Weeds are often thought to be harmless, but did you know that certain types of weeds can grow into trees and could destroy your yard? That’s right, Japanese knotweed is not just an ordinary weed that’s going to come and go.
Once it grows in your yard, it will begin growing into a gigantic tree that will spread its roots wide across the ground and suck up all the nutrients in the soil. It is essential to get rid of this plant before it gets out of hand.
Here, we’ll look at how to identify Japanese Knotweed and then some tips to control and kill Japanese Knotweed in the easiest possible way, following these steps will ensure you control this weed and stop it from taking over your garden.
Some have even gone as far as to use diesel to kill Japanese Knotweed. Which I don’t advise.
What causes Japanese Knotweed Growth?
The main cause of Japanese Knotweed is the arrival of the plant in a garden. The plant arrived in the UK in the 19th century and it was initially seen as being an aesthetically pleasing ornamental plant and was used to fill gardens. It is one of the most common weeds that look like small plants.
Whilst this is a contributing factor, many other factors can result in a Japanese Knotweed infestation.
6 common causes of Japanese Knotweed Growth
- Rhizome dispersal – is the main cause of knotweed growth in gardens. Rhizomes are stems that run underground and can be very long; one stem can cover many square metres. Rhizomes can be dispersed by machinery, animals or humans if they come into contact with them.
- Looks Like Another Weed – Another familiar cause of Japanese Knotweed is that people simply don’t know what it is. Knotweed looks like bamboo and can be used to make furniture and other products. Untrained contractors may even use it as a building material without knowing the risks they are taking on. This means that knotweed can spread into new areas quite easily, especially if people place infected soil or materials in the skip or dump their contaminated waste illegally.
- Not Paying Attention To New Growth – Not carrying out regular checks, especially after rain or when digging the garden over. If any fragments are found you must make sure you do not transport these fragments to another area of the garden or anywhere else for that matter.
- Birds Bring In the Seeds – The next purpose for this invasive plant to pop up in your garden is that you have a bird feeder, and the birds eat the seeds, which they then deposit elsewhere in their droppings. One of these places could be your garden, especially if you have any shrubs or trees. If you notice Japanese knotweed in your garden and know that you also have a bird feeder, make sure that it does not contain berries from this plant! For example, do not offer it to blackbirds as they are known to be very fond of these berries
- Constant Checking During Winter – Leaving plants to die off naturally during the winter months, this will encourage the spread of the plant as dead material will easily break off and be transported by wind or other means, it is important to carry out checks regularly throughout the year and if you find any evidence then dispose of it carefully.
- Neighbors have the weed in their yard – Final reason could be that your neighbor has knotweed growing on their property and it has grown into yours. Should this be the case, then you should speak with them about eradicating the problem immediately before any damage is caused to your property.
Where does Japanese Knotweed Grow
Knotweed is a resilient, invasive weed that can grow anywhere that has enough sunlight and water. Its roots (known as rhizomes) can reach a depth of 3m and 7m horizontally. The soil can be compact or loose, acidic or alkaline, fertile or poor quality. Knotweed grows well in most soils except peaty or dry soils.
Japanese Knotweed is often found on roadside verges and waste ground where its vigorous growth can create dense thickets crowding out other plants. It can also be found growing beside rivers, streams, ponds, and lakes where it has been spread by flooding.
It grows well on disturbed ground where there are gaps between buildings or in un-managed brownfield sites, railway embankments, and utility areas. It is often found growing along roadsides – Japanese Knotweed gets everywhere by the distribution of stem fragments in gravel used for road construction.
When should you treat Japanese Knotweed?
Japanese Knotweed is a fast-growing invasive weed. There are 3 key times of the year that Japanese Knotweed should be fed to ensure its eradication and destruction.
Spring
The most critical time of the year for effective treatment is Spring when the plant first awakens from its winter dormancy and before it starts flowering.
It is at this time that you need to make sure your weed killer fully penetrates the plant’s rhizome system (underground stem network) to kill off all parts of the plant. If you only kill off some of the rhizomes then new shoots will regrow from those which remain.
Autumn
The second key feeding time is Autumn, just before the plant dies back for its winter dormancy. As with springtime, if you miss this opportunity then any rhizomes which were not treated during spring will regrow next season as new plants.
Summer
On established sites applying a herbicide during the summertime can be helpful as it will help to weaken the plant ready for treatment in Spring and Autumn. In any case, on established sites, treatment will likely require multiple years of herbicide application to destroy a Japanese Knotweed infestation.
How To Treat Japanese Knotweed
First off, you cannot treat Japanese knotweed yourself if you are not familiar with how this weed spreads.
Japanese knotweed growth can be very invasive and must be treated using specific methods to ensure its destruction. These methods are not something that a DIY enthusiast or gardener can carry out successfully.
The reason it is so important to use a professional to deal with your Japanese knotweed problems is that they have the knowledge and experience to ensure that the plant is fully eradicated and will not grow back.
If you try to treat it yourself, there is a high chance you may cause more damage, because you may spread the rhizomes in the process or even accidentally transfer some of the plants to another area of your garden, or even further away from your property.
How to Remove Japanese Knotweed without chemicals?
There are several ways to killing Japanese knotweed. The most common method is spraying with herbicide, although many people do not like the idea of using chemicals in their gardens and near their homes, especially if they have children or pets.
There are solutions, however – you can get rid of Japanese Knotweed without chemicals. These include :
Deprive it of light
It’s essential to cover the Knotweed with a layer of heavy black polythene and then cover this with a thick layer of compost, rubble, or soil. The larger the area you can smother, the better your chance of success. If you’re lucky enough to have an old shed, greenhouse, or similar structure lying around that you could use to create a temporary roof over the top of your polythene and soil covering, all the better.
If you don’t have any poly-tunnel or other temporary structure available to put over the top of your polythene covering, then you could also use a tarpaulin with bricks placed on top to help hold it down.
For best results, try to keep this coverage in place for at least 2 growing seasons if possible. If you’re using polythene and tarpaulin that let light through in any way, then ideally keep the covering in place for 3 or more growing seasons if possible.
Physical removal of the plants and their rhizomes (root systems)
This method will not work if there are more than 10 plants in an area, though, because they will simply regenerate themselves after being removed. If you have fewer than 10 plants, it’s still worth trying as long as they aren’t growing next door or on your neighbor’s property (which could lead to lawsuits).
Dig out as much root as possible
The next step is to dig out as many roots as possible. Try not to leave any behind, but don’t panic if you can’t get everything out. Use a strong fork and spade and dig around the edges of the knotweed patch until you can see where some of the roots have broken off underground.
You’ll need to get down at least 2 meters (6 feet), and 3 meters (10 feet) is better. There’s no point in digging too deep because these roots stretch further than that!
Grazing
Animals can be used to keep plants in check by regularly grazing on them. This is a very useful method of control but it may not be practical for the average garden owner.
Another option is using goats, which have been used effectively in some cases. In both instances, the control has to be carried out over several growing seasons, and the area may need to be fenced off from other plants that you do want.
Best Herbicide for Killing Japanese Knotweed
Killing Japanese Knotweed is easily killed using the Monterey Tree Stump Killer herbicide. For more than 25 years, it has been one of the most popular products on the market because it is exceptionally successful at killing Japanese knotweed and other weeds.
- CONTROL WOODY PLANTS - The Brush and Vine Killer is ideal for control...
- BRUSH AND VINE CONTROL - Not only can this product be used for stump...
- CONCENTRATED FORMULA - This product comes as a concentrate and will...
- OUTDOOR RESIDENTIAL USE ONLY - This product is designed for outdoor...
- NOT FOR USE ON EDIBLE CROPS - When applying the herbicide, avoid drift...
When used as directed, Monterey Tree Stump & Weedkiller is an extremely potent liquid concentrate that kills plants and weeds at their roots, ensuring that they won’t return. Grass and weeds in your garden can be easily eradicated with this chemical mixture, which penetrates deep into the root system and does not harm neighboring plants.
There is no need to chop down or dig out stumps before using this product because it works year-round and on any size plant, from little weeds to big trees. You can use this chemical weedkiller on lawns, flowers, and vegetables as long as you follow the directions and keep it out of the reach of children and dogs until it dries completely.
Features:
- Destroys all green plant matter including trees, stumps and roots
- Leaves no harmful residue
- Kills woody weeds in minutes
- Rainproof in 30 minutes
Roots of dead or cut trees can be killed by using this herbicide, the active ingredient is triclopyr and penetrates through dead tree bark. Get rid of undesirable stumps and bushes using this product. With any Roundup sprayer, you may apply this stump killer.
Make sure to wear long-sleeve shirts, long pants, shoes, and socks while using this item. Avoid skin, eye, or clothing contact. After handling, wash hands thoroughly in warm soapy water. Prevent access by children and pets.
Because it’s hard to come by, we recommend purchasing it from Amazon, where you’ll get the best deal and free shipping!
- CONTROL WOODY PLANTS - The Brush and Vine Killer is ideal for control...
- BRUSH AND VINE CONTROL - Not only can this product be used for stump...
- CONCENTRATED FORMULA - This product comes as a concentrate and will...
- OUTDOOR RESIDENTIAL USE ONLY - This product is designed for outdoor...
- NOT FOR USE ON EDIBLE CROPS - When applying the herbicide, avoid drift...
FAQs
Will salt kill Japanese Knotweed?
Salt is used to a lesser extent than herbicide but it is effective on Japanese Knotweed. It takes a long time to be effective, however, and can be very costly. Also, it can damage the environment and you will need a large quantity of salt.
Does Vinegar Kill Japanese Knotweed?
Vinegar doesn’t kill Japanese Knotweed. In fact, the use of vinegar can make it worse! Vinegar is a very weak acid and Japanese Knotweed is highly acidic so they don’t affect each other. Also, if you apply vinegar to your Japanese Knotweed plant, it will translocate the chemicals down into the rhizome which will then make it grow even faster.
Resources:
- https://dnr.wi.gov/topic/invasives/documents/japanese_knotweed_control.pdf
- https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_017951.pdf
