The latest hotspots for the destructive Japanese Knotweed plant in the Largs and Millport area have been revealed.

Native to East Asia, Japanese knotweed was introduced to the UK in the 1800s and has since become one of gardeners' most dreaded invasive species.

It can grow up to four inches a day and forms dense thickets which can kill native plants and damage infrastructure.

Japanese knotweed is identified by its red stems and a bamboo-like appearance. It can grow up to eight feet tall, though its roots can be as long as 28 feet.

According to research by invasive plant specialists Environet, the most common place for Japanese Knotweed in the area is not Largs itself but Cumbrae, where there are seven occurrences within a 4km radius of Millport - and a further six in a 4km zone at the north end of the island.

Six cases were recorded within 4km of West Kilbride, and there were three within 4km of the A78 between Largs and Skelmorlie, as well as two at or near the A760 between Largs and Kilbirnie.

However, the Environet research indicates that there are currently no recorded cases of Japanese knotweed in Largs itself, nor in Fairlie.

Largs and Millport Weekly News:


If Japanese knotweed is found on private property, the law states that the land owner must take the necessary steps to prevent any further growth.

Those who come across Japanese knotweed should not cut, mow, or trim the plant as it will grow back from the root - and there's also a high risk of fragments of the root or stem growing into a new plant.

The only way to be sure of killing the plant is by applying herbicides over the course of several years.

A spokesperson for the Scottish Invasive Species Initiative said: “Due to its persistent rhizomes and ability to regenerate, research suggests the only effective way of controlling knotweed is by herbicide (glyphosate) application.

“Treatment is needed over subsequent years. While initial success can be achieved in the first year, at least some of the root will remain and will grow to form a new stem if the treatment isn't followed up in years two to three.

“The average time for a chemical treatment programme is three to five years.”

For more information on how to deal with Japanese Knotweed and to report a sighting to the Scottish Invasive Species Initiative, see

To see Environet's full map, visit