What Does Japanese Knotweed Look Like?

What Does Japanese Knotweed Look Like?

What does Japanese knotweed look like?

Would you be able to identify Japanese Knotweed in the grounds of a property? What if you are purchasing a house during the spring, how different would Japanese Knotweed look compared with how it looks in the summer?

Being able to identify Japanese Knotweed is perhaps a skill that could save you money (and a lot of heartache) when purchasing a house. But what does Japanese Knotweed look like throughout the seasons? Like most plants, Japanese Knotweed changes in appearance throughout the year. It will die off in the winter leaving brown dead stems but come the spring it will rapidly produce new shoots and leaves for the summer and autumn. Japanese Knotweed usually grows from around April to October and the plant is most easily identifiable during mid-summer, with bright green leaves and small white flowers. By looking at pictures of Japanese Knotweed throughout the seasons one can develop the ability to identify Japanese Knotweed, a useful skill when looking to purchase a property.

Japanese knotweed in spring

The fastest Japanese knotweed growth is during the spring. New shoots that emerge are red/purple and can look like asparagus spears. The leaves are normally rolled up and dark green or red in colour. In late spring, canes can reach up to 3 metres (10 feet) high. The pictures below show Japanese knotweed in spring.

Japanese Knotweed in Spring - typical asparagus-like red tips are shooting through the soil
Tell-tale red shoots appearing
Japanese Knotweed in Spring - the rolled up leaves are starting to spread out
The rolled up leaves are starting to spread out
Japanese Knotweed in Spring - canes are shooting up and leaves are turning green
Canes are shooting up and leaves are turning green

Japanese knotweed in summer

During the summer the knotweed leaves are green and heart/shovel shaped and can be 20cm across. In late summer early autumn small clusters of white flowers will appear. The stems are mostly hollow and bamboo like and the general growth habit has a distinctive zigzag appearance. The photos below show what Japanese knotweed typically looks like in summer.

Japanese Knotweed in Summer - Leaves are shaped like a shovel/heart
Leaves are shaped like a shovel/heart
Japanese Knotweed in Summer - Small clusters of white/cream flowers appear
Small clusters of white/cream flowers appear
Japanese Knotweed in Summer - Stems grow in a zig-zag fashion
Stems grow in a zig-zag fashion

Japanese knotweed in autumn

In Autumn the dense covering of leaves will remain, however, they start to turn yellow and wilt as we move into September and October. The knotweed plants are still about 2-3 metres tall and the hollow stems start to turn brown. See our images below to identify Japanese knotweed in Autumn.

Japanese Knotweed in Autumn - Leaves start to yellow
Leaves start to yellow
Japanese Knotweed in Autumn - Autumnal colours appear across the plant
Autumnal colours appear across the plant
Japanese Knotweed in Autumn - Moving into September and October, the yellowing leaves start to wilt
Moving into September and October, the yellowing leaves start to wilt

Japanese knotweed in winter

During late autumn and the beginning of winter the knotweed canes die off and the weed becomes dormant. The leaves turn yellow, then brown and fall off. The canes are hollow, dark brown and brittle and they collapse upon one another. If the area hasn't been treated, often previous year's decomposition can be seen underneath. See the images below to identify Japanese knotweed in winter.

Japanese Knotweed in Winter - Canes turn brown
Knotweed canes turn brown
Japanese Knotweed in Winter - leaves turn brown and drop off
The leaves have turned brown and dropped off
Japanese Knotweed in Winter - The canes are hollow and resemble bamboo
Japanese knotweed canes are hollow and resemble bamboo canes

As these pictures demonstrate, Japanese Knotweed can change considerably in appearance throughout the seasons. When looking to buy a property it is very important to be able to identify Japanese Knotweed and if you suspect that knotweed is present, you may wish to put a Knotweed Management Plan in place to deal with the problem and to satisfy most mortgage lenders.

More Information

For further information on identifying Japanese knotweed, see our Japanese Knotweed Identification webpage here.

For help with identification please email your photos to contact@knotweed.co.uk or call 0333 2414 413

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