Getting rid of or controlling Japanese knotweed

Prepare for a novella. I've got a bamboo problem (or I assume it's bamboo, I have pics to add). My friends and I are renting a house and finally decided to plant in the yard rather than just containers. We've got three patches where there's no grass, two with ivy spread and one with bamboo plants we thought were dead. As soon as we made this decision that dead bamboo came back with a vengeance, sprouting a couple dozen shoots up to 20' from the original, dead plant. Damn zombie plants. Anyhow, we'd still like to plant in the original bed as we assume the shoots we leave alone will still propagate later and the landlord won't know the difference. The problem being, of course, bamboo is aggressive and hard to be rid of. The shoots are all connected by this crazy, deep root system (I expected shallow roots, it's a grass after all) and the mother plant is so deep I can't get it to budge.
I've seen all sorts of long winded techniques to deal with bamboo (really just starve or control) but I was hoping someone might have insight into more immediate solutions.
If I dig up the shoots in the bed will any roots I miss just sprout again?
Will the other plants farther away just spread back into the bed?
Does bamboo grow/spread quickly enough that if I cleared the bed now would I have new shoots within the season?
Even if I clear it I'm afraid I'll end up with new shoots in a few weeks but this time with my own plants to work around. On top of that there's these layers below the surface of what look like wooden boards that look almost like they're made of chips of wood (like mulch) all compacted together. I wonder if that was for the bamboo, though now it's all rotted.

yup thats bamboo its a bugger frankly . It is one of the fastest growing things I have ever seen . I cut down a patch about forty sq yards up to 5yds high last autumn I am strill cutting down new shoots and expect to do so at least the rest of this year and onto the next . Is your patch self contained or does it come from next door ? If it comes from next door and they are not cutting it down at the same tilme then getting an animal to eat it is your best bet . Otherwise if its just that little patch I would suggest cut each shoot as soon as you see it , dont let it leaf and eventually it will exhaust itself and die . But not soon .

David

Looks a bit like Japanese Knotweed- really deep roots and a massive pain to remove. It is edible (tastes a bit like rhubarb), but not the most inspiring veg and I wouldn't eat any quantity of it! In the UK it is classed as an invasive plant, not sure about the US- there may be laws requiring it's removal.

The only way I've been able to remove it is by digging it out- I've had to dig down over a meter! Then sieve all of the soil to ensure there's nothing bigger than 1 cm left- bigger bits that that resprout. It has taken me months.

you could be correct charlie I didnt look at the leaves that closely , still a bugger though

Yes, that's Japanese Knotweed. I have been battling it for years and haven't found a way to remove it, yet. It does like sun, though, so shading or tarping it might help.

Ah, well, I don't know where it started but my neighbor has it too. Sadly, he's insane and threatened my roommates with a firearm last time we tried talking to him (dude was neglecting his dog in freezing weather, not a good person).
Based on your advice the best I can think of is cutting/digging and then maybe put something down and build a bed? I don't expect to be here next year so I don't need a permanent solution honestly.

Yep, Japanese Knotweed (I grew up knowing it as bamboo). The only way I have found to kill it is to cover it with a continuous layer of black plastic for at least five years, ten is more certain. The plastic has to extend far enough to catch the underground runners that it will send up all around its perimeter. This requires active control to beat down the new growth pushing up the plastic while it is still strong. It is important that the plastic be able to float a bit (hold it down with rocks here and there), so new shoots can bulge up the plastic, get baked by the sun, and die. If you put gravel or a relatively continuous heavy layer over it, it will be able to poke through the plastic while cool, short and strong.

Even after eradicating a patch on one side of my driveway (the other side belongs to the neighbor who had no interest in controlling it), there has been a tiny shoot that comes up for the past twenty years a few times a year (pulled up as soon as I see it) twenty feet into my field. In the last couple of years, that shoot has gotten stronger and another one has appeared 8-10 feet away.

So go ahead and dig your planting spaces, pulling out every scrap of root you find and exposing it until it dries up and dies, being aware that it will be a constant battle all summer to keep the knotweed down. I have found that it tends to develop nice loose rich soil under its canopy, and strong mature stalks grow in clumps which can often be pulled up by the roots, weakening the system. You can keep the grove weak by constant vigilance, but one year of neglect will let it come back full force.

And finally, I can't imagine a landlord who would object to your beating the stuff back, as it is so invasive it will take over the entire yard if left unchecked, crowd out all other plant life, and make the area unusable by humans.

Oh man, I don't realize it was that persistent. I'll give it a try and just make sure to have any plant I put there planted elsewhere too. Sadly, the soil beneath it isn't any good either (clay and grubs) but my options are limited. Thank you again for the advice. Hopefully I can keep it down for the season at least.

In another thread someone mentioned killing persistent weeds with old roofing rubber sheets, which are more durable than black plastic, not breaking down in the sun. It might even make sense in a situation like this to purchase rubber liner material such as a small pond liner or rubber roofing.

I bet the previous people put down sheets of oriented strand board to try to block the weeds, and it just ended up decaying.

If it's coming through from next door, you might be able to block it with sheets of metal roofing placed on edge in a trench dug down below where the roots come through, like people do with actual bamboo.

Sheets of EPDM would be stronger and more durable than 6 mil black plastic, so if you can get it cheap, go for it. I found that the plastic was durable enough and cheap for the quantity I needed, so that is what I used. A couple of years later, I tried to control a much bigger patch of knotweed along the road, and discovered that they had just changed the formulation, making it actually 4.5 mil but supposedly just as strong. It disintegrated within a few months. I expect they have long since corrected their error (it was 25 years ago).

I've read of pumpkins and squash being planted in and around the knotweed to shade it out, not sure how effective this will be

Josh Huorn wrote:I've read of pumpkins and squash being planted in and around the knotweed to shade it out, not sure how effective this will be

My knotweed grows two meters tall, and has no problem growing through a cubic-meter compost pile.. so I don't think squash would shade it!

I've been working on destroying a patch coming over from next door for almost 4 years now- a concerted attempt to dig it out on my side, to cut down all shoots on both sides, and set the chickens to harass tiny shoots- its gone from a monster of a plant to about 8 shoots so far this year... so I am slowly winning! A sustained effort is necessary!

To grow there temporarily I'd resort to just using containers, and keep chopping the shading knotweed down.

There's laws here that can force you remove knotweed if it causing a nuisance- by invading someone else's land, etc. It can cause damage to foundations and things, so people tend to want to remove it promptly when it is too close to buildings. I struggled to get a mortgage because of the knotweed over 100m from my house!

we have that stuff all over around here! 25yrs. ago there was none. now its everywhere! locals call it jungle weed! a family friend had it at his fathers old house. he battled it for a few decades then hired a landscaper that had a permit for using some heavy duty herbicide. that finally took care of it!

That is Japanese knotweed (Fallopia japonica), and assuredly neither bamboo nor even a grass. It is notoriously difficult to get rid of, because it spreads by means of rhizomes, and the slightest scrap left behind will mean it regrows.



If your neighbours have the same problem you will need to liaise with them or it will keep coming back. The alternative would be a rhizome barrier under the fence.

The RHS has advice on the stuff, and this is extreme even by their standards (although, of course, the legal situation will vary in your area): https://www.rhs.org.uk/advice/profile?PID=218

On a related note, this is one of those species that has jumped the garden fence to become aggressive and has caused real damage to entire ecosystems. It's an example of why I always advise using extreme caution when introducing a novel species to a garden.

No point going to the effort of digging it if your neighbour won't cooperate. It will just come back.

Simply snip each new stalk as it comes up. 10 seconds of work every few days while it's in sprouting mood.

You'll never kill it totally while its able to sprout next door, but the energy held in the roots your side of the fence will diminish over time.

I'd chuck it on the compost but where I am we're desperate for any biomass and this wouldn't survive without watering anyway. You might want to burn it instead unless your composting method is perfect.

For shoots among the fence, tree roots, etc., breaking them off as soon as you can reach them is good practice. If you have knotweed in the open, I have found that waiting a bit until the stalks are strong, then pulling entire root clumps, gets large amounts of the plants' strength. Done diligently over the course of a summer, I have found this to reduce a dense 7 foot tall stand to weak stragglers. It does need to be repeated annually, though. Eventually this treatment will weaken a grove to the point where smothering can be practical (the new shoots won't lift up the cover).

Nasty stuff indeed !!

I did get it stopped at one time though - here's the story of that:

I was renting an apartment and was offered a garden space by the barn - with an active knotweed infestation - bleah.

Turned out the crazy landlady loved the stuff - it was her 'privacy hedge' of choice out front.
She had seen it down the road and liked it so much that she took cuttings and planted it by the road !!
Since then it had traveled many hundreds of feet and was taking over the place.

That stuff is truly mighty - it literally penetrates and shatters things like that barn's concrete block foundation !!

I went on a crusade.
Spent a couple of days tilling that entire area, digging out, chopping out & removing the knots & runners.
(Turns out is also spreads by wind blown seeds...or even the smallest cutting - the stuff spreads like wildfire.)

Spent that entire month re-digging and yanking out sprouts of it as soon as I saw them...and eventually planted good stuff there.

Managed to keep it out for the years that I was there - it seemed to go in other directions during that time & skipped the garden.

Sadly, it came right back after I'd left & did a lot of damage to that barn.
She had to replace the foundation & I've no idea if she ever accepted that it was her 'hedge' that smashed it up.
(I got called names when I tried to explain it to the old dear so I just quit trying.)

Bottom line IMO:
It can be bested without harmful chemicals with diligence & ALOT of work.

Yes, it's edible, but there is an important use for this. It is highly effective against lyme disease.

[Japanese Knotweed] is a broad-spectrum antibacterial and has been found effective against spirochetes including Borrelia burdorferi(Lyme). It is an antiviral, immunomodulator, immunostimulant, laxative, diuretic, expectorant, antitussive and a capillary stimulant. The capillary stimulant action is of specific importance in Lyme treatment as it increases the blood flow to areas where the Lyme spirochete likes to live such as the eyes, skin, heart and joints. This then helps to carry the medicinal constituents of any treatments to those places. This makes it a great addition to any Lyme treatment formula/protocol.

http://greatcape.com/blogs/lyme-wars-fighting-lyme-disease-naturally/8374477-lyme-wars-3-japanese-knotweed-facilitates-blood-flow-to-hard-to-reach-areas-herbs-to-defeat-lyme-spirochetes
http://www.hawthornehillherbs.com/node/148
http://www.mvlymecenter.org/2013/04/27/lyme-stories-steve-cabana-how-i-got-well/

When my dog got lyme, I gave her Japanese knotweed (dried in capsules); she rapidly improved. I then brought her to a vet who put her on antibiotics. I stopped the knotweed. On the antibiotics alone she relapsed sharply, but eventually got better. Given that the subject was a dog, I think we can rule out placebo effect. If she were to get lyme again, I would give her the knotweed in a flash. If I were to get lyme, I would take the knotweed, and only resort to antibiotics if the knotweed didn't work.

I have a suggestion to offer that may work but exactly how to go about executing it may take a bit of experimentation, but it is 100% organic and absolutely killed dead an entire planting of bamboo that I made. in 1 week or less!

My bamboo is: Phyloscachys Aureo Sulcatta
Common name: Yellow groove bamboo
Bamboo Category: Running bamboo:

If this method works on Japanese Knot Weed, it will have to be because of similarities but I am under the impression that it is known to work for running bamboos.

Background:
My pond is unsheltered on the west side which is the direction of the prevailing wind. In an effort to reduce evaporation losses in the summer I wished to establish a wind break and as I have bamboo groves that I planted and am familiar with I chose to use plantings taken from those groves by digging up sprouting rhizomes and planting them in a line on the western side of the pond.

Mother nature did not cooperate that spring. There were heavy rains and the pond level came up exceptionally high. The area where I planted the bamboo was inundated for several days. and all my planting was killed. (everything else growing there survived.

Further research explained what I observed. All the bamboo became as limp as a noodle and fell ove into the water. What I was able to discover was that the hollow rhizomes are conduit for air getting to the root system and apparantly that is critical to the bamboo. If the root system is submerged the hollows fill with water and disrupt the plant and kills it. Further explanations offered this as a reason for why bamboo is excellent for planting on earthen dams. The roots hold the dam together but will not invade the water as they die on that side of the grove. However the dense growth of the bamboo shades out trees whose roots are known to make the dam leak.

This suggests a means of killing the knot weed problem that you have. The pictures make it look exactly like bamboo I have seen. If your infestation is localized, if you can maintain a state of innundation for several days by building berms around it and then keep it flooded within the berms and keep it flooded for sevreal days the result may be what you want. However if the infestation is broad you may want to find an isolated patch and try it there first.

Bamboo is hard to kill yet there are herbicides that will kill it. Supposedly it will succumb to Glyphosate (aka roundup) but many people object to using that. For bamboo there are other herbicides that are supposed to be even more effective, but that would require some additional research and that is not an "organic" solution.

Clumping bamboos do not spread by rhizomes but if you want more of clumping bamboo, a lot of labor is required to dig up existing clumps, break them up and then replant. Running bamboo of course spreads itself. Those who grow running bamboos resort to techniques Such as root barriers and rhizome pruning at the edge of the grove. This is somtimes done using a "rhizome ripper" Which is little more than a subsoil plow with a sharpened leading edge on the vertical portion that penetrates the ground. Rather than being set up as centered behind the tractor, it is on an outrigger running in the ground just outside of the track width of the tractor tires so it it can be used immediately adjacent to the grove. Once the rhizomes are cut, then mowing the sprouts will result in the severed rhizome dying. Also if the cut end of the rhizome is brought to the surface, pulling on it can rip it out of the ground, promptly putting an end to its adventure. For a small grove, just cutting with a shovel, preferably a sharp edged one, will also cut the rhizomes . One must however be aware of buried pipes and cables which may be within reach of the shovel or "rhizome ripper"

Root barriers can be effective but are not necessarily effective without some attention. occasionally the rhizome will come to the surface, go over the edge of the barrier and dig back into the ground. Where exposed to the sun it turns green which helps it hide in the grass.

Best of luck in your control measures.

Knotweed is different from true bamboo in that any fragment of root in the ground, no matter if torn up and separated from its parent, will quickly grow into a new plant. I don't know about submerging clumps underwater, but there is one patch growing vigorously in a somewhat swampy area on my place, and it can overrun riverbanks and islands which sometimes are submerged for days in floodwater.

It amuses me endlessly that this monster weed can actually be both edible and very health-promoting !!
I found many articles which have great things in them about both its weediness and how to go about eating it.

This one actually has a warning that I am very glad I found:
http://www.theotherandyhamilton.com/2013/04/22/cooking-with-japanese-knotweed/

.....only use the first shoots of the year (15-20cm or 6-9 inches) as the adult plants are not only too tough to eat but they have a sap inside them that can leave your mouth blistered.

There are even videos about eating the stuff:

A very worthy read here:
http://www.huffingtonpost.com/rebecca-louie/invasive-plant-recipe-japanese-knotweed-fruit-leather_b_7279058.html
Excerpt:

Many people eradicate Japanese knotweed with herbicides, but I don’t want to put poisons in my soil. Instead, each spring I hack away at the broomstick-thick shoots as they emerge and dig up as many of the gigantic, brain-like, mother rhizome nubs as I can before crumpling into an exhausted heap.

Another good read:
http://www.eattheweeds.com/japanese-knotweed-dreadable-edible/

It’s an invasive weed in Ohio, Vermont, West Virginia, New York, Alaska, Pennsylvania, Oregon and Washington. About the only place where they are not upset with the plant is where it’s native, southeast Asia. What do they know the rest of the world doesn’t? It is said that Japanese Knotweed out lives the gardener and the garden.

Knotweed, in the Buckwheat family, is not liked in western nations because it grows around three feet a month, sends roots down some 10 feet, grows through concrete, damaging roads, dams, buildings and just about anything made by man.

We live directly across the road from a very steep bank of a nice river that is just infested with the stuff and when I walk the dog I have noticed the red shoots.
Must be time to pick some & try them out as a food !!

Shelah Horvitz wrote:Yes, it's edible, but there is an important use for this. It is highly effective against lyme disease.

I am glad Shelah brought this up. I have had Lyme a couple of times now and have used Knotweed tincture that my wife makes as part of my treatment. Great and important medicine, very high in resveratrol. It is hard to find a source that is verified as not poisoned in my town, as the city spays it with nasty chemicals as often as it can find, (and even actively tries to mobilize the population to take part as "Duluth Invaders." The medicinal, along with the edibility and excellent bee forage it provides, are among some of its attribute. I have eaten the young shoots sauteed, I think they are tasty, a lemony/ sour flavor.

Tao Orion https://permies.com/t/55694/plants/Tao-Orion-author-War-invasive discusses the species in her recent book and looks at some other uses, such as building the base of compost piles with old canes to allow oxygenation and working with the Knotweed on riparian restoration using on-going management strategies to cut and build organic gabions to slow increased water flows, especially in light of the largely absent beavers that served a similar purpose in so much of North Americas historical waterways.

Not to discount it growth rate and ability to disperse itself (I read recently that all individuals in N. America are female clones, spreading exclusively by rhizome in the introduced areas, not sure if that is true). I have witnessed that first hand. Orion makes the crucial point of placing the "invasive" phenomenon in the wider ecological context, seeing historical disturbances that have taken place and the ones taking place right now, and understanding the organism as a part of this whole and not in isolation.

I guess point being try to make your 'problems' into solutions. Get a yield, better yet get a couple, while you manage it by cutting the growth on a regular basis, the rhizomes will eventually succumb if you are diligent and patient (and give it a few years).

If you cannot beat it, eat it.

Graze in spring, bushhog to ground in fall as mulch.

Japanese Knotweed is used as animal fodder in the Far East and here in Britain it is known that cattle, sheep, horses, donkeys and goats graze the plant. Animals prefer the young shoots as they emerge in the spring and after about June the stems become rather woody. Grazing may reduce shoot densities and height but will not eradicate it. Although grazing can help reduce the spread into uninfested areas it is not a method of control. Dead stems should be cut back in winter as these can deter grazing in the spring. Continued grazing will ensure the supply of new shoots throughout the growing season.

Grazing is therefore not an eradication tool but is helpful in suppressing the plant and reducing spread.

- See more at: http://www.devon.gov.uk/control_of_knotweed#sthash.3rDE0R6V.dpuf

Has anyone tried attacking it with a propane weed burner? I haven't. I'm just curious.

Ed Sitko wrote:Has anyone tried attacking it with a propane weed burner? I haven't. I'm just curious.

That wouldn't get rid of the rhizomes. It would weaken the plant, but so would cutting it.

One solution I have read about is cutting the stems close to the ground and then diligently pouring salt dissolved in water into each and every hollow stem. This in conjunction with black tarping the whole area.
I have fortunately not had the chance to try this!

Neil Layton wrote:

Ed Sitko wrote:Has anyone tried attacking it with a propane weed burner? I haven't. I'm just curious.

I have made a huge fire on top of it (burned it for several hours at really high temperature), it took about few weeks and it grow back . Actually looks like this plant is more affected by frost/ snow, we had a late snow and a sever frost after it started growing and all of it was killed , useless to say it grow back the following week.

I have around 1000 square meters of garden invaded by this plant, and I just started to fight it last year. What a I noticed so far:
- Mulching it under a really heavy black construction poly it's working, the plant it's coming out but will remain white and rotten in few weeks. (useless to say that when removing the poly it will grow back)
- I landscaped some part of the garden and added around 1.5 m of land mixed with compost: it managed to climb all the way up!!! 1.5 m
- In our area people are controlling it by trimming it with a grass trimmer (with wire) early in the spring before it gets woody. They say the wire will also burn it a bit. Repeating this action every few weeks for 4-5 years and it's under control, leaving the property unattended for 1-2 years and it will be back.

Wiping this out would be a major and multiple year endeavor. I suggest cutting off and covering with heavy duty black plastic and then planting in containers over this area, especially for perennials. This way you will be able to take any plants you wish with you when you move without bringing chunks of knotweed to your new situation.

Another approach would be strawbale beds (with same barrier to prevent the knotweed coming up through). They are watered to begin the decomposition process (preferably with an organic fish-kelp or urine) and then topped with about 3 inches of topsoil. I am using some for plants that can't tolerate the black walnut phytotoxins in proximity to my garden in rented location. If you get bales that are tightly tied with plastic twine (or tie them with a non-decomposing rope yourself), you don't even need any other container. Now I can grow tomatoes and peppers!

Has anyone used pigs to get rid of Japanese knotweed yet? I know they are really rough on the soil and compact the ground like crazy - taking all the air and tilth out of the soil. But if they were to be used - and were successful at getting rid of the knotweed - then couldn't a backhoe be brought in to loosen up the compacted earth and add some good organic matter and sand, etc. to help loosen it up? I would love to hear how this goes. We have a sizable patch of it at my work - easily a 100' x 100'. The biggest issue is it's close to a lightly-travelled road, and our irrigation supply pump house. We could fence it off on all sides, and install a shelter for the pigs if it turns out to be a good idea. I am looking to others to hear if it has worked first, before we attempt to jump in with both feet. Thanks!

Unfortunately this is one of the invasive species that gives planting non-natives a bad name. I took desperate action but it was either the house foundation or the plant. I just don't have the physical endurance to do the kind of digging required to get up the rhizomes. The foundation won and I will do similar again if forced to.

It's been spreading from the property across the street and they refuse to do anything about it. Right now it just about has our mailbox covered. It's now growing in the center of the circular driveway in the middle of a "jungle" there so shade doesn't kill it and neither does the cramped azaleas, blackberries, salmonberries, tulip tree, mountain ash and roses gone wild in there but sadly it's slowly killing the gigantic male holly tree.

Using pigs or goats will not get rid of it because any piece of it surviving through digestion will grow where it gets dumped. It's happened to neighbors. Composting doesn't guarantee killing it off either. The state has put out bulletins that tell us to not waste time and energy on fighting these, cut them up and bag any piece of it and throw it in the garbage which is actually a good thing as whatever grows at the landfill will help decomposition of trash.

Hi Robbie, thanks. Very interesting about the way your state is dealing with it. I have to admit I'm under the impression that pigs are some of the best digesters around; the fact they are so good at rooting out the roots of things is why they'd be a potentially good option with knotweed... and yes I have read already that goats will only eat the tops, if at all. however, goats are great for controlling many other invasive plants.

I was just at the patch at my workplace today, and discovered we're not too late to pick some for eating, so I'll be getting some of the early strawberries that are coming ripe now, and make a crisp this week with it all. and I'll freeze some too, just for fun when the season is further along with other fruits. I was pleasantly surprised at how mild the taste of the peeled stalk is. I'll definitely be on it much earlier in the season next year!

You might be able to sink something circular and long far enough into the ground to prevent rhizome spread since you are actually harvesting it. Unchecked spreading is what becomes damaging. This stuff will wipe out most of a native ecology within a few years depending on how fragile it is.

My parents garden was infested with the Japanese knotweed. I was lucky in destroying it by a stroke of luck. A wet period in winter followed by a sudden period of freezing. The meteo office warned in advance so i drilled holes in the ground and i did put extra water in the holes and on top of the soil. The combinaion knocked it of. Alas that's no solution in most cases.

Several nature reserves and in many places the banks of rivers and canals are totally infested. The maintainance companies don't clean their gear and so actually spread the stuff. In one reserve a local volunteer destroys the shoots daily to weaken the infestation. It works but he s been at it for years.

Bamboe and yucca are easy to eliminate compared to Japanese knotweed.

i dont see anyone mentioning that the traditional use of knotweed is to treat constipation.
i had a big patch and pulled a lot of it, just left it to dry where it fell. my dog started grabbing the nice "sticks" when it dried. he got a case of diarrhea that was hellacious.
i had some luck pouring a little gas on the recurring shoots and lighting them on fire.
but mostly the chickens have attacked it, and even tho there is still a source on the other side of the fence, i dont see it in my yard.

i think a weed torch would work well, just make sure you hit at the roots hard.

If you plan to keep it, you can stop the roots of the Japanese Knotwood spreading, using something like a bamboo root barrier. You read more about it here: https://www.bigplantnursery.co.uk/plant-sundries/bamboo-root-barrier_1.html .

I am currently in a living situation I don't expect to be in for many years.

Luckily I had areas free of knotweed so I started gardening there. During that first season I covered the knotweed with black plastic, spring-summer-fall-winter.

The next year I covered the area with two layers of burlap, a layer of cardboard, and then as much mulch as I could get my hands on (leaves and woodchips). Then I made small circles and added soil and planted in those.

It's working well enough, I still have to pull some shoots, but I'm lazy and have done that maybe 4 times this season. The plants I planted are doing pretty good.

I don't expect that to be a "set it and forget it" solution, but I was able to grow stuff well enough.

Dave Left wrote:Has anyone used pigs to get rid of Japanese knotweed yet?  I know they are really rough on the soil and compact the ground like crazy - taking all the air and tilth out of the soil.  But if they were to be used -  and were successful at getting rid of the knotweed - then couldn't a backhoe be brought in to loosen up the compacted earth and add some good organic matter and sand, etc. to help loosen it up?  I would love to hear how this goes.  We have a sizable patch of it at my work - easily a 100' x 100'.  The biggest issue is it's close to a lightly-travelled road, and our irrigation supply pump house.  We could fence it off on all sides, and install a shelter for the pigs if it turns out to be a good idea.  I am looking to others to hear if it has worked first, before we attempt to jump in with both feet.  Thanks!

We've been pasturing our mangalitsa pigs for four years in a two acre knotweed infestation.  They have been doing a great job weakening the knotweed and have even eradicated it in the wetter areas.  It's not their favorite forage, but they do eat it, especially when I help and knock it down.  In the fall, they start digging up the rhizomes which then reroot in the spring if I don't gather and burn them.  What was once a wasteland of only knotweed is starting to grow other plants now.  We're a long way from knotweed free, and the pigs can't patrol outside the fences.

We tried sheep and goats, but they got bloat from eating a monoculture of knotweed and died, so we're not allowing our flock in the knotweed pasture again, (they do eat down the smaller infestation in another pasture for us, but there is a balance of forage there vs the monoculture so their biome can handle it.)

Best of luck everyone!

Yep, pigs. When wwoofing, I saw a patch that I was told used to be full of knotweed until the pigs went at it. When I saw it, the pigs had been moved to another field some time previously, so any remaining knotweed rhizomes would have had time to sprout. The only plant I spotted was right next to/below the fence. Okay, pigs might not be as effective everywhere, since this was in the north of Norway, so the knotweed is probably way outside its ecological optimum. Also, being on the coast, the place was quite wet. I guess in wet spots, the rhizomes might not be able to go as deep, so the pigs might have an easier time digging them out?

Eino Kenttä wrote:Yep, pigs. When wwoofing, I saw a patch that I was told used to be full of knotweed until the pigs went at it. When I saw it, the pigs had been moved to another field some time previously, so any remaining knotweed rhizomes would have had time to sprout. The only plant I spotted was right next to/below the fence. Okay, pigs might not be as effective everywhere, since this was in the north of Norway, so the knotweed is probably way outside its ecological optimum. Also, being on the coast, the place was quite wet. I guess in wet spots, the rhizomes might not be able to go as deep, so the pigs might have an easier time digging them out?

I think the hogs just like rooting in the wet areas more because there are more invertebrates to eat.  The hogs do munch on the rhizomes they dig out, but if I don't collect them before the snow, even if I'm sure they're dead, they just reroot.  I don't winter hogs in that pasture for several reasons not related to the knotweed.  Trying to keep them out on it as early and late as I can.  I expect we'll be pretty good in another five years and hopefully I'll be able to pasture them somewhere else for the summer and try put in some tree seedlings.  Not sure what do to about under the fence, (why it's such a big pasture,) or the area between the pasture and the road/driveway.  At least the knotweed is smart enough to grow away from the live wire, (funny how plants know too.)   We've been hand pulling, but these are huge areas too.  I''ll likely expand the fenced area, but I need to figure out how to keep them in next to the road without a permanent fence install.  You can tell where we've hand pulled for four years, vs not, because it grows at half the rate, but it's too hard work and we're not being successful like the hogs.  I would estimate that they've taken out about half the rhizomes in four years.  The breed and age of the hogs seems to make a difference too.  The younger pigs are hungrier and eat more of the plants in the summer, but the adult mangalitsas are the only ones who seem to be digging out rhizomes, (with those long snouts, they're really good at it!)  I currenly have six adult hogs out there on the knotweed and six younger pigs plowing out our next sheep pastures for grass/forage seeding.  Really wish we didn't have the knotweed to deal with, but at least I never have to worry about running out of pig food.

The knotweed exists in smaller patches in a few of the pastures we rotate the sheep through and they have kept it from strengthening or expanding and I consider it "managed" in those zones for now, but they don't do big damage like the hogs do and won't kill it, (and as I've mentioned are only able to eat it in polyculture.)