The leaves are oval in shape and late in the growing season, the plant forms clusters of creamy white flowers.

In the winter, the woody, dead stems persist and the following spring, new shoots are produced from the extensive rhizome system.

These grow up amongst the old canes to form dense thickets. Identification is possible throughout the year as its unique characteristics make it easily recognizable.

The problem
The invasive nature of this plant is due to its extremely vigorous and extensive underground root-system (rhizomes) that can extend for several metres. These roots can break through hard surfaces such as tarmac and have even been known to penetrate the foundations of houses.

Because of its rhizome root-system, any attempts at mechanical removal will often spread the infestation as root fragment as small as 1 cm can grow to form another plant. Where excavation is necessary, a minimum of 7 m clear ground around the edge of each clump should be treated as though it contains roots and care must be taken with the disposed-of material.

Warning

Any plant vegetation, soil and waste containing Japanese Knotweed could potentially cause ecological harm and must, by law, be disposed of as controlled waste in a suitably licensed disposal site accordance with official Environment Agency guidance under the Environmental Protection Act 1990

The solution
A combination of herbicide treatment and excavation will probably be required for control to
be effective.

Ideally the plant should not be disturbed earlier than 2 - 3 weeks after spraying has taken place. This will allow the herbicide time to penetrate the plant.

The Environment Agency Code of Practice recommends that soil should be excavated to a depth of at least 3 m and within a perimeter of 7 m of the plant growth area. All soil and plant matter will be required to be transported to an approved ‘controlled’ waste site for burial. All vehicles, equipment and personnel footwear and clothing must be free of seed and plant material before leaving the site.

Potential development/construction sites should be inspected for Japanese Knotweed at the earliest opportunity.

Call S H Goss for further details regarding identification, control and disposal.