Comhairle nan Eilean Siar is warning residents in the Western Isles to be on the lookout for an invasive plant that can grow up to 3 metres in a single season, rapidly dominating native plant species.

Japanese Knotweed has dense cane like stems that are red and green in colour with green, heart shaped leaves that alternate along the branch.  Its flowers form creamy clusters on the tips of most stems and flowering usually occurs between August and October.

During the Spring red shoots will appear and can grow up to 2cm a day and during the winter the plants die back leaving orange/brown hollow stems.

Residents are advised not to move the plant as it can spread very easily. Treatment with weedkiller is the only viable option in the Western Isles. Residents are advised to contact the Comhairle’s Environmental Health Section on 01851 709 578 to get advice on identification and treatment.

Contractors, developers and builders should be aware of Japanese Knotweed and the structural damage it can cause to buildings, roads and pavements.  The weed has the ability to grow up to 7m away from and 3 metres below the parent plant. 

Japanese Knotweed is classed as Controlled Waste under the Environmental Protection Act 1990 and can only be disposed of at certain licensed landfill sites. There are no landfills in the Western Isles that can accept Japanese Knotweed.

Section 14 of the Wildlife and Countryside Act 1981 makes it an offence to plant or otherwise cause the weed to grow in the wild. Care should be taken to ensure that soil from a site with knotweed is not moved elsewhere as it will spread the weed.

Japanese Knotweed should not be composted or disposed off with household waste, or in organic bins. It is an offence to do so.

Treatment using herbicides is not costly but can take a number of years to eradicate the plant.

Normal Glyphosate products are best for spraying as they are easily broken down in soil and harmless to animals.

Spraying can only take place during the growing season when there are green leaves present to absorb the herbicide and distribute it through the stems and to the root system

Most effective control can be achieved if the weed is cut or sprayed in early summer then sprayed again in late summer before the winter dieback

If the area to be treated is within 250m of a watercourse you must contact your local SEPA office, James Square, Stornoway on 01851 70 6477. 

Further guidance is also available on the SEPA website on http://www.sepa.org.uk/pdf/guidance/waste/Japanese_Knotweed1.4.pdf

Nigel Scott
Communications Officer
Comhairle nan Eilean Siar

Tel: 01851 709389 (Work)
Tel: 07884 236103 (Mobile)
email: nscott@cne-siar.gov.uk