Japanese Knotweed control methods

Once Japanese knotweed has become established, Japanese Knotweed treatment and removal can be very challenging. The Royal Horticultural Society states on its website: ‘eradication requires steely determination’. Knotweed Services UK offer a range of successful Japanese knotweed treatment methods. Take a look below for Japanese knotweed treatment methods that we use.

Japanese knotweed has spread across the country at a fast speed. When you consider that it doesn’t form viable seed in Britain but spreads through bits of the rhizome that have become detached from the main root-mass. In fact, all the plants recorded in Britain so far have been female. Any seeds formed are hybrids with another species.

Japanese Knotweed is very common on sites that are disturbed by human activity. Such as:

  • Railway lines.
  • Old allotments.
  • Rubbish tips.
  • Derelict land.

The main cause of the spread of Japanese knotweed has been because of:

  • The transferring of soil.
  • Rubble and rubbish between sites.
  • It can also spread from site to site through bits of root stuck to machinery and tyres.
  • It can spread rapidly down watercourses.
  • Floods will easily dislodge rhizomes, which are carried downstream to start new colonies.

Effective Japanese Knotweed control methods.

Herbicides/stem injection

Pros

  • Cost effective
  • Treatment can be be carried out in situ without the risk of spreading plant further

Cons

  • Takes 3 to 5 years or more
  • Must be left undisturbed
  • Restrictions remain on site
  • Restricted use near valuable vegetation and waterways

Crown removal

Pros

  • Removes the vast majority of underground biomass
  • Increases the effectiveness of herbicide treatment
  • Reduces the time required for herbicide treatment

Cons

  • Can be expensive or time consuming, particularly for large infestations
  • An area to store the removed crown may be required
  • The area must be left undisturbed
  • Restrictions remain on site

Stockpiling

Pros

  • Cost effective
  • Allows development works to be undertaken whilst treatment takes place elsewhere on-site

Cons

  • Requires undisturbed area
  • Soil from stockpile must remain on site
  • Restrictions remain in stockpile area

Screening

Pros

  • Moderately cost effective
  • Allows development works to be undertaken whilst treatment takes place elsewhere on site

Cons

  • Requires incineration to take place – potential issues gaining consent to burn
  • Only reduces level of infestation, does not rapidly eliminate the plant
  • Requires set-aside area on site for spreading out of smaller rhizome fragments

Burial

Pros

  • Does not require a set-aside area for control
  • Work can continue immediately after burial

Cons

  • Restrictions remain on site
  • Limits use of area above burial site
  • Requires a large hole to receive material

Removal to landfill

Pros

  • No restrictions left on site
  • Work can continue immediately after removal

Cons

  • Relatively expensive

Japanese Knotweed control methods in detail.

Herbicides and stem injection

We use powerful chemicals. We apply chemicals away from other plants because chemicals can burn other plants it comes into contact with. The most effective time to apply herbicides to Japanese knotweed is in Spring.

This is much more damaging to the underground rhizome system than applying herbicides in Spring. A qualified person should carry out any treatment that involves the use of chemicals due to their powerful and harmful nature.

Stem injection – we apply a controlled amount of herbicide directly into the Japanese knotweed plant. Due to being injected directly into the plant, this is the most crafty method of removal. Unlike other spraying methods (more traditional) it is not dependant or compromised by weather conditions.

With traditional spraying methods, the environment has to be taken into account because rain or wind could cause the chemicals to spread to other species and have the potential to be harmful. Due to the nature of the stem injection procedure, it is 100% safe.

Japanese knotweed Crown removal

Crown and stems are capable of regenerating and even small fragments of cut crown or stem are capable of regenerating and becoming a new plant.

New plants will grow from the nodes of pieces of green stem, in soil or water. Mechanical cutters, will spread knotweed in this fashion. If stems are dried until they are dark brown, they will not regrow unless the crown (base of the stem) is still attached.

Crown removal is exactly what you would expect from the title. By removing the cranes of the Japanese knotweed plant, we remove the majority of biomass that is underground. With the crowns removed – our herbicide and stem injection treatments are much more effective.

Even the smallest piece of rhizome, stem or crown can potentially form a new plant – removing these from the equation is a great strategy.



Stockpiling

Stockpiling and bunding is the method of relocating contaminated Japanese Knotweed soil to a different area of the site being treated. A bund is a shallow area of the contaminated soil, typically 0.5m deep.

The bund can either be raised, on top of the ground, or placed within an excavation to make the surface flush with the surrounding area.

The purpose of the bund is to move the Japanese knotweed to an area of the site that is not used. This ‘buys time’ for treatment that would not be possible where the Japanese knotweed was originally located.


Screening

Soil screening/sifting is much like excavation and removal but instead of extracting all of the soil impacted by Japanese Knotweed, we only remove the infested parts of the soil. It is an effective, productive and maintainable Japanese knotweed control method that allows the reuse of the previously infested soil. Reducing the use of landfill.

This method is most effective when used in conjunction with other control methods. For a large scale site, heavy duty plant machinery is typically employed. For a domestic property, a small digger will scrape back small layers of soil at a time and one of our surveyors will remove any rhizome as they’re unearthed.


Burial

After uprooting, cutting or clearing of the Japanese Knotweed, the remaining soil or the area where the weed may have been treated with chemicals before being buried where excavation occurred. We bury the Japanese knotweed at least 5 meters deep under topsoil.

The burial requirements for Japanese knotweed are as follows:

  • With 5 m of soil on top. A root barrier must be placed on top of the knotweed material
  • Completely encapsulated in a root barrier membrane cell at 2m
Remove to landfill

This method is the excavation of any and all soils containing the possibility of Japanese knotweed rhizome.

These are then loaded into a large vehicle and transported to a licensed landfill site and then disposed of safely. Dig and Dump will rid you of Japanese Knotweed when other solutions will not.

Any waste taken off site must be taken by a licensed waste carrier and go to a suitably authorised landfill site.


Some of the people we have helped…