Identification Japanese knotweed is a large ornamental plant that is not unattractive and this is the reason it not only made its way into this country in the first place, but is also why it is often getting away with growing so successfully in people�s gardens or on their land without interruption. We believe one of the main reasons for its success is that although most people have heard of Japanese knotweed, there is little knowledge of what it actually looks like. This means it grows quite happily for years on people�s land without the owners realising what it is they have. Only once it has established itself and become a nuisance, do they start to investigate what it is. There are some quick and easy ways to identify the plant, but it does take many forms, which is the tricky bit!
The leaf
Its distinguishing feature is its shape. It is often referred to as being shaped like a shield. It has a pointed tip that droops down at the end, it is a bright green colour and nearest the stalk, it ends with a straight/flat edge at the top nearest the stem. The flowers are cream in colour and appear in late summer, early autumn. The stems are green with red spots and look similar to bamboo in style. In winter the plant�s stems die back like other herbaceous plants and you are left with brown stalks above ground which become very brittle. During the winter the plant is still alive and is sitting dormant underground, waiting patiently for the warmer weather in spring, before being one of the first plants to emerge and start shooting.
The difference in the age of the plants
Mature plants with thick stems look similar to asparagus. A young plant that is yet to establish itself properly has a thin stem in comparison to the thicker asparagus looking shoot of a more established plant. Once established, Japanese knotweed grows in a grouping called a �crown�, where each successive year the plant builds the next layer of the crown outwards. They also send out rhizome roots from the crown to search out new areas they can spread into. Which is how they end up finding cracks and holes in building foundations or pipes to establish themselves into.
The new shoots are very red in colour and emerge quickly to beat the other surrounding plants to the available space and light. They can grow to their maximum height of 2 metres in four weeks, during spring, and so beating the competition every year. The competing plants cannot cope without the light and space they require and that�s how Japanese knotweed can take over and change a habitat. However, knotweed does provide an environment benefit at times, such as pollen from it�s flowers for insects and a bamboo structure to the undergrowth for deer to hide, so it�s not all bad! It is also safe for humans to eat, but from personal experience, has a very strong bitter taste!