With over 1.25 million properties effected by Japanese Knotweed in the UK and average devaluations being £23,530, knotweed is clearly a serious problem! But what does it look like? Do you have Japanese knotweed on your property? Read through our 2024 Japanese knotweed identification guide below.
To identify this invasive species in the Spring, there are many different characteristics to look out for. As it begins to emerge from the soil, it will resemble an asparagus, with tightly furled leaves. However, it will possess a dark red colour to its spike of the growth.
Once the leaves unfurl, it will leave you with a young Japanese knotweed plant that is easier to recognise. This invasive species grows at an uncontrollable rate without treatment.
For example, in spring, the plant will grow approximately 40mm per day which is over an inch and a half every day. Therefore, this means by the time it reaches May, Japanese knotweed stands can reach as tall as 1.8-2m tall.
Moving on to the Summer months, this is the prime time to identify Japanese knotweed and also the most ideal time to have the weed treated.
To begin with, the stem will look rather different from the red shoots in April. Japanese knotweed stems can reach to incredible heights of 2/3m in the summer. Also, it can grow up to 10cm per DAY, leading to dense clusters of the plant! Furthermore, another identifying feature of the stem is it’s colouring. In the summer, the stand will be hollow and green with purple speckles upon them.
Japanese knotweed leaves in the summer will be bright green in colour and in a heart-shape. Furthermore, these can reach to a diameter of 20cm across each leaf. Also, as the leafage grows, it will be in a zig-zag format across the stem, rather than directly opposite.
During the later months of Summer, great clusters of little white flowers will form on the plant. However, do not be fooled by the pretty appearance – it is still an incredibly invasive species.
Also, the Summer is when we will see the most damage. This is because the smaller stems will now be fully grown, creating pressure on any structure the Japanese knotweed is near.
As the year goes on, it’s important to learn how to identify Japanese Knotweed in Autumn before it dies off in the winter months and re-grows next spring.
In the Autumn months, the stem of the knotweed will remain green with purple speckles. However, these stems will now most likely appear in a cluster form and have similar properties to that of bamboo, as the stem will be hollow. As well as this, when identifying the species, you may notice the plant reaches great heights of up to 3 meters. Although, towards the end of Autumn, the stems may turn to a reddish-brown colour.
During the earlier weeks of Autumn, the leaves will remain green and in a heart shape. Also, through until October, your Japanese knotweed will remain to possess clusters of creamy white flowers. However, later on in the season you will notice that the leaves begin to turn yellow and start to wilt.
The rhizome is the direct cause of the spread of Japanese knotweed. In fact, these rhizomes can grow up to 2m deep and 7m wide, under the ground. Furthermore, when split open, internally, the rhizome will appear orange. On the other hand, externally, the rhizome has a ‘knotty’ and ‘woody’ resemblance. However, it is important to know that the rhizome of Japanese knotweed in Autumn can remain dormant for up to 20 years and the regeneration can start from a piece of the plant that is as small as 0.7g. Which is only about 2/3 as heavy as a jelly bean!
Knotweed displays certain characteristics in the winter to make it more recognisable to the public. As we move into winter, the leaves of Japanese Knotweed will fall from the plant and the canes will die off. Also, the canes turn brown and have a dark orange centre. However, the canes stay standing throughout the winter months and can occasionally be seen amongst new stands in the spring.
In summary, if you think you have Japanese knotweed on your property- do not touch it. It can cause serious damage to your property and the surrounding environment, and the attempted removal of it can have serious environmental and legal implications. Therefore, if you aren’t sure, and need professional advice on identifying Japanese knotweed, please contact us.
Don't spend money that you don't have to. Send us some photos of the suspected Japanese knotweed, and we will identify the plant for you.
So, let us put your mind at ease.