How to spot Japanese knotweed before it is too late

News at John Francis | 10/05/2022


Estate agents are all too aware of the potential problems caused by invasive plant species such as Japanese Knotweed, with a number of sales falling through over the years as a result of the much-feared visitor to our gardens. It was recently estimated that Japanese knotweed has wiped an estimated £11.8bn off the current value of the UK housing market, as the invasive plant continues to spread across the country making homes more difficult to sell. With that thorny issue in mind, Barney Packer on behalf of Japanese Knotweed Specialists, offers the following advice when it comes to Japanese knotweed, which he says is present in almost every 10sq km of the UK, and continues to spread and crop up in new places every day. When to Spot Japanese Knotweed Identifying Japanese knotweed during winter and autumn is much harder as it loses its trademark heart shaped leaves and gentle white flowers. During winter and autumn, Japanese knotweed becomes nothing more than brittle canes above the ground, but below ground, the rhizome system continues to spread. When it gets to growing season, which often begins in March or April, Japanese knotweed can grow up to 10cm a day. It will shoot out heart shaped, medium size leaves which are a lighter green in colour through its branches. In late August to October, gentle shoots of white flowers appear, which are very small and are stacked like a foxglove. How To Spot Japanese Knotweed Japanese knotweed can grow pretty much anywhere. It can grow through walls, pavements and even through the foundations of homes. You can find it in gardens, public land, building sites and even on the side of railway banks. To spot Japanese knotweed, you should look for the heart shaped leaves and white flowers in late August to October. If you have a keen eye, in March you may be able to spot the reddish shoots that appear through the ground. However, a RICS survey or a dog survey will correctly identify knotweed throughout the year and confirm any suspicions you may have. Why It’s Important to Spot Japanese Knotweed Japanese knotweed causes a multitude of problems. It can affect the progress of building works, cause issues with mortgage applications, and even leave a home with up to 25% reduced value if it grows through the foundations. Japanese knotweed will also take over a garden, outgrowing all other plants in some cases. It is important to consider the impact that Japanese knotweed can have on a building, especially if you are considering selling a home soon. While the guidance has recently been updated to help house sales go through, there is still reservation by many homebuyers to take on a home with an infestation. There’s also legislation under the Anti-social Behaviour, Crime and Policing Act that specifically refers to a landowner who allows (whether intentionally or a lack of due care) Japanese knotweed to spread onto neighbouring land. And, allowing Japanese knotweed to grow in the wild or planting Japanese knotweed will find a homeowner guilty under the Wildlife and Countryside Act of 1981, liable for a fine up to £5000.