Japanese Knotweed Management

Japanese Knotweed (Fallopia Japonica) is one of the most invasive plants in the UK. It was brought to the country in the 19th century as on ornamental plant before its alarming and destructive growth rate was realised. The plant may grow upto 10cm a day and up to 4 metres in height. The rapid growth of the plant means the native flora and fauna is unable to compete. Meanwhile the plants underground stem system (rhizomes) may spread over 7 metres and to a depth of 3 metres meaning very soon the plant has infested a large area and potentially caused much sub-surface damage eg. to drains and foundations. All parts of the plant, particularly the rhizomes, are able to give rise to new plants and the invasive weed can therefore be easily spread by mechanical means eg. human behaviour such as fly tipping, animals and wind etc. Japanese Knotweed is a perennial plant which dies back in the late autumn. It therefore winters giving the impression it is dead, giving no warning as to how it will thrive in the spring.

It is a criminal offence to plant or cause Japanese Knotweed to grow and the plant must be disposed of as controlled waste. WH Bond provide two methods of Japanese Knotweed control: 1. Chemical - the folian application of approved chemicals to the plant during the growing season particularly in the early autumn has a good controlling effect. Repeated treatments over two or three seasons normally removes the infestation. All operations are carried out by NPTC trained operatives using approved chemicals and overseen by a BASIS agronomist. 2. Excavation - the removal of the plant and its underground root and rhizome system is the quickest way of removing a knotweed infestation. This method takes two forms: a. Removal of all knotweed containing soils to another area where regrowth can be allowed prior to chemical control. b. Removal of all plant material and soil containing rhizomes to a suitably licensed landfill site. Both methods require great care to identify all knotweed material and isolate it. Site cleanliness is vital in order to prevent the plant being spread further within the particular site or spread off site eg. in the tracks of an excavator. Often sites require combinations of methods including the use of barrier membranes which stop rhizome growth into areas where damage would be caused.