Japanese Knotweed (Fallopia japonica)

We're all familiar with the saying that a weed is a plant growing in the wrong place; where it is not wanted or where it causes damage or harm. With this sentiment in mind, our plant this week is undeniably considered locally, nationally and even globally as a weed. Fallopia japonica, commonly known as Japanese knotweed, is a large, herbaceous perennial of the knotweed and buckwheat family (Polygonaceae). It is native to East Asia in Japan, China and Korea but successfully established in numerous habitats in North America and Europe. It is classified as an invasive species in several countries over the world.

If there were Trump cards for weeds this would be at the top of the leader board. Japanese knotweed can be 2.1m tall and grow more than 1 meter in a month and it can rapidly re-establish from the tiniest hair of a root. These roots can grow up to 3m deep and reach up to 7m beyond where the plant is visible on the surface. Knotweed can split concrete foundations and walls creating devastating consequences to buildings and drains. According to the UK Government the annual cost of controlling the weed reached £1.25 billion in 2014. It can be controlled by injection or removal (by digging) to licensed landfill but because of the prohibitive costs, scientists have released some knotweed munching insects in areas of high humidity with the hope that they will stick to their strict diet of knotweed and begin to control the spread.

Unfortunately, it will be 10 years before it is understood whether this has been effective. In light of this weeds severity, it was made an offence under the Wildlife and Countryside Act 1981 to plant it or otherwise let it grow. In fact, if you are found to be failing to stop the spread of the plant within your property, you can be issued with an ASBO (Anti Social Behaviour Order) and fined up to £2500.

You may wonder how it came to UK. In the Early 19th Century European adventurer Philipp Franz von Siebold transported Japanese knotweed from a Japanese volcano to Holland and by 1840 he came to the UK and began to sell Japanese Knotweed to botanical gardens and the high society. It was favoured by gardeners because it looked like bamboo and grew everywhere. The very same qualities that make it so undesirable today.

Where to find it?

Throughout the Connswater Community Greenway you can see fenced off areas like the ones in the picture at Marsh-wiggle Way, the Conn O’Neill Bridge, Flora Street Play Park and Dixon Playing Fields adjacent to the river. Along the Greenway it is contained within these areas to keep it under review and treatment. If you have not noticed these areas before now you will be able to recognise them now.

Be Part of it…

If you spot any flowering plants starting to come into bloom along the Greenway send in your photos! You can private message the Greenway team on Facebook or Twitter or email them to Laura@eastsidepartnership.com