How to Control Japanese Knotweed

Time and again, trying to control Japanese knotweed has proved to be very difficult to get rid of once an infestation has occurred. This invasive type of ornamental plant is unforgiving as soon as it is allowed to spread and set camp in any zone, whether habitable or abandoned.  

Worryingly, fully grown Japanese knotweed plants often lead to the displacement of many native plant species growing within the infested area. In contrast, the deep intrusive root structure poses potential damage to property, buildings, gardens, and recreational areas. 

Based on the foregoing, Japanese knotweed control has become a paramount exercise to regulate the spread of the weed.

Notably, various approaches can be used to realize Japanese knotweed control, with each method having different results. Experts argue that it is impossible to make a case for only one method as the most effective in isolation from the other methods.

This essentially implies that all methods should be combined every so often until all infestation is stopped for one to accomplish a thorough Japanese knotweed control.

The common ways and means to attain Japanese knotweed control areas are discussed in the subsequent section:

Chemicals

Chemicals such as Glyphosate, Roundup Tree Stump etcetera are often used as a means for Japanese knotweed control where the infestation is relatively widespread.

These commercial chemicals can be readily purchased from stores authorized to sell them; hence one should not have a problem getting hold of them.

However, before one embarks on using any chemical to defeat the Japanese knotweed, it is important to familiarize yourself with its usage instructions.

Chemicals can be quite lethal to the surrounding environment and even the human body; hence taking extra caution should be paramount.

Often, for chemicals to offer the best results, experts advise that they can either be sprayed directly on the weed plants (after cutting down the canes) or, in some instances, by injecting the chemical into the stems of the weed plant.

Effectiveness: Moderate to high depending on the type of chemical used and consistency in application.

Mechanical

The mechanical methods of Japanese knotweed control involve the use of machines to get rid of invasive weeds.  Here, the main technique that is often used is mowing the plant and removing the cut fragments.

Mowing is only recommended where the Japanese knotweed is at its early stage of growth and the stems are weak.

Effectiveness: the efficiency of this method of control is low to moderate based on the fact that mowing often works on the parts of the weed plant that are above the soil surface.

What is left in the ground, i.e., the plant’s root system remains unaffected unless one takes the roots out by physical means.

However, for mowing to be effective, it is prudent that one mows an area very often and consistently so that any growth of the weed is immediately dealt with hence significantly reducing the spread.

Thermal

Although not very popular, the thermal method of Japanese knotweed control involves the use of hot water which is poured on the top of the weed plant. 

Those who use this method believe that by exposing the weed plant to very high temperatures as a result of the water, it is possible to reduce the growth rate of the invasive plant.

Effectiveness: low-efficiency method. This is because the use of hot water can only be used on Japanese knotweed plants that are young and not mature as they may be able to withstand high temperatures.

Additionally, one may incur high electrical costs as a result of constantly boiling the water for use in this method.

Physical Methods

 The physical methods of Japanese knotweed control are quite handy, but the most effective ones are:

Excavation

The Japanese knotweed is physically dug out of the soil using machines called excavators. The excavators take out the whole plant plus its roots.

This method’s effectiveness is moderate to high, depending on vigilance and complete excavation of the weed plant.

However, this method comes along with its fair share of spoils, including the heavy expenses one may have to incur to hire the machines to excavate the weed also considering excavation often involves deeper digging to get every fragment out, this poses potential damage to the area under excavation and as such one may need to dig into their pockets for the restoration of such an area lest they want to abandon it completely.

Covering/smothering

Japanese knotweed, just like any other plant, requires plenty of sunlight and moisture for it to grow continuously. Putting a protective cover that is impenetrable over the surface of the cut canes of the weed plants, deprives it of sunlight and moisture to some extent hence contributing to Japanese knotweed control.

The secret to having good results under this method is to make sure that the protective cover is completely sunlight-proof and that heavy material is placed on top of it to avoid movement or it being blown away.

Subsequently, it is advised that the periphery of the area being covered is also laid with another cover vertically to avoid any rhizomes of the Japanese knotweed escaping through the sides.

Effectiveness: Moderate. This method requires patience and constant checking on the condition of the covers used. Correspondingly, noting that taking off the cover can lead to a fresh infestation, and may force one to forever have the infested area covered, which means the land will be wasted.

Cutting and burning

Cutting the Japanese knotweed does not in itself ensure full eradication of the weed plant. This invasive plant can still spread if its cut fragments are left on the ground unattended.

Therefore, after cutting, one must let the cut pieces dry in an isolated place so that they are deprived of moisture and then subjected to burning under high temperatures to ensure that no fragment survives the process.

After this is done, one must then arrange for the burnt substances to be transported to a landfill site that is authorized to properly dispose of the delivered substance.

Want to know more about how to control Japanese Knotweed?

Knotweed Removal aims to provide the most up-to-date information, help and advice for YOU to make informed decisions. If you are unsure or uncertain about how to proceed, please reach out to us and we will gladly come back and advise you as best we can.

Governmental advice can be found here and the UK law covering the removal of Japanese Knotweed as stated under the Wildlife and Countryside Act 1981 can be found here.

The best means to contact us is via our email – hello@knotweedremoval.tips

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