Japanese knotweed is an invasive plant that has bamboo-like stems and heart-shaped leaves.
While the plant may look somewhat attractive, it’s actually incredibly invasive and can even cause damage to hard surfaces, block drains and make cracks worse.
The plant grows rapidly at this time of year and produces white flowers in late summer and early autumn.
The plant’s canes can grow to be 2.1m tall and are known to have purple flecks.
Japanese knotweed cannot set seed or propagate via seed in the UK but the plant can sprout from even the smallest amount of rhizome left in the ground.
However, experts are warning that there are Japanese knotweed “hybrids” growing in the UK. A hybrid plant is the offspring of two different plant varieties which have cross-pollinated.
Jennifer Holmes at Japanese knotweed.co.uk said hybrids have “different traits to their origin plant species but can look very similar”.
She said in a post on the website: “Since one plant may be toxic and the other not, it is important we know how to tell the difference.”
How to identify Japanese knotweed hybrids:
Giant knotweed
Giant knotweed has enormous leaves, heart-shaped leaf-bases, curled hairs on the underside of the leaf and long, fluffy clusters of flowers.
These plants are very similar to hybrid knotweed but a lot larger. They can grow to be four metres in height, have leaves that can grow to be between 20cm and 40cm and have flowers that have a green hue.
Himalayan knotweed
These plants are shorter at just one metre in height and have long, slender leaves. The undersides of the leaves are paler than the top and they are evenly spaced down the stem.
The flowers are creamy white and pinkish and are slightly fragrant as well as being different lengths.
Dwarf knotweed
These plants are even shorter, have curl-edged leaves and can form other hybrid varieties.
This plant can reproduce from seed which means the main problem is it can form other species like giant knotweed.
Hybrid knotweed
This hybrid has crinkly leaves, short hairs on the underside of the leaf and heart-shaped leaf bases.
The leaves are a slightly darker shade of green and the mature leaves are bigger.
The plant is formed by giant knotweed and Japanese knotweed and is one of the most successful of the knotweed hybrids, according to The Knotweed Company Ltd.
The plant can be vigorous and persistent and is being spotted more in the UK and Europe.
