We tend to find most of our domestic customers asking if we offer Japanese Knotweed removal. We always mention that it is an offence to place Japanese Knotweed into the recycle bins as this carries an expensive fine if caught by the local authorities.
Japanese knotweed removal can be carried out in two ways, by application of herbicide or by mechanical means. The latter is always the most expensive and in some cases, the least effective. Some companies use excavators to dig out the contaminated soil. Then, they put the soil into a screening machine to separate the plant material from the soil. The small pieces of rhizome/plant are then picked up by operatives. If the soil is heavy clay and sticky it can be very difficult to separate the plant material from the soil. The Japanese Knotweed material will then either be incinerated or taken to a specialist landfill site. The Environment Agency and the Government know that the best way for Japanese knotweed removal is to keep the plant material on-site. The larger Japanese Knotweed removal companies may offer mechanical removal if treatment by herbicide is too time consuming for the client.
In case of the particular development site, Japanese Knotweed removal by mechanical means may be the only option for the developer. The main problem with mechanical removal is possible human error. It is very easy for the operative to miss tiny fragments of rhizome in the screened soil. They may be put back onto the land, thus the plant fragments could potentially lay dormant and then start to regrow. Small fragments could also be transferred between sites on the vehicles and equipment used by development company if they are not cleaned sufficiently before leaving the site.
All the Japanese knotweed contaminated soil can be dug out and taken to the specialist landfill site. The cost per cubic metre is quite expensive due to the high landfill tax. In addition, there has to be a paper trail and waste transfer licence to accompany the Japanese knotweed removal to the landfill site.
Japanese knotweed removal to other parts of the sitein the form of bunding can also be carried out. This will normally be carried out under supervision of a specialist Japanese Knotweed company. Digging out the Japanese Knotweed contaminated soil down to a depth of two metres and possibly up to seven meters out from the edge of the stand will be required. The soil will be placed on an area of the site that is not to be developed within the herbicide treatment period. The area will need to be fenced off with clear signage stating Japanese Knotweed removal contractor details.
The area will then be treated by applying herbicide. Usually, two to three years treatment followed by two years monitoring will be sufficient to resolve the problem. The contractors will update the management plan after every visit to ensure that correct procedures are followed.
Japanese Knotweed removal by herbicide treatment keeps the risk of spread off site to the wider environment to an absolute minimum. Some animals may contribute to Japanese Knotweed spread from area to area. We have been on sites where badgers and foxes have dug there sets and dens in amongst the Japanese Knotweed crowns; you tend to find that the area of contamination is great. The spread of the plant is usually due to small fragments of rhizome being attached to the animal’s fur and carried to the new areas. When foxes go out on their usual forage for food late at night they can cover miles. This is the reason when we conduct or detailed surveys we always carry out a walk of the local area to see if there is Japanese Knotweed anywhere else in the area. Many customers are quite shocked when we mention that the likely reason the plant is in their garden is due to foxes or badgers.
Japanese knotweed removal by scrupulous builders is another way that the plant can be spread the waste material tends to be fly tipped into back streets, disused waste land etc. The local authorities will then clear the waste without checking for Japanese Knotweed material. The material will end up at the local tip or at the local landfill site allowing the plant to re-establish itself.
With Japanese Knotweed removal by using spaying or injection of herbicide, you are guaranteed that the plant stays on site. It is the most cost-effective way to treat Japanese Knotweed. Professional Japanese Knotweed companies will offer the same service and guarantee to kill the plant even if treatment proceeds the two to three years.
There are situations when Japanese Knotweed removal by mechanical means cannot be used as an option due to location and disturbance to the local area. We tend to find that there are large stands of Japanese Knotweed along rivers/brooks banks. The Japanese Knotweed can be been swept down river by the strong currents. To attempt to excavate along the river/brook bank could cause the river/brook to burst its bank and cause local flooding. Railways also have a very large problem with Japanese Knotweed. The plants can be spread along the railway track by the trains.
Japanese Knotweed removal by mechanical means would not be practical or cost effective in some cases. We would suggest using application of herbicide to solve the problem. First, the modern herbicides are safe enough for humans and pets. Second, the use of herbicide minimises the risk of spread of Japanese Knotweed off site.
It is worth mentioning that in the highlands of Scotland Japanese Knotweed removal is forbidden and you could face a fine if you are caught trying to remove Japanese Knotweed. Otters use the large stands of Knotweed to secretly move from one mating ground to another undetected by humans. The otter populations in the protected areas are doing really well.