The Japanese knotweed goes by the scientific name of Fallopia japonica. You may know it by other names as it has a myriad of these. From Fleeceflower to Mexican Bamboo through to Japanese Polygonum, it has quite many English names.
It also has variation in its scientific names, such that it also goes by the names Reynoutria japonica and Polygonum cuspidatum. However, throughout this article, we will refer to this plant as Japanese Knotweed or Fallopia japonica.
This article will delve into this plant and its effects on the environment and the economy. Furthermore, it will cover the various ways in which you can manage knotweed infestations in your home.
This weed is native to the eastern part of Asia, with a presence in Taiwan, China, Korea, and Japan. Its introduction to the United States took place towards the end of the nineteenth century. At the time, people regarded it as an ornamental plant and planted it as such. It also served as a means to manage soil erosion, as well as a source of food for animals.
Following its cultivation, it was not long before escapes of the plant made their way across vast distances. In so doing, it became an invasive plant, calling for a need for control measures. At present, it is invasive in North America, New Zealand, Australia, and Europe.
Not only does it pose a threat to society, but it also hurts the environment and the economy. It does so by the creation of dense thickets that push out native species. Given its preference for water edges, it threatens the ecosystems around water sources.
Additionally, it has an extensive root system that spreads over large areas fast, and one that threatens the stability of structures. As such, it falls under the top 100 invasive species throughout the world.
What is Japanese Knotweed?
There are many knotweeds around the globe, with some of them having invasive features such as this plant. It is woody, perennial, and herbaceous with a thriving root system. It belongs to the Buckwheat family.
Identification of Japanese knotweed
You can recognize this knotweed based on its distinctive features as follows:
The Stem
The woody stem is hollow and smooth and can be up to one inch thick. The color of the stem ranges from purple to green, with reddish-brown nodes adorning its length. Its hollow nature, coupled with the nodes, makes the appearance of the stalk similar to that of bamboos.
When fall comes, the stem dies back and remains in place during winter. When spring comes, new stems emerge from the extensive root system. While the stems are young, they have purple hues. The color of the stalk changes to green as they mature.
The growth of the stems is quite rapid, reaching three inches a day. That means that the stem can be up to a meter tall within three weeks of emergence. The stems grow together in clumps and will be up to three meters tall when mature.
The Leaves
The pointed leaves with flat bases occur in alternating positions, and they can be ovate or triangular. They attach to the stem by way of long petioles, and they can measure up to ten centimeters in width.
The Roots
The nature of the roots makes this weed quite aggressive. The root systems are large, and they account for up to 2/3 of the plant’s total mass. They are dark brown on the outside and orange on the inside.
The roots grow to depths of up to two meters in the ground and as long as eighteen meters. They can spread in all directions at a rate of half a meter each year, where the conditions prove to be suitable. Where this happens in an uncontrolled environment, they can take over a large area.
The extensive root system makes the eradication of Japanese knotweed quite challenging. You could leave a fragment as small as one centimeter in the ground, and it could give rise to another stem. As long as the fragment has access to water, there is a chance it could lead to new growths. Also, buried fragments as small as two centimeters at a depth of one meter can sprout new stems.
Control methods thus call for caution when dealing with root systems to completely eradicate them. Disposal methods are also crucial as improper disposal aids in the establishment of new plants.
The Flowers
Japanese knotweed produces white-green flowers towards the end of July or start of August. These small flowers occur in clusters, and they give rise to winged, shiny seeds with triangular shapes. The seeds are tiny, and this enables their spread through water and wind.
Not much research is available as to seed production. As such, this article will not delve into the viability or lack thereof of the seeds produced. However, you should note that Japanese knotweed has both male and female plants. The presence of both plants allows for pollination to take place, which results in viable seeds.
Most of the species available in North America do not produce pollen. They thus rely on the spread of their root networks to give rise to new stems. But where these plants establish near related species such as the Giant Knotweed, pollination can take place.
Other than the original Japanese knotweed species, there are some cultivars of this plant. It could be that you have this weed in your home, but it does not meet the above description owing to the hue of the flowers. A good example would be Crimson Beauty, which gives rise to red flowers.
While cultivars are generally not invasive, pollination by other knotweed varieties could make their growth aggressive. It is, therefore, not advisable to have any invasive knotweed cultivar in or around your home.
Japanese knotweed Look-Alikes
This invasive species has a ton of look-alikes, and it helps to note the differences between them.
The Giant Knotweed
This weed also goes by the name Fallopia sachalinensis, and it is native to northern Japan. Over the years, it has invaded many parts of the United States, owing to its introduction as an ornamental plant.
It features smooth and hollow stems with light green hues. They grow to heights of up to four meters and will remain standing when dead, like the Japanese Knotweed stalks.
The leaves feature heart shapes with wavy margins and have thin hairs covering the undersides. They can grow to lengths of forty centimeters and widths of up to twenty-eight centimeters. Blooming in this species takes place as from July, and it results in small, clustered greenish-white flowers. These give rise to small, winged black fruits. Do you see any similarities to the Japanese knotweed?
The Bohemian Knotweed
Scientifically, this species goes by the name Fallopia x bohemica. The interesting thing about this plant is that it results from both the Japanese and Giant Knotweeds. It thus exists in places where the parent plants have invaded, such as British Columbia. The bad thing with this hybrid is that it amplifies the invasiveness of the parent plants. Controlling it is, therefore, much harder than eradicating the individual parent plants.
Its stems feature reddish-brown hues and will remain standing when dead. They grow to heights of up to three meters. From the stems arise alternate leaves with lengths of up to twenty-five centimeters, and widths of up to twenty centimeters. They have spade shapes with long tips and short hairs covering the undersides. You can use the hairs as a way to tell them apart from other knotweeds.
Blooming starts in July and results in greenish-white clustered flowers. These flowers are shorter than those on the Japanese knotweed, but longer than those present in the giant knotweed. These flowers give rise to small, black, and winged fruits.
The Himalayan Knotweed
This species is native to Southern Asia and goes by the name Persicaria wallichii. It has spread to areas such as Newfoundland and Columbia and is also an invasive knotweed species.
It features red and hollow stems that remain standing when dead. They grow to heights of up to two meters, and they have alternate leaves adorning them. The leaves are long and thin and can measure up to twenty and ten centimeters long and wide, respectively. You can tell these leaves apart from the Impatiens glandifulera by looking at the margins. For the Himalayan knotweed, the leaves do not have serrations, as is the case with the Impatiens. People often confuse the two.
Blooming starts in July, and it results in pinkish-white flowers that occur in clusters. The fruits of this knotweed are unlike those of other varieties. They are small, smooth, and have three sides.
Origin of Japanese knotweed
This species is native to the eastern region of Asia. It got introduced to Europe in the mid-nineteenth century as an ornamental plant. From here, it got advertised to the public as a potential source of food for animals. As such, its distribution over the region took place fast, leading to its naturalization.
It was around this time that it got introduced to North America as an exotic plant. Here, it also spread at a fast rate, as many considered it to be an ideal outdoor plant. Many other countries also followed this pattern, contributing to its distribution across the globe.
Where can you find Japanese knotweed?
The Japanese knotweed has a preference for open sites with full sunlight and moist soils. It is not uncommon for Japanese knotweed to tolerate shade, especially near water sources. Its preference for moist soils greatly contributes to its invasion of wetland areas.
It also grows in old homesteads where the introduction is deliberate, and roadsides and forest edges, among other disturbed areas. Japanese knotweed can adapt to a wide range of conditions, which enables it to spread over vast distances. From sites with high salt content to polluted regions, this plant can survive a lot of harsh conditions.
It spreads through various means. Geographically, it relies on roads as well as waterways to spread. A good example would be where construction activities take place. The equipment used in the area could carry the roots to great distances. Horticultural trade also contributes to its spread to other regions.
Does Japanese knotweed have any uses?
This species grows at a fast rate, and this makes it an ideal source of energy. However, studies on the same showed that such activities would be economically unviable.
Economic
There were early reports that Japanese knotweed could serve as a source of biofuel. However, the viability of this proposal is yet to show.
Social
Some people rely on Japanese knotweed for food, given that it tastes a lot like asparagus. Additionally, it has medicinal benefits and can alleviate symptoms associated with dermatitis and hyperlipemia, among other ailments. The root fragments have tons of resveratrol, which is an anti-cancer drug.
Interestingly, most of the resveratrol supplements available in the market come from these roots and those of the sachalinensis. This extract is so potent that it has exhibited anti-tumor effects in mice.
Environmental
This species flowers a lot, thus providing value to bees and other insects. However, in some regions such as the UK, Japanese knotweed does not produce pollen. But where it flowers, apiarists have recorded significant increments in hive weights. Additionally, this plant stabilizes soil in steep slopes and along water sources. It can thus come in handy in places at risk of soil erosion.
Japanese knotweed threats
The built environment has borne the brunt of this species, which weakens structural foundations. Here are some of the ways this knotweed has spread and the effects of this:
Dispersal
This species does not rely on sexual reproduction and instead spreads through the use of root networks. While this is a passive method, it has worked in favor of this plant as it is aggressive.
Natural
Where Japanese knotweed establishes near a water source, movement of the water can break off some parts and move them downstream. Here, they can establish, and owing to suitable conditions; they can spread fast. Floods often facilitate the spread of this plant.
Accidental
Most growths in the present day are as a result of unintentional introductions. Where people fail to observe disposal guidelines, they leave the fragments out in the open, where they can get distributed. Also, mowing the plants near water sources or moving infested soil is not advisable. Soil must get checked for any fragments. Infested areas should be free of disturbance until the knotweeds get eradicated.
Intentional
In the past, many people looked at this species as a desirable ornamental plant owing to its exotic appearance. They also cultivated it as a means to stabilize the soil. To date, some people still use it in their homes, for lack of knowledge as to its effects.
Japanese knotweed effects
Environmental
This weed spreads at a fast rate and takes over riparian habitats by forming dense thickets. In this way, Japanese knotweed limits access to sunlight, thereby starving native species of the necessary nutrients. Additionally, it forms thick mats comprising decaying vegetation during fall and spring. And this further shades out the native species in the habitat.
Where this weed establishes in an uncontrolled environment, it can wipe out all the native species over time. There have been claims that this species has allelopathic properties that inhibit the growth of other plans. Research as to the truth behind this is ongoing.
With native species reducing in numbers, biodiversity faces a threat. A knotweed monoculture cannot support the same number of animals that native species would. As such, animals migrate to other areas, leaving the land’s natural ecosystem altered.
While people have often used Japanese knotweed as a means of erosion control, it is not as effective as native species. Its roots spread out while those of native species are dense. As such, where the knotweed grows near a water source, it leaves the bank vulnerable to soil erosion. Breaking of banks and the flooding of surrounding areas is thus a possibility.
Economic
The built environment is at risk owing to the spread of this plant. Japanese knotweed has an aggressive root system that can grow through concrete and asphalt surfaces up to eight centimeters thick. That means that it can affect the stability of foundations, posing a risk to the inhabitants.
The UK is one such region where the effects of the knotweed have been seen. As such, the regulations call for eradication and disposal of the weeds before construction.
Where this weed establishes, the value of a home reduces significantly. UK mortgage lenders have resorted to denying lending to properties with knotweed infestations. As such, developers, as well as homeowners, have incurred losses regarding property values.
Also, it costs a lot of money to keep this weed from spreading. Take the example of Wales. One county council spent as much as six hundred thousand dollars in 1994 to eradicate this weed. Reports show that it would cost as much as three billion dollars to control this weed species in the UK at present.
For one hectare, one needs at least ten thousand dollars to cover the costs of a three-year treatment. This figure assumes that you would spray the land twice, and it does not cover the expenses of re-vegetation. Where construction is taking place, developers often have to add as much as ten percent to the budget to account for control measures.
Social
This weed forms dense monocultures that can block one’s access to water. It thus becomes difficult to engage in activities such as boating and swimming in affected water sources.
Furthermore, this species can be a fire hazard during the dormant season owing to the drying of its stems.
Having Japanese knotweed in your outdoors or another area would thus pose a threat to the environment, your finances, and society, as shown.
Japanese knotweed management
How do you manage an invasive plant such as Japanese knotweed? You do so by employing integrated management practices. In this way, you can deal with knotweed infestations and reduce their negative impacts on the economy, society, and the environment.
When choosing a plan, you should choose one that offers integration, as it is more effective. You also need to consider the state of the site and the nature of the knotweed when choosing control options. It helps to note that leaving the land bare after eradication could induce further growth. Thus, replanting native species is of the essence.
Management starts with the identification of the knotweed before developing a plan. You should consider the size of the infestation, its likelihood of spreading, the accessibility of the infestation, and the risks it poses. While you are at it, you should think about the presence of native species, water sources and wildlife, and ways in which the control measures could affect these.
Having a record setting out the plans in place with an overview of the infestation is necessary. It allows you to stay on track as you employ diverse methods to eradicate the infestation.
Where an infestation has established, the priority should be in preventing its spread. You can do this by isolating the infested area. The reason behind this is that knotweeds take a considerable amount of time to get eradicated. Some infestations may take you up to ten years before you can see positive results. As such, it would be best to control the spread to reduce the time taken in control methods.
It may look like a lot of work, but it will be worth it in the end. Developing a long-term strategy will work in your favor, and this article will delve into critical considerations for this undertaking.
Natural Resources
The control methods of your choice should be in line with the relevant laws in your locality. Suppose you have endangered species in your yard, you should choose an approach that would protect them. You must conduct an assessment of the likely outcomes of each method. You can consult the relevant authority to help you in deciding the best way forward.
Start by prioritizing the control of the knotweed to avoid its spread to other areas. That should be key in your management plan.
Here is how you can do this.
Where you do not identify any knotweeds in your land, you are in luck as you can avoid the associated costs. However, you should protect your yard from any invasions by regularly monitoring the species. In this way, you can act fast when there is a need for the same.
Where you come across an infestation, there are two ways to go about this. It all depends on the age and size of the infestation.
For a small outbreak, you will not have a lot of established Japanese knotweed in the land. You should thus start by focusing on the spaces with endangered species. In this way, you can eradicate the knotweeds before they spread. You can then assess the need for restoration efforts. In some cases, the infestation is so small that the land can regenerate without human intervention.
Where the infestation has been around for a while, the population of knotweeds is likely to be high. As such, you will need to dedicate a lot of time and money to control measures. Start by assessing the presence or lack thereof of protected species on the site. Also, think of the current use of the land. Are there features you would like to protect?
If there are endangered species or essential features on the land, you should focus on protecting them. You can do this by working on small populations at a time, working from the outside heading in. Where there is no need for protection, you can work on preventing the spread of the weed on the pathways.
As you do this, you can assess if the methods are working and if there is a need for more resources. Once you eradicate the weed, you can work on restoring the site where necessary.
Creating Emphasis
It is always best to protect sites before knotweeds become invasive. That includes natural resources such as forests that are at risk of invasion. And you can do this by monitoring the species in an area. Where you come across a new infestation, work on protecting the environment. You should also protect the available resources in the absence of an invasion. You can get a list of endangered species from the local authority to help you with this.
Where you come across an infestation, start by working on the small populations on the outside. You can then work heading in as you expand the un-invaded site. Reports indicate that this weed can have a lag time of up to forty years before it becomes aggressive. Dealing with it promptly is, therefore, of the essence.
The need for restoration
Some sites will require restoration, while others can regenerate by themselves. You can assess the need for the same by considering several factors.
One is the disturbance at the site. Suppose there was a high population of knotweeds in a disturbed area, such as a forest trail. In this case, you would need to work on restoring the area as disturbance could yield new growths.
Two is the nature of the knotweed. Some species leave seed banks behind, which is not a cause for worry with this weed. In this case, you need to think about the presence of root fragments and the chances of re-sprouting. It is in your best interest to completely eradicate Japanese knotweed before restoring the site.
Three is the chance of re-infestation. Here, you will not only consider the knotweed but other invasive species as well. Look into the species growing near the site and their pathways of introduction. You might need to restore the site where there is a risk of invasion by other weeds.
The final note would be the existence of native species. If any are present, consider their ability to regenerate following the control measures. It could be that they need some help to regain their health. What can you do to help them in regeneration? Where no species exist, what can you plant to restore the site and protect it from invasions?
Regeneration would enable you to save money used in restoring the site. But where it is not possible, you can restore the site by planting species in it.
Now that we have covered the general considerations when employing management methods, here are the measures you could use:
Prevention
The good news is that you can prevent the spread of this weed, thereby reducing the costs associated with the control methods. Everyone can be a part of the management program in the following ways:
Reporting
Where you come across a plant with the features of Japanese knotweed, you should map out its location. You can then share this information with the relevant authority as well as your neighbors. Where you are unsure of the nature of the plant, take a picture of it and forward it to the concerned authoritative body.
Education
Many people have come across this weed but are unaware that they have done so. It owes to the lack of adequate information as to its characteristics. By taking part in community programs, you can be part of the change by spreading much-needed information. In this way, people can watch out for invasions in natural and disturbed areas.
Limitation of Disturbances
Where there has been an invasion, you should work on avoiding the area until the weed gets eradicated. That means you should remain on the marked paths to prevent further spreading Japanese knotweed. If you visit a forest or other natural area with invasive species, stay on the trail.
Once you leave an infested area, check your shoes, clothes, and machinery for any plant parts. You can clean the cars and equipment used on the site to prevent the spread of fragments. In this way, you will not spread this weed to un-infested areas.
Where native species have established, allow them to continue growing, unless you plan to have others in their place. Leaving the ground bare exposes it to invasions by weeds such as this.
Avoidance
Many invasive species spread aggressively owing to cultivation in non-native regions. You should thus avoid using this knotweed, or other invasive species in your yard. Where you want to stabilize soil or reap ornamental benefits, there is an array of native species from which you can choose.
If you come across a garden center selling this weed, be sure to educate them on the impacts of this species. The same goes for your family and friends.
How to control Japanese knotweed
Control methods use up a lot of time and money. Ideally, you should have eradicated this species within five years. However, the site conditions may affect this period, thereby lengthening it. The control measures are not a one-time thing, and they call for consistency. If you use a measure once, the disturbance will stimulate the growth of new plants. It would be worse than letting the weed be.
Once you eradicate this weed, the next step should be to replant native species in the bare ground. Regeneration is possible, and this depends on the extent of the infestation. If you leave the soil bare, knotweed or another invasive species could spread over the area. Below are the current control measures, guaranteed to offer you results.
Manual Means
Cutting
If you work on cutting the stems monthly when the knotweed is in active growth, the root systems weaken. The weakening owes to the depletion of the food reserves in the rhizomes. Note that you should continue doing this for at least five years to adequately deal with this weed. If you want the best results, you should integrate the cutting with herbicide applications. This technique works for both old and new infestations and is time-consuming as well as labor-intensive.
Digging
Where the invasion is relatively new, you can dig out Japanese knotweed as they have a shallow root system. At this point, you can get hold of the plant and the roots and remove them from the ground. Note that you should remove all the fragments as small pieces could result in re-sprouts. You can work on the infestation by section to ensure that you do not leave out any areas.
Once the knotweeds are no more, you can restore the site by planting native species on the land. The disturbance accruing from the digging could lead to the establishment of invasive species.
Physical invasive plant removal is labor-intensive
Excavation
For some populations, digging and cutting will not suffice, more so when the Japanese knotweed are mature. In such a case, you can rely on the use of an excavator. This method is quite common in the UK, mainly with developers, owing to its speed. You start by creating pits as deep as five meters or more and removing infested soil up to a depth of two meters. You then move the infested soil to the pits with root barriers in them.
In some cases, burying the knotweeds on the site is not a feasible idea. In such a case, you can move the fragments and soil to a landfill. Be sure to check with the relevant authority as to the legality of this in your area.
Cultural Means
Grazing
The good thing is that some animals will feed on new foliage as it emerges towards the start of spring. Horses and cows, as well as goats, can work on reducing the number of young shoots. Note that they will stop feeding on the Japanese knotweed once the woody stems develop. As such, this is not a permanent solution, as it only works in suppressing the growth of the weeds.
Using grazing in combination with another method, such as chemical application, will give you the best results.
Tarping
Have you heard of this term before? It involves covering the knotweed with dark material. In this way, the plant will not have access to light and will roast in the heated conditions. You should start this process towards the end of spring and keep at it throughout the growing season. It only works in places with high light conditions and can work for both medium and large invasions.
Start by cutting the stems before covering them with dark and heavy material. Ensure that the knot is not too tight as this could break off the stem and lead to subsequent growths. Though the tarp should be loose, it should be heavy such that it cannot get blown away.
You can use tent pegs for this as they will not take up much space and will allow access to light. The option used will depend on the site conditions. You should use some barriers around the invasion as the weeds will try to spread in search of light.
Having met all these requirements, you can leave the tarp in place. It should remain on the plant for an extent of a full growing season. Even then, you should let it stay on the plant for at least three seasons. If you remove it earlier than this, the root systems will be aggressive in spreading.
This method calls for a lot of labor, which could run up the costs of controlling the weed. You need to monitor the tarps to ensure that plants do not grow through them or under them. Where tears occur, you need to fix them immediately. Failure to do so will allow the plants access to light and air.
Combine this method with another control measure for faster and more effective results. It is important to note that tarping affects the soil. As such, when restoring the site, you may need to add some soil fungi to facilitate the growth of other plants.
Chemical Means
Herbicides work great in controlling the spread of knotweed, more so when used in combination with other methods. For your safety and that of native species, you should adhere to the herbicide label. You should also check with the local relevant authority as to which options are suitable for your site.
Timing
Timing is everything when it comes to herbicide applications. It affects how well the chemicals get absorbed, and it protects native species in the vicinity. You should start the application towards the end of May. Let the chemicals sit on the plants for a while before following up with another application when summer starts. In early July, another application will be necessary to deal with re-sprouts. You could also have missed some patches in the first application, and this will deal with thriving plants.
For small infestations, you can rely on chemical applications alone. However, the same does not hold when the infestations are widespread. For big plants, you will get better results by combining herbicide applications with manual means. You can continuously cut the plants each time they grow to full height, as this will work in weakening the root systems. After several cuttings, you can now use a chemical on the plants to effectively eradicate them.
For large infestations, combing herbicide applications and manual means will give you results in a few years. It involves a lot of repetition. For small populations, you can rely on herbicide applications.
Foliar Application
Here, you apply the chemicals directly on the foliage. The label of your chemical of choice will act as a guide as to timing and procedures. For small infestations, you can rely on spray bottles. For large areas, a backpack sprayer would enable you to cover the land at a fast rate.
Wick Application
Foliar applications work for lands where there is no risk of affecting native species. But where there are desirable species on the site, wick application would be an ideal method. It involves directly applying chemicals on the leaves of Japanese knotweed. As is the case with foliar application, the method of choice will depend on the label instructions.
With chemicals, you have to consult with relevant authorities to ensure that you abide by the law.
Biological Means
Biological control relies on invasive species’ natural enemies to fight their growth and spread. It is an easy way to protect the ecosystem in which an invasive species establishes. At present, research is ongoing regarding biological agents that can be effective in eradicating the knotweed.
Disposal
Improper disposal is one of the leading dispersal methods. As such, once you cut or use chemicals on plants, you have to dispose of them in the right manner. The first thing you need to note is that composting is not an option. For many people, composting would serve as a means to add to the nutrients in their land. However, this will not hold for the knotweed as the conditions created would enable it to thrive.
Take all the plant materials and stuff them into thick dark plastic bags. Preferably, the bags should be black, as these would absorb the most heat. Tightly seal the bags to ensure that no air can get in, then leave them in direct sunlight. You can leave them for a week or more, as this will allow the stems and roots to dry.
You can then send the bags to a landfill or burn them. In this way, they cannot sprout and wreak havoc in your land.
Restoration
Once you eradicate the knotweeds, you need to come up with a restoration plan. Leaving the ground bare will only encourage the growth of other invasive species. Restoring a site leads to a healthy ecosystem that can resist invasion by undesirable plants. You will need to monitor the site to ensure that native species establish and to remove any invasive plants.
During Eradication
You do not have to wait until you completely eradicate the knotweeds to start working on restoration. Here is what you can do as you fight this weed:
Mulch
Having mulch on the ground has proven to be effective in preventing the growth of invasive species. It reduces access to light, which works in favor of native species with tolerance to shades. Thus, native species can fill the gaps left as you remove the knotweeds.
Seed
After using a control method on the site, work on seeding the area with a desirable crop. A good idea would be an annual cover crop as it can take over the area and prevent invasive species’ growth. As the plant establishes, it will reduce the chances of invasive species re-sprouting.
After Eradication
When your land is finally free of this invasive weed, you will need to ensure that it remains as such. Note that you can only start these restoration practices once you fully eradicate the weeds. Else, the disturbance will lead to knotweed re-sprouts and will affect the growth of the native plants.
Rehabilitate the soil
Japanese Knotweed is thought to have allelopathic effects on the environment in which it establishes. As such, the soil conditions may not support the growth of native species. You would thus face a problem with other invasive species taking over the land. The best way to avoid such a situation would be to alter the soil chemistry in favor of desirable plants. That involves increasing mycorrhizae levels in the soil once there are no more knotweeds on the site.
You can do this by using logs, sticks, and leaf mulch, which will add nutrients to the soil. These elements will also work in providing cover to encourage the growth of native plants. You should also reduce soil compaction on the site.
There are many mycorrhizal products available for sale, both online and in local gardening stores. You can take advantage of these when replenishing the soil.
Using Natives
When planting natives, you need to consider the risk of invasiveness on the site. Where there are none, you can choose from a variety of native plants. Where there are invasive species that could take over the land, you should use large native plants. In this way, they can compete with the germinating seedlings and weed them out.
Conclusion
Having knotweed in your home provides a threat to the stability of structures, biodiversity, and ecological balances. It is thus best to prevent the growth of this weed. Where it has established, control measures should be in full gear to prevent further spread of Japanese knotweed.
