9 Common Mistakes To Avoid in Trying to Control Invasive Knotweed 

Thank you for this concise and well researched video! I discovered we had a small batch of knotweed by the side of our house and went into an internet rabbit hole of doom. This video made it clear what needs to be done and the persistence it takes to eradicate this Darwin winner. I both admire it and fear it.

I got rid of all my knotweed, dug it up, and burnt it all up. It still came back, but just a few shots, just kept poisoning it. After 3 years, it was finally gone.

I love you. I’ve made many of these mistakes in my years-long battle with knotweed along my house, but I’m not giving up yet! The challenge now will be letting it grow until fall when I hate its guts so bad.

I have this thing about 6m2 at my property in Ontario and just found out what this nuts thing is. I Dug it out this weekend hard with pick and followed the roots going and what I found interesting, it nested below concrete stairs fundaments.I am south Europen and this thing have the Same rooting as a fig tree.Exactly the same but way more invasive. They like wet concrete or stone deep underneath. Wet and safe from anything. It is impossible to kill it without removing the base of the concrete where the root Is hiding. Luckily I bough this property after fire destroyed and that fundaments will be gone. Just my experience. I will treat with herbicide in the fall and keep you posted. All the dug out roots I will burn in the metal barrel, bit by bit. What a crazy plant.

1. Don't mow it - it will only help the spread! 2. Covering it with a tarp doesn't work without extensive other layering strategies 3. Dont use herbicide early in the season - wait til fall (so the weed draws the herbicide down into the rhizome) and be sure to do it before a frost & 4. treat with herbicide twice. 5. Cutting in the summer only helps spread it !! 6. The year after first chemical treatment 7. Plant native plants 8. Knock down all dead stems the season before fall chemical treatment. 9. Worst mistake is to do nothing.

Excellent video and explanations. Confirms research that I've seen in gardening groups about the best way to tackle knotweed. Since it's a plant that evolved in volcanic conditions, its ability to recover when almost completely destroyed is quite impressive. I wish states had better official procedures, I've felt physical pain the times I've watched a mower mowing the edge of highways contaminated by knotweed, knowing that it's only going to spread... Same thing with people covering, the underground network of the plant is much larger than you'd expect and it will spend all of it's energy till it finds the edge of the covering, and then it will pop up and continue happily.

Great video, I had a large stand of knotweed, sprayed it twice every year starting late summer/early fall (with 4oz of 41% glysophate mixed with 1 gallon of water). Killed 80% the first year, most of the rest the second year. this spring I found three little plants, they will be sprayed in the fall. Green shoots is correct, follow his advice. P.S. Don't mow it, don't cut it, you'll spread it all over the yard!. Kill it first.

I left a invasive plant sit on concrete block for 3 years and it never died after that I burned it in barrels. Some species are highly highly invasive

This is one of the most comprehensive and well informed videos on knotweed treatment on this platform, thanks for uploading! My quite large patch of knotweed just received its first foliar spraying treatment, after it was very hard for me to just leave it alone for all of summer. I set up a camera to do time lapse videos of the herbizide effect and regrowth next season. What I was asking myself: Soon, the upper parts of the plant will have died of. The rhizome is probably not yet in full dormancy (mid october), but already weakend by the herbicide treatment. Would it make sense to carefully dig free some of the bigger sections of the rhizome and drill vertical holes right into it to fill them with concentrated glyphosate? Idea is that it is translocated all through the not yet dormant rhizome? Anybody ever tried that?

There's a new invention called Rootwave in Europe, but unfortunately, it could be many years before it's available in the U.S.

We're into our 4th year of Japanese knotweed eradication; we started the year we bought this place. No herbicides were used. My wife played the role of excavator. Bless her heart, she dug more than I could have imagined at the beginning. We knew it was not going to end the stuff but we decided to get as many rhizomes as possible. Our Knotweed was in a section where filled land transitioned about 8' down to the natural ground level. The patch is shaded well so not much else grows back there. It is 140' long and 30' wide. The fill work was done in the 1970's. I don't know if the knotweed started then or sometime later. Year 2 we finished the excavation including a trench all around it to establish a boundary. We double tarped the trench and backfilled to level. Then the entire area was tarped. We taped all of the seams. All told we had two pickup loads of rhizomes and crowns. We bagged and sent them to the landfill. Year 3: The knotweed has now had almost no sunshine for 2 years. We rolled back the tarps and found the most vital remaining rhizomes and dug them out....replaced the tarps and remained vigilant, digging out any new sprouts around the area. We've only found a handful...but just ONE is too many. This was year 4: We rolled the tarp ack and found very little regrowth after 3 years with no sunlight. We covered the entire area with another very heavy duty tarp. Next year is year 5 and we'll be adding a layer of bark mulch. We didn't want to do that in case we had to back-track....because this stuff is unbelievably resilient. We only found two stray sprouts this year...feeling pretty good about it so far.

Knotweed sucks... but in my opinion, mugwort is worse. It stinks and isn't fun to break in half like the knotweed.

or just allow the deer in. my deer here in n. idaho eat them and keep them from getting out of hand.

When I built my house a contractor had some loam delivered and it was full of knotweed roots and chunks. Took years of spraying, and digging to get rid of it all. Nightmare. Worst weed ever.

Great information. I’ve been battling my JKW for over 20 years. All of my recent research aligns with your video so I am ready to attack it correctly this year!

Thanks for this video! 2 questions 1. Do you have any thoughts on stem injection vs foliar application? I have a patch of knotweed about 500 sq ft in my backyard, and I'm trying to plan for the most effective possible herbicide application, even if it takes days. 2. I just bought this house -- I know the previous owners were very against herbicide treatment. Most of my knotweed is localized to the edges of my property, but there are individual straggling crowns toward the center of my lawn. Is it better to let them all grow so that the herbicide treatment in the fall is maximally effective, or is it possible / advisable to remove the rhizomes from these straggling crowns in the center now so that I can use that portion of my yard?

This is the best video that I have seen on this subject. Thanks!

In my thinned stand ( injected the blue last fall), decided this spring to not wait on them as I pulled the garlic mustard. In late April, zone 7, after some rains, as strong shoots come up, I find that gripping the stems close to ground level and applying a steady pull can result in getting a lot of rhizome out with the stem. Then bang the earth clump a bit and leave it sitting on a nearby log to dry out. Maybe revisit another day to knock out some more earth for more drying. I dry the garlic the same way. Those that can't be pulled will be candidates for the blue in the fall. Have not seen any mention of this pull and dry method

What if you cover with concrete?

Great video! Covered everything one might need to know about the process. I have tried everything except herbicide at this point. 2 years into attempting to clear a 3/4 acre of knotweed in my yard. Started with making paths through, then removing dead shoots, then burned them. Starting to make progress with digging up clusters. Will try herbicide treatments this fall. Hoping to be able to get some use out of my yard one day!

Thank you for this overview! If a few small knotweed shoots come up in spring after a previous fall treatment, would you recommend digging the crown out or letting it grow to re-treat with herbicide next fall?

Hi there - thanks very much for your video. I have a small infestation of around 4 stems in a very coveted part of London. I poisoned about 5 years ago and this is the first I’ve seen of it since its last treatment, the neighbours have built a wall and disturbed the ground which is why I think it has returned. When I treat this new growth, should I dig it up after the herbicide or should I leave the soil alone? I don’t want it to spread to the neighbour. Thanks!

Excellent information. I have had a lot of success treating small patches using stem injections but if it returns I will try treating it later in the year. Thanks

After following your advice and treating my large knotweed stand twice in late automn, I seem to have good results. Untreated patches on properties in my area are already showing lots of knotweed groth. On my land, there's almost nothing visible. I do have some isolated, small shoots coming up here and there. I started to dig them out. However they do come up in areas where they're not close to the big woody crowns of past seasons but more on the side. When I dig them out, the roots don't seem to connect to a large crown or big rhizom. So I am not sure where / what do dig up. Check all seemingly inactive crowns from past seasons for buds? Dig out all remote stragglers? Both? Thanks for advice, already quite some progress made over here.

How do i avoid mowing it when its all over the middle of the lawn?

I've been dealing with a couple sizable JKW patches in my backyard for the last few years. re: digging up crowns, I've read that you should disturb the ground as little as possible because it only encourages growth. Is that not true prior to spring when it may still be dormant?

We have knotweed in the backyard but we have a small child and don’t want to use herbicides. Are there zappers that work for knotweed or other less toxic methods?

Im in NH and have this EVERYWHERE on my property... i ended up excavating a big area of it but it is going back mightily already. If i want to treat it and you say late fall maybe 2 weeks before first freeze... when would be a safe time to start treating... October?

Why not just dig out the rhizome if you don’t mind the physical labor?

Bravo.......... knot weed.........I grow not grass............that's sound like nut and chocolate stuff......cheers

Here is a link to the source material shown at 1:30 from the New Hampshire Department of Agriculture: www.agriculture.nh.gov/publications-forms/documents/japanese-knotweed-bmps.pdf

Great video! Concise and to the point. I just moved into a property that was hugely neglected and I have two stands of knotweed! Never heard of it till now. This video helped so much, I was cutting them down and planned on mowing. What an ugly plant ..just why...

Adhoc using these supplies in summer 2 years back injected to stems 3 in from ground seemed to have good kill. Left with smaller population of stragglers. This fall did before frost, more systemically throughout the grove, also did injection, anything bigger than a thumb diameter. Want to knock back the clumps with 4-6 massive stems. Will see come springtime

Knotweed is a medicinal super food it has helped greatly with that my recent bout of Lyme disease.

I just bought a new house with new sod, which I thought would be my only worry. The backyard came with a tiny downward slope in the back covered with mulch and some newly planted Emerald Green Arborvitae ‘Smaragd’ shrubs. Within a week, Japanese knotweed has appeared through the mulch and has grown about 2 feet. A handful have started to sprout through the new sod. I haven't mowed yet but have been watering it. Now I'm trying to figure out how to maintain the new sod and combat the knotweed simultaneously, and I'm paranoid about mowing. Before each mow, should I cut each stem as low as I can and immediately discard? I know herbicide is supposed to be applied in the fall, but what about for cut stems in the spring and summer if I have to mow? I also don't want to encourage the rhizome to grow horizontally under the sod toward my house looking for new places to grow, so feeling paralyzed here. As for the knotweed growing through the mulch, should I just leave it alone until fall? A few other government resources recommend cutting just the first week of June. Also I saw a video of yours from 4 years ago where you cut the stem and apply the foam there. Do you recommend just applying foam to the leaves now? @Green Shoots

Nice and informative video. Now I know much better how to go from here, but it will not be an easy task. Late last fall we started to pull down a lot of JKW (a little part next to a road, that unfortenately belongs to our land - a bit from the normal one). There are now few new greens coming up, looking much better. We have never done anything, but the next buy neighbour could have done someting 10 yrs ago (it is on their land too). The first part was ok, but not the spraying last weekend (we'll do nothing more until late fall). But we also have municipality people with their rules, taking no consider -the want the sight to be clear for cars. Right now only wish we had some (blue) foam here in Sweden to add to the result. [also saw an experiment using the JKW plant sap mixed in to fool the plant to get the rest down. Something from Wales]

What about other foiliage or trees intertwined when spraying

Yes, an excellent video. It would be appreciated if you could acknowledge the academic work of Swansea University, who you quote. I'm Welsh, and I appreciate local academics who promote good Science, rather than their usual propaganda. I've treated, with stem injection, a 5mx5m stand of Japanese Knotweed the past 2 Septembers. Some shoots are now sprouting [April 2023]. I was planning to change tack and spray upcoming shoots with Glyphosate/Blue foam. You've explained how this would be futile. I'll wait until post-flowering and adopt a double-barelled attack, with focused spraying & more stem injection.

Incredible information. Thank you so much for putting this together.

This has been really helpful. So how do you deal with it during spring and summer? Just let it grow until fall?

Thanks for this video! It shows that knotweed is easy to get rid of as long as you know what to do. Let's hope that people and governments use these steps to get rid of the plant

Won't waiting for it to flower mean a risk of seeds spreading?

Thank you very much. I needed this!

bro, thank you!! JKW is a beast.

You have given me some hope! Thank you.

Great content!! Thank you.

i have been using your product - this will be my second year i actually had good luck with cutting new pop up shoots and putting your product on the cut stem - i would also dispose of the cut portion-the return rate was slowing down with each treatment and in less quantity. i did this before mowing to prevent an accidental spread as untreated cuts would result in more new pop up shoots .i ended the season by allowing a bit more growth before fall treatment -

I saw a man kill a knot weed patch by mowing. It was at least five seasons of mowing before I didn't see knotweed shoots popping through the grass. Knotweed, along with many invasives are good for the not so invasive honeybee. Knotweed is also a valuable medicinal.

Thanks to a builder destroying over 100 Indigenous trees Holly, Oak & various pines over 60yrs old some older by clearing 3 lots then mowing a small manageable knot weed patch leaving all cuttings now they are everywhere, even busting the asphalt at edges of properties. And tree of heaven as sprouted up providing homes for nymph lantern flies . Most frustrating part is he cant afford to build now yet his destruction has affected all of properties also all the hawks which kept rodents in check are gone because their homes were destroyed. Our gardens are all effected. Thanks for the info we have a battle ahead of us .

I have two small areas of knotweed at my house in Bradford VT. I don’t suppose you’re in Vermont? One patch is pretty close to my well head so I worry about contamination of my well water with herbicide.

Hello John, where I’m living (Netherlands) we don’t have foam glyfosaat. Could I also follow your protocol but inject the stems instead of foaming the leaves? Cheers

I’ve had very good success cutting it with a lawn mower and line trimmer. Large stand stopped growing within 2-3 years. For reference, this was on the coast of Maine.

Really great information and presentation. Questions: what type of herbicide do you use on the knotweed? Thanks so much

I have a large hillside with knotweed infestation. It’s now the end of February. How should I begin to attack this infestation?

Do certain plants grow better against possible knowledge allelopathy?

Thanks for these videos. We’ve bought a house with a large garden and it have quite a large infestation that I will take care of this year

Is this plant good for wildlife like birds and deer

One thing I would add is to watch the periphery. Kill the new, small plants at the edge before they can get established. I am in the second year of treating a stand of knotweed with glyphosate. It has had a significant effect on the central infestation, but I recently found a greater number of new stems up to 80 or 100 feet from the central stand. The young plants respond well to glyphosate. You just have to be sure you get them.

Knotweed is a very good medicinal plant. I recently got Lyme and it has helped immensely, luckily I didn't spray or kill it in my yard now I have a new found respect for something I thought was bad.

My property is bordered (fenceline) by 4 feet - 8 feet deep knotweed. I and 2 neighbours have yards that harbour it. I managed to keep it in check last year by not disturbing it. This year a neighbour cut it all down several times in spring. As with many trees, this caused suckers or runners all over my lawn. I'm sure fragments were spewed into the lawn also. Now it's taking over my lawn, foubling weekly. Pulling does not help. Neither digging or mowing. I am not for herbicides but I am going to have to this year or watch it destroy 3 properties and make its way around the neighbourhood.

I have a large area of knotweed that was knock down by heavy winter winds looks dead eill it vmcome back only random stalks coming up. Ty

I have tried adding compost on top of it and keeping it wet to drown the roots. So far no success stopping it. I'm going to try to burn it out by adding fertilizer now.

Please comment on the best strength/dilution for foliage spray. We also inject large stems with glyphosate- is the strength/ dilution recommended the same?

Knocking down the stems allows access to other invasive vines

would rock salt aid in the dehydration of the rhizomes ? surface application after roundup? its a gravel lot and we are not concerned about damaging any other vegetation?

Can you burn it?

I have knotweed. Been trying for years to eradicate it. Have been cutting off the stem in summer and pouring weed killer into the stem. Because I thought this kills off the root. If I understand the advice given here, spraying with herbicide on the leaves in the autumn means the herbicide will get transferred to the large roots below the ground more eficiently?

Fork! Did everything right except when I saw you mention the bag thing. Yup went right through the construction bags. And the ants did also! So Hells bells I have another little patch. But I would say We’ve knocked down about 50% since last autumns first go at it.👍🏻👍🏻🙏🙏🙏🙏🫣