bright red and sprout from the crown of the plant, growing rapidly. As they develop, the leaves start to unfurl, initially dark red and then turning green. The plant’s rapid growth in spring is a notable feature.
How to Identify Japanese Knotweed in Summer
By summer, Japanese Knotweed is in full growth mode. The plant’s stems are hollow and bamboo-like, often with distinctive purple speckles. The leaves are heart or shovel-shaped, arranged in a zigzag pattern along the stems. The plant can reach up to 3 meters in height during this season, dominating its surroundings.
How to Identify Japanese Knotweed in Autumn
In autumn, the leaves of Japanese Knotweed turn yellow and begin to fall off. The plant produces small, creamy white flowers that grow in loose clusters. The stems remain standing, giving a clear indication of the plant’s location. This seasonal change helps in identifying the plant even from a distance.
How to Identify Japanese Knotweed in Winter
During winter, Japanese Knotweed dies back, leaving brown, hollow stems that persist above ground. These dead canes are a key sign of the plant’s presence even when it’s not actively growing, making it easier to spot and identify. Winter reveals the plant’s skeletal structure, aiding in its identification.
Identifying Japanese Knotweed Characteristics
How do Japanese Knotweed Red Buds Look Like
When looking for Japanese knotweed buds, look out for small red buds, which will sprout from the crown of the plant. The buds are bright and cherry-like, making them easy to spot. At this point, it can be tempting to try and remove the knotweed yourself, but should be avoided. While above ground growth is small, it is important to remember that a large network of Japanese knotweed roots already exists beneath the ground.
How do Japanese Knotweed Shoots Look Like
In early spring, Japanese knotweed shoots take the form of reddish-purple shoots sprouting from the ground. Left untreated, these will rapidly grow into the distinctive knotweed canes, but at this early point they are easily confused with the vegetable rhubarb. This is a mistake we have seen many surveyors make when examining properties, reinforcing the need for accurate professional knotweed examination. This is the ideal time to treat knotweed. The shoots are still small and the small size of your infestation means treatment options are flexible, which is why identifying Japanese knotweed early is vital.
What do Japanese Knotweed Leaves Look Like
Japanese knotweed leaves are extremely distinctive. In summer the leaves grow and are spread in a zigzag shape on the stem, with the individual leaves being bright green in colour. The leaves grow in a heart-shape, having pointed tips and straight edges. Japanese knotweed leaves look different within the different seasons, being a light green, or red colour in spring. The leaves maintain their vivid green colour until autumn where they turn brown and eventually die.
How do Japanese Knotweed Flowers Look Like
By the end of the summer, those small shoots can reach up to 3 metres in height, with root systems up to 3 metres deep and 7 metres across. By this stage, you should look out for Japanese knotweed flowers which appear as small creamy white flowers that cluster together on the vines. These flowers will remain on the plant until late autumn where they die as the stems die back.
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Why remove Japanese Knotweed?
Japanese Knotweed must be removed because it can cause severe structural damage, impacting buildings, garden structures, and underground systems. Its robust root system can exploit weaknesses in foundations, walls, and patios, leading to costly repairs. The presence of Knotweed can significantly decrease property values and complicate mortgage approvals, often requiring professional removal plans.
Legally, property owners must prevent its spread to avoid fines. Environmentally, Knotweed threatens local biodiversity by outcompeting native plants. Removal is complex and expensive, requiring professional intervention and ongoing maintenance. Addressing Knotweed promptly is essential to prevent extensive damage and financial loss.
Can I remove Japanese Knotweed myself?
Japanese Knotweed can re-grow from cuttings as small as 2mm, meaning the smallest traces can lead to new growth. Because of this, knotweed is classed as controlled waste and must be disposed of safely at a licensed landfill site according to the Environmental Protection Act (Duty of Care) Regulations 1991. This is why removal should be carried out by licensed professional Japanese knotweed removal experts.
The plant’s widespread rhizome network that could be around 2m deep and 7m in other directions, beneath the ground is still alive and will begin growing Japanese knotweed shoots again in spring.
It’s important to look out for specific characteristics for each season to know how to identify Japanese knotweed to prevent unnecessary hold ups on buying or selling your home, or any commercial building projects. We’ve put together some Japanese knotweed photos in our gallery above showing its various stages of growth.
Looking for professional help in removing Japanese Knotweed?
Our expert team offers comprehensive Japanese Knotweed removal services. We use proven methods to ensure complete eradication, backed by our 10-year Insurance Backed Guarantee. Contact us today for a consultation and let us help you protect your property.
Want to know more About Japanese Knotweed?
Plants that look similar to Japanese Knotweed
Understanding the plants often mistaken for Japanese Knotweed helps avoid unnecessary worry. Learn how to distinguish Knotweed from its look-alikes:
Giant Hogweed
Giant Hogweed is dangerous because its sap is harmful to humans through its ability to cause skin inflammations and burns when affected skin comes into contact with sunlight.
Horsetail
Horsetail is toxic, poisoning and potentially killing livestock that grazes on it, making horsetail removal a particular priority in the eyes of the farming and agriculture industries if found on land.
Himalayan Balsam
Himalayan Balsam can reach heights of over two metres, and is aggressively invasive. Due to legislation around spraying chemicals in the wild and near bodies of water, it is safest and most effective to hire professionals that can adhere to laws and best practice.
Law and Legislation on Japanese Knotweed in the UK
Japanese Knotweed is subject to strict regulations in the UK. Learn about the legal responsibilities of property owners and the steps you need to take to comply with the law.
Everything about Japanese Knotweed
Explore our comprehensive guide that covers everything from the plant’s history and biology to its spread and control methods. This resource is perfect for those looking to understand Japanese Knotweed in-depth.
Get in touch
Need more information or assistance? Contact us through our website or call our hotline. We’re here to help with all your Japanese Knotweed concerns.
