Known for its aggressive growth and resilience, Japanese knotweed can shoot to over 2.1m high, suppressing all other plant growth.
National Highways called on three sniffer dogs – Fenix the Dutch Shepherd, Spaniels Nica, and Nettle – to root out the weed and to stop it spreading.
The specially trained dogs helped by detecting the underground parts of the plant such as roots, bulbs, and shoots, which when removed prevents any spread or re-growth.
Owner and handler at Canine Detection Solutions, Kat Janczur, and the sniffer dogs started on the southern verge of the M25 site.
Each dog could only be worked for 30 mins before requiring rest for at least the same time to keep efficiency levels up.
On the second day, Kat and the dogs investigated the A3 northbound verge before heading to Seven Hills Road.
Kat said: “The dogs have got the most amazing sense of smell, and they can pick up the scent that Japanese knotweed rhizome gives off into the soil.
“They’re amazing animals and a great tool in efforts to prevent the spread of these invasive plants on and around the site.”
If not found and dealt with, the plant can cause serious problems to buildings and structures.
It’s also an offence under the Wildlife and Countryside Act 1981, to allow these invasive plant species to spread in the wild, which is why National Highways called in the dogs to help.
When dogs detect Japanese knotweed, they freeze to alert their handler.
This allowed National Highways to take action to get rid of the plant and prevent further spread.
All dogs successfully found several areas where rhizomes were located underground.
These areas would have been missed until the next season that the plant would have sprouted.
Japanese knotweed can lay dormant for up to 20 years, so using detection dogs allowed for a full site clear, regardless of the state of the plant.
Explaining the unique approach, Pippa Jordan, said: “Conservation plays an important role in our construction projects.
“Before we start, we create a map of the area which shows nearby plant species allowing us to tackle any invasive species growing on the construction site.
“In this case, we decided to put our paws on the pavement and take a unique approach to tackling the Japanese knotweed.
“These sniffer dogs are not only adorable, but also incredibly skilled at detecting the presence of unwanted plants, especially those not readily visible.”