IT would be too costly and time-consuming to completely remove fast-growing Japanese Knotweed from canals, river beds and the hedgeways of Birmingham, a year-long city council investigation has concluded.

The best that can be achieved is to “control and manage” the plant, which can smash its way through concrete and grows at the rate of 2cm a day.

Since its arrival in the UK in the late 1800s as an ornamental plant, Japanese Knotweed has spread rapidly across the country and is stifling and killing native flora and fauna.

It has proved to be immune to pests and diseases and is making its way from the countryside to towns and cities.

An appeal by the council for the public to report knotweed outbreaks saw sightings rise month on month.

Four were reported in March, nine in April, 12 in May and 23 in June.

The weed has been identified in about 100 locations, but the true extent of the outbreak is thought to be far greater.

Problem sites include Cannon Hill Park, Boldmere Golf Course, Hodge Hill Common, the River Rea, Selly Park and Pershore Road Nature Centre.

Trials conducted by the council into ways of controlling Japanese Knotweed found the best option to be the use of herbicide Glyphosate three times a year until the infestation is “brought back to a manageable condition”.

Cabinet leisure, sport and culture member Ray Hassall admitted the vast majority of outbreaks have not yet been identified and are not on a programme for treatment.

Information on how to identify and treat the weed has been posted on the council website.

Coun Hassall (Lib Dem Perry Barr) added: “The management and control of Japanese Knotweed will remain a key issue for many years to come.

“There is an important role for the city council to play in maintaining a watching brief on all of the latest research and best-practice in relation to the control of Japanese Knotweed.”

He said the “fundamental point” to have emerged from research was that it would be un-economic to try to remove the weed completely.

“It is something that needs to be controlled and managed,” he added.

Initial claims that the council would face a huge bill to control Japanese Knotweed proved to be baseless, according to Coun Hassall.

He said costs could be contained within the grounds maintenance budget.