Oh, No, Not Knotweed!

May 8, 2019 2:39 PM

It grows rapidly. It’s nearly impossible to kill. It’s terrorized England. And now it’s all over American backyards. Knotweed can grow through cracks in cement, between floorboards, and out from the joints in a stone wall. “You can see it everywhere, along the roadside, in every city,” said Jatinder Aulakh, an assistant weed scientist at the Connecticut Agricultural Experiment Station. In the landscapes it has infested, it is impossible to imagine what was there before—and harder still to foresee a future without it. “There is no insect, pest, or disease in the United States,” Aulakh said, “that can keep it in check.”

Is knotweed the new kudzu?

“Frankly, kudzu pales by comparison in its effects to Japanese knotweed,” Robert Naczi, a curator of North American botany at the New York Botanical Garden, told me. “There are plenty of invasives [where] yes, they spread, but they’ve occupied most of the habitat that they will occupy. Japanese knotweed still has a ways to go and it appears it will—unless we do something we’ve not yet discovered—be successful in dominating the state of New York.”

Perhaps this is hyperbole however.

Not everyone is as apocalyptic as Naczi. Several ecologists I spoke to argue that lawyers and contractors in the U.K. have sown paranoia over a pesky shrub. “The contractors’ marketing is highly spurious, but you have to give them credit,” says Max Wade, an engineer with the firm AECOM who has argued that knotweed is no more likely to undermine a house than a tree. (Still, you can kill a tree in a day, and you won’t have to tell the guy who buys your house that you did.) “They’ve done a great job convincing us it’s a demon plant.” Even Jones, the Knotweed_Doktor himself, decries what he calls “hysterical” media coverage, as well as a weed-control industry he thinks has taken advantage of a desperate and ill-informed clientele.

“It’s good for business if everyone’s terrified by it,” says the British biologist John Bailey, who is known to his peers as the God of Knotweed. “But nobody talks about the benefits.” Such as: Knotweed’s late-blooming flowers provide a snack for bees in the waning days of summer and produce a mild-flavored honey. Researchers in the Czech Republic have concluded that knotweed can be effectively processed into briquette biofuels because it grows so fast. Knotweed is rich in resveratrol, the family of molecules present in red wine and thought to be responsible for the health benefits associated with wine consumption. If it’s not growing in contaminated urban soil, it’s edible, with a lemony flavor and juicy crunch. Also, it’s just really interesting.

No matter your thoughts on the plant, its coming for you!

posted by Homo neanderthalensis (93 comments total)

In 1850, von Siebold shipped a bundle of knotweed plants to Kew Gardens.

Fools! Did you learn nothing from the mighty hogweed!?
posted by prize bull octorok at 2:54 PM on May 8, 2019 [10 favorites]

IDK, sublimated political anger and Schlafly is how I'm fighting the knotweed out of my backyard.
posted by fluttering hellfire at 2:55 PM on May 8, 2019 [4 favorites]

Hyperbole, at Slate?? You're kidding!!!
posted by Melismata at 2:55 PM on May 8, 2019 [5 favorites]

I have a lot of this trying to take over my yard. I had no idea what it was until today and... what I've learned is alarming. (I saw it while visiting in Turkey and immediately recognized it but didn't yet know what it was. It gets around.)

What I have learned, though, is that nasturtiums can crowd it out. So I just need to let those two plants have their battle-royale. Nasturtiums are nice.
posted by sjswitzer at 2:57 PM on May 8, 2019 [18 favorites]

The gorillas will simply freeze to death in the winter.
posted by bleep at 2:57 PM on May 8, 2019 [43 favorites]

It may have "benefits", but I still hate the stuff - I think it's kind of ugly, it takes over a yard in nothing flat, and it chokes out everything else.
posted by Greg_Ace at 2:58 PM on May 8, 2019 [3 favorites]

oh, well, except nasturtiums, apparently.
posted by Greg_Ace at 2:59 PM on May 8, 2019 [3 favorites]

The article didn't go into a lot of detail, which always frustrates me in articles like these, of how the plant acts in its native environment. Is it a pest in Japan, or easily kept at bay? If so, is it just the aphids or are there other factors?

Same for kudzu; same for hogweed; same for any invasive. Japan is not a sea of nothing but knotweed; why?

I am absolutely sure ecologists who study these plants could tell the reporters something about that, but it never seems to get asked.
posted by emjaybee at 3:03 PM on May 8, 2019 [15 favorites]

Say what you will about runaway heating of the globe due to climate change, but Venus does not have a knotweed problem.
posted by maxwelton at 3:05 PM on May 8, 2019 [14 favorites]

If it's edible and at all nutritious, I'm going to say let's not get too hasty. If it can survive in all these environments now, it has a shot at it after climate change wrecks the rest of the food crops, ne?
posted by Scattercat at 3:10 PM on May 8, 2019 [8 favorites]

My wife and I bought a pretty plant at a major UK horicultural show, the sort of place where they have guest speakers and fancy food and people in hats drinking champagne. We took it home and planted it just in front of our house, the first thing we put into the garden at our first home.

A few weeks later there was a segment on the local news about Japanese knotweed, and it wasn't until about ten minutes afterwards that the realisation dawned on us that we had in fact introduced a monster into our garden, albeit one from the Royal Three Counties Show. I spent three hours the next day sifting through soil, picking out all the tiny bits of root that break off as you remove the plant, any of them capable of turning into a plant that will bury your house in two years.
posted by pipeski at 3:10 PM on May 8, 2019 [20 favorites]

No matter your thoughts on the plant, its coming for you!

Gardens: plagued by knotweed? Eat it
Japanese Knotweed: Dreadable Edible
Japanese Knotweed Recipes
posted by the man of twists and turns at 3:16 PM on May 8, 2019 [12 favorites]

We have been fighting this stuff for 20 years at my parents house. We called it "Kudzu" before we knew what it actually was (we knew it wasn't Kudzu, but it sure grew like it). My personal favorite method involved a gardening implement we found in an antique shop. Imagine a golf club with a horizontal machete blade instead of a head. Swing that through a grove of this stuff and you are down to two inch stems in no time. Of course, it's a foot tall again by next weekend, but still. I'm convinced you can watch it grow if you are even slightly patient.
posted by Rock Steady at 3:18 PM on May 8, 2019 [13 favorites]

| A view of the author's neighbor's yard
| The author's neighbor refusing to take responsibility like an adult
| The clod of dirt the author's neighbor threw at the author after the author followed the author's neighbor around their property demanding they do something about their yard
posted by fleacircus at 3:22 PM on May 8, 2019 [4 favorites]

Now I know what it's called. I will try nasturtiums to control it.

FYI... If you need to kill off a Sego Palm, then Shrimp Plant (Justicia brandegeana). I did not do it on purpose but the Shrimp Plant was mightier.
posted by narancia at 3:27 PM on May 8, 2019 [1 favorite]

Imagine a golf club with a horizontal machete blade instead of a head.
a Grass whip!
posted by the man of twists and turns at 3:29 PM on May 8, 2019 [6 favorites]

My hometown has a city-paid inspector who goes around every year and marks every yard with suspected knotweed and organizes it to be eradicated by application of herbicide.
posted by BungaDunga at 3:30 PM on May 8, 2019 [7 favorites]

Have the people who say it's worse than kudzu ever actually interacted with kudzu in the US? At peak growth rate in the summer, it can grow over a small tree in a few days and kill it. Knotweed doesn't do that.

I've been an urban stream ecologist for 20 years and I've never seen a riparian area in a developed place that doesn't have some kind of intense invasive plant problem. In New York now, it sounds like knotweed is taking over. In Maryland, it's mostly multi-flora rose. In NC, it's privet and Microstegium. In Georgia, well, it's still privet, but it's also English ivy and bamboo. Riparian areas are very vulnerable because they are more isolated than other areas so its easier for an invasive to take hold without people noticing and because they are all connected to each other and most of these things can be waterborne or transported by birds traveling along the riparian corridor. Please, kill knotweed with severe prejudice, but recognize it's just the latest in a long string of invasive species that are pretty completely devastating to our native riparian forests.
posted by hydropsyche at 3:31 PM on May 8, 2019 [49 favorites]

In those videos where you rent a herd of goats to clear out an overgrown space, they always brag about the goats eating up all the knotweed.
posted by Bee'sWing at 3:32 PM on May 8, 2019 [17 favorites]

Here's a one minute example.
posted by Bee'sWing at 3:38 PM on May 8, 2019 [3 favorites]

meanwhile, the killer bees are still moving northward ...
posted by philip-random at 3:46 PM on May 8, 2019 [4 favorites]

Hullo, I am a plant ecologist who focuses on streambank plant communities and invasive species. The last ten years of my research have been in New York, and for the last year, in Pennsylvania. Knotweed is flipping everywhere, along with a couple dozen other invasive species (and many, many other introduced species that we just don't think of as problems for one reason or another.

Re: the edibility of knotweed, techincally yes, but you want to harvest it when the shoots are young, because the stems get really tough and fibrous when they're larger. Considering it can grow visibly in a day, you get maybe a week of harvestable time when it's emerging in the spring.

Cutting it back as a control method takes a long, long time, because they store a lot of energy in their rhizomes (underground stems), and will just keep regrowing. I've had students do growth studies with knotweed, and they easily propagate it from tiny fragments of rhizome (and also often from segments of stem).
posted by pemberkins at 3:51 PM on May 8, 2019 [51 favorites]

Japanese knotweed still has a ways to go and it appears it will—unless we do something we’ve not yet discovered—be successful in dominating the state of New York.

Maj. Heinrich Strasser: Can you image us in London?
Rick Blaine: When you get there ask me!
Capt. Louis Renault: Hmmmh! Diplomats!
Maj. Heinrich Strasser: How about New York?
Rick Blaine: Well there are certain sections of New York, Major, that I wouldn't advise you to invade.
posted by BigHeartedGuy at 3:51 PM on May 8, 2019 [2 favorites]

The thing is, itadori might not even work, and Van Driesche knows it. Trials in the U.K. have brought mixed results, in part because native anthocorids gulped down the aphid eggs.

Yeah, I have to wonder how that scheme is going to work, with our Chinese Ladybugs. You remember, the ones we brought in to control the aphids, and which not only ate all the aphids, but proceeded to eat the native ladybugs.
posted by Kirth Gerson at 3:54 PM on May 8, 2019 [4 favorites]

The only surefire way to get rid of knotweed is to bring in the tribbles. They'll make short work of it. Of course, then you'll need to call in the Klingons to take care of your tribble problem.
posted by duffell at 3:56 PM on May 8, 2019 [7 favorites]

Sigh. On a visit to Connecticut in the 1970s, my mother dug up a plant and took it home to Michigan. My father spent the next 30 years trying to eradicate it. It did not undermine the foundation of the house, or even spread more than a few yards from where it had been planted. but you just couldn't get rid of it. Perhaps this is why I am today a scientist who studies invasive species.
posted by acrasis at 3:57 PM on May 8, 2019 [41 favorites]

On the issue of how something becomes invasive when it's not a problem in its native range, there are genuinely several dozen hypotheses in invasion ecology to explain such things. As with all things in science, the real answer is probably "it's a mix of all of those, and it depends on the context".

One big one is called the enemy release hypothesis, the gist of which is that when a species is transported outside its native range, it has "escaped" its natural control mechanisms (things that eat it, diseases, etc.), which gives it a competitive edge against native species that are experiencing predators and diseases. That opens the question - why aren't native diseases/pests/herbivores affecting these introduced plants?

Well, for some introduced species, they sure do - this is where context dependence comes in. For knotweed, I see very little herbivory, except during the part of the summer when Japanese beetles are out, and they go to town on it (a big effect on individual leaves, but in my experience, no negative effect on the plant as a whole).

Another idea that's interesting here is Darwin's naturalization hypothesis (for basically any idea in my field, you can find somewhere that Darwin thought of it first). Darwin proposed in On The Origin of Species that a species introduced to a new location would be less likely to successfully establish there if there are already closely related species found in that location - on the assumption that they're similar, and therefore more likely to share pests/predators/diseases/whatever, and therefore the control mechanisms of the native relative are more likely to affect the newly introduced species.

For both of these (any many other ideas about why introduced species do or don't become invasive), there's mixed evidence - dependent on the species, the environmental context, etc etc.
posted by pemberkins at 3:58 PM on May 8, 2019 [22 favorites]

a Grass whip!

"Some folks call it a sling blade, I call it a kaiser blade."
posted by Greg_Ace at 3:58 PM on May 8, 2019 [8 favorites]

Another plant in the same genus you'll see across the UK is Russian Vine. It's the stuff that eventually covers any abandoned shed, tractor, car, etc. Kind of like autonomous camouflage.

My neighbour has it, and grows it deliberately. Somehow it manages to regularly extend itself across two feet of air and attach itself to my shed. If you grab an end and pull, you can get twenty feet of vine. It's an amazing plant, really.
posted by pipeski at 4:00 PM on May 8, 2019 [4 favorites]

pemberkins, there's also a theory (not much evidence yet) that invasives that spread as seeds (a lot of weeds came to California as seeds in the ballast of ships) came without their natural endophytes, bacteria and fungi that controlled their growth in their native habitat. Now that people can catalog microbiomes, this kind of research is beginning to happen.
posted by acrasis at 4:03 PM on May 8, 2019 [9 favorites]

I made real inroads on the giant patch of what someone said was American Bamboo. I chop it down and pull it up. I laid down cardboard and scrap plywood over it; that was the most successful. But it Keeps Coming Back. A friend recommended a 2 inch paintbrush & Roundup on the cut end after chopping it. It's everywhere.
posted by theora55 at 4:25 PM on May 8, 2019 [1 favorite]

Our PNW stadium, otherwise known as My Northwest Yard, welcomes the following challengers:

Corner A: Himalayan Blackberry, reigning champ of chez maxwelton. Impossible to eradicate!
Corner B: Scotch Broom, reigning champ of roadsides and newly cleared forest, impossible to eradicate!
Corner C: English Ivy, covering your favorite trees for decades, impossible to eradicate!
Corner D: Knotweed!
Corner E: Sallal, our stealthy native challenger!
Corner F: maxwelton, with a fucking flamethrower, maybe tactical nukes if I can find them.

Guess who is going to be eliminated first?
posted by maxwelton at 4:25 PM on May 8, 2019 [26 favorites]

I have multiflora rose, too. I recently acquired a hedge trimmer.
posted by theora55 at 4:26 PM on May 8, 2019

We have a slightly larger version called giant knotweed. I used a brush weedwhacker to take it and mugwort down this winter so we could deal with some drainage issues.

The giant knotweed is just insanely good at doing what it does. We have a patch that is three or four acres.
posted by sciencegeek at 4:30 PM on May 8, 2019

But... can ya smoke it, maaaan?
posted by Saxon Kane at 4:52 PM on May 8, 2019 [2 favorites]

I remember this stuff. Ending up requiring a backhoe and some sort of elaborate scheme involving underground plastic barriers.
posted by vogon_poet at 4:54 PM on May 8, 2019

Will goats eat it?
posted by blaneyphoto at 5:13 PM on May 8, 2019 [2 favorites]

it works quite well like rhubarb. and tinctured it's a part of herbal lyme treatments. you can also make a flute from it. it's pretty tasty actually. even raw just to chew on while going for a walk.
all my homestead, rural northeast usa friends eat and enjoy it. it also helps stop erosion.
like a lot of other "invasives", it usually takes hold when soil is disturbed. road edges where fill is brought from somewhere else. it's certainly no more invasive than us humans! a herbalist friend calls it a "follower" of the plant world. he uses this label on a lot of things other people call weeds or invasives. places where humans disturb the landscape, these plants show up. hence the "follower" label. and all these "followers" have value, a tea, tincture, food, erosion control, etc. it's the universe helping us out if you're willing to entertain that narrative of how the world works.
posted by danjo at 5:13 PM on May 8, 2019 [9 favorites]

All of these descriptions of its uses skip clearly the best one, from the Japanese wikipedia page. Very roughly translated:

"If you make some cuts at the ends of a section of stalk and soak it in water, the split stalk will spread outwards like an octopus sausage. A twig, chopstick, or the like can then be passed through the hollow stalk, and the stalk can be placed in running water, where it will spin around like a water wheel."
posted by Bugbread at 5:24 PM on May 8, 2019 [16 favorites]

A knotweed water wheel in action.
posted by Bugbread at 5:26 PM on May 8, 2019 [9 favorites]

Pulled some shoots up an hour ago. Cleared it all out last year, will probably be coming up after I'm gone. Global warming? Just eat knotweed.
posted by sammyo at 5:32 PM on May 8, 2019 [1 favorite]

Chef Bun Lai of @miyassushi used knotweed but yeah you’ve got to catch it when it is tender.

And Bee’sWing, our Parks group is taking our seasonal shipment of goats Friday to munch on invasives until September!

It all feels like spoon vs ocean but at least it’s all yummy and cute.
posted by drowsy at 5:33 PM on May 8, 2019 [5 favorites]

I’ve managed to wipe out 95% of the knotweed in our yard over the past 12 years, and there was a lot of it when we moved in. I injected a couple CC’s of roundup into the full grown stems the first year, which was time consuming but got a lot of it. You can only do that if they are full grown, just inject it with a syringe below the 2nd node from the bottom. In the following years I followed the mantra of “see it, pull it”. You can’t cut it, or it grows back, and any little piece you leave around can root. So I carefully pull the shoots straight up to get as much of the shoots as possible. I had to do it every day for the first few years, but now I can check once or twice a week in knotweed growing season. I always put everything I pull up on hot pavement to dry completely on the sun before disposing of it, to make sure I don’t spread it around.

Twelve years. And there are still a few patches that sprout every year, but I am definitely winning the battle as they are weaker every year.
posted by fimbulvetr at 5:43 PM on May 8, 2019 [24 favorites]

They are worse than oxalis and that is saying something! Still, judging from my experiment in mostly ignoring them, my conclusion is that knotweed out-competes oxalis (!!) and that nasturtium somehow out-competes knotweed. I just wait until the nasturtium dominates and pull up the rest.
posted by sjswitzer at 5:55 PM on May 8, 2019 [1 favorite]

I see these "super" plants and am somewhat optimistic that our scientists could adapt them to produce food for us in the coming environmental apocalypse.

The invasive plant we deal with in Australia is Boneseed. Each plant produces 50,000 seeds per year, dispersed by birds and insects, and they permeate the soil like ticking time bombs. Infested soil contains 10,000 to 20,000 seeds per square meter. They don't sprout all at once - that would be too easy. They form a permanent seedbank that lasts over 10 years, and only send a few out to grow each time whenever the soil is disturbed or they sense sunlight - the very act of pulling one plant out triggers more seeds to start growing. Oh and they're also fire resistant, so when a wildfire sweeps through the area, these are the first seeds to sprout. So, like you pull one plant out, 5 more start growing, and you pull those 5, and then 20 more start growing...
posted by xdvesper at 5:57 PM on May 8, 2019 [4 favorites]

I just used a regular medical style syringe with a large needle to inject the knotweed in my yard, but if you are serious about it they sell professional stem injection kits. Injection really works!
posted by fimbulvetr at 6:00 PM on May 8, 2019 [4 favorites]

NOOOOOOOO! We have this in our backyard. My husband calls it “the blight”. It’s impossible to get rid of by pulling them out... though sounds like if one is diligent over many years the blight can be DESTROYED
posted by k8bot at 6:16 PM on May 8, 2019

Not just diligent, you have to dedicate yourself to getting rid of the stuff. It has to become your new hobby, life goal, sacred quest. You must be eternally vigilant and merciless. Only then will you beat it.

And never ever mow before pulling out every last shoot, or you will just multiply it with all the little pieces.
posted by fimbulvetr at 6:23 PM on May 8, 2019 [14 favorites]

On natural enemies and biocontrol, Wikipedia has plenty of relevant info, even in English:

Following earlier studies imported Japanese knotweed psyllid insects (Aphalara itadori), whose only food source is Japanese knotweed, were released at a number of sites in Britain in a study running from 1 April 2010 to 31 March 2014. In 2012, results suggested that establishment and population growth were likely, after the insects overwintered successfully.

It’s obviously not so simple but there clearly are a variety of enemies (and plant competitors) that keep it at reasonable abundance in its native range.
posted by SaltySalticid at 6:44 PM on May 8, 2019

Japan is not a sea of nothing but knotweed; why?

Ha, sure "Japan," or the big lie. I was there, on the Shonan Coast. Complete media blackout, we weren't there to save lives, we were there to evacuate the last Americans we could. Knotweed broke through the quarantine zone around Tokyo in 2006, after that it was chaos. They said if you stood still long enough, it'd grow right through you. Wouldn't believe it if I didn't see it myself. As we were moving to exfil a young American girl came up to me, she couldn't have been more then 17. Managed to get her off the last heli on the coast. I asked her what she was doing, did she not read the media reports? She said she had to stay she had to write about her experiences to get a job writing for this new online magazine. I said are you mad, all this for a website? I asked her what she was going to do after she got back, she said use her parent's money to overpay for a shitty apartment off the L in Brooklyn. She even showed me the Game Boy she was going to conspicuously play in front of everyone. Never thought I'd see her name again.
posted by geoff. at 6:50 PM on May 8, 2019 [36 favorites]

My personal favorite method involved a gardening implement we found in an antique shop. Imagine a golf club with a horizontal machete blade instead of a head. Swing that through a grove of this stuff and you are down to two inch stems in no time.

You can see 'em using these in Cool Hand Luke, to clear the side of the road; in the book, Donn Pearce goes into detail, says they call these tools Yo-yos.
posted by Rash at 7:11 PM on May 8, 2019 [1 favorite]

Sling blades?
posted by CCBC at 7:59 PM on May 8, 2019

It only took about three or four years to get rid of my knotweed. I think I pulled and dug some of it, then repeated a spot spray of roundup as new shoots appeared. It's been gone for years now.

After more than 20 years, I'm still trying to get rid of trumpet vine. A spot spray kills the shoot, but then a few weeks later, a new one pops up, often many feet away. How can it keep sprouting when it only has leaves for maybe a few weeks before I see it?
posted by jjj606 at 8:04 PM on May 8, 2019

Japan is not a sea of nothing but knotweed; why?

They have Godzilla.
posted by Naberius at 8:09 PM on May 8, 2019 [9 favorites]

Seems like it would be quicker to mow with a scythe than hacking at it with that short thing.
posted by ctmf at 8:17 PM on May 8, 2019

Is there a permaculture angle to knotweed?
posted by b1tr0t at 3:37 PM on May 8 [+] [!]

interesting. the whole concept of 'invasive species' doesn't mesh so well with permaculture. And as an anglophone ecologist who also got a humanities degree, I think using the 'invasion' terminology was a mistake. It was naive to think that the useful concept of 'species that migrate into an area and displace others' wouldn't get co-opted by our societies' xenophobias.

But these are the species who are most like human industrialization, and thrive in industrialized landscapes. Which is now most places.

so maybe a permaculturalist could use it to break up thick slabs of concrete, use it as slow-motion, pneumatic jackhammer.
posted by eustatic at 8:27 PM on May 8, 2019 [5 favorites]

Hmm, different regions, different problems. Here in the Inland Northwest, we do have our knotweeds and knapweeds, and they are invasive and noxious. But it gets cold enough here to limit their growth in ways that other areas may not have, just like kudzu is never a problem this far north. Even after reading this article, I still believe our bioregion is more threatened by yellow star thistle. I know what I am going to be talking about with our Noxious Weed County Agent during my next slow day at the Master Gardener clinic!
posted by seasparrow at 8:34 PM on May 8, 2019 [1 favorite]

I want to see this in a cage fight with Oxalis pes-caprae.
posted by The Toad at 8:45 PM on May 8, 2019

*sighs*
At least knotweed is green.

I love Idaho, but nasty weeds are a miserable fact of life here.

Rush Skeleton Weed
Puncture Vine
Bur Buttercup aka Sand Burrs
The burning and irritating Leafy Spurge
Then there's Field Bindweed and Wild Geranium and Johnson Grass aka Witch Grass.
Innumerable burrs and thistles and damn tumbleweeds.
It's enough to make you go down to the creek and eat the Poison Hemlock.
posted by BlueHorse at 8:59 PM on May 8, 2019 [1 favorite]

it also helps stop erosion.

A number of what are now considered invasives were promoted and propagated by federal agencies for erosion control and streambank stabilization (which they indeed provide); the negative ecological effects became apparent only later.

I still believe our bioregion is more threatened by yellow star thistle

In the areas where I work, yellow star thistle is more of an upland invasive, unlike the riparian area invasives like knotweed, false indigo, or reed canary grass. I would defer to more knowledgeable people as to which species might have the most significant landscape-level effects.
posted by Dip Flash at 9:43 PM on May 8, 2019 [1 favorite]

USDA is working to crossbreed knotweed with kudzu to create a vigorous carbon sink that will offset global warming.
posted by Johnny Wallflower at 9:47 PM on May 8, 2019 [18 favorites]

GODDAMNIT JOHNNY I FELL FOR THAT
posted by Homo neanderthalensis at 9:49 PM on May 8, 2019 [20 favorites]

You are welcome.
posted by Johnny Wallflower at 10:11 PM on May 8, 2019 [4 favorites]

You've been weedrolled!!
posted by Greg_Ace at 10:59 PM on May 8, 2019 [4 favorites]

So the anti-knotweed faction sure has a strategy. This has been everywhere for me today.
posted by rhizome at 11:53 PM on May 8, 2019 [2 favorites]

That USDA link comes up from time to time, but I haven't actually really given it more than a cursory glance for years. Looking at it properly again, for maybe the first time in a decade, I'm just stunned how young the lead researcher looks! I remember when the USDA report first came out, I thought the lead researcher was such a mature adult, but he's practically a little kid!!
posted by Bugbread at 12:13 AM on May 9, 2019 [4 favorites]

MetaFilter: it's kind of ugly, it takes over a yard in nothing flat, and it chokes out everything else.
posted by GenjiandProust at 1:11 AM on May 9, 2019 [8 favorites]

A number of what are now considered invasives were promoted and propagated by federal agencies for erosion control and streambank stabilization (which they indeed provide); the negative ecological effects became apparent only later.

In the UK, Network Rail used it extensively to stabilise railway embankments which they obviously now regret!
posted by atrazine at 2:04 AM on May 9, 2019 [1 favorite]

At least it sounds like the knotweed could choke out the giant hogweed.
posted by TedW at 2:51 AM on May 9, 2019 [1 favorite]

Thanks for the post. This article Increase in Leaf Mass Per Area Benefits Plant Growth at Elevated CO2 Concentration is a bit confusing but it appears Polygonum responds 'positively' to elevated CO2 - frankly I don't see any positives in it.

I see this a lot with various weeds - some barberry (Berberis) do it, but it pops up here and there across the plant world. Warming is 'only' one of the problems we have to deal with, elevated CO2 profound f*cks up the way plants grow (nutrients, flammability, root depth, you name it).
posted by unearthed at 2:51 AM on May 9, 2019 [1 favorite]

You can kill a big patch, in my experience, if you have time. Cut it down with a scythe or machete. Maybe do that a few times. Leave the stalks where they fall. Cover the whole area in think black plastic, leave it for several years. If any come out the cracks or edges or outside the area, hit them with Roundup. Once you remove the black plastic, plant what you want there. Preferably include some alternative bee friendly plants. Any survivors appear in the area, hit with Roundup. (You could douse the whole area in the glyphosphate but that would be... bad. Black plastic is a bit better.)

Yeah you can eat it but it's kind of gross. Like slimy rubarb.
posted by thefool at 3:27 AM on May 9, 2019

The whole "all the insects are dying and our environments are filled with pesticides" thing probably isn't related to our difficulties in controlling invasive plants.
posted by aspersioncast at 4:54 AM on May 9, 2019 [3 favorites]

(Website seems to be a bit wonky, but) one of our local breweries made a beer with knotweed - Olmsted's Folly. Olmsted apparently thought knotweed was just the thing to introduce to the Back Bay Fens when he designed the park.
posted by backseatpilot at 5:49 AM on May 9, 2019 [1 favorite]

On the control method of covering cut areas with tarps or black plastic - it does help, but I've definitely seen knotweed grow through thick plastic, so you want to make sure you're maintaining it well and re-covering any areas where there's damage for the plants to grow through. It's a persistent plant. I've had collected fragments of knotweed in a black trash bag, under a table, in a dark room, for months; when we found the bag again, it had grown through the bag.

Also, just since the article had maybe not the most illustrative photos:

Japanese knotweed with a person for scale, from the Irish Examiner

The thick/fibrous stem can be seen in the first photo in this article - it's not true wood (it's a herbaceous plant), but at this size it's way too tough to be pleasant eating.

Japanese knotweed starting to regenerate from nodes on a broken stem, and generally covering the whole bank on the Delaware River (shamelessly linking my own Twitter photos here)

It's related to a bunch of other species that sometimes get the common name knotweed, but this species is a beast. It was once in the genus Polygonum along with a bunch of little things that are also sometimes called knotweeds, but a lot of species have since been split out into other groups.

Japanese knotweed is Fallopia japonica, synonymous with Polygonum cuspidatum and occasionally Reynoutria japonica. Giant knotweed is Fallopia sachalinensis or Reynoutria sachalinensis (prev. Polygonum sachalinensis); Russian vine is Fallopia baldschuanica (prev. Polygonum baldschuanicum). I tend to use the Fallopia names for all three, but all names are still in use by various research groups. Taxonomy is a real trip.

The stems look kind of like bamboo (because of the distinct nodes), but it's not related to bamboo - all of these knotweeds are in the family Polygonaceae, whereas bamboo is a grass (Poaceae).
posted by pemberkins at 6:11 AM on May 9, 2019 [11 favorites]

When we were house hunting, there was a very nice house that I was deeply suspicious*about why it was in my price range. Needed some work but mostly decorating, so I’m reading along and then boom, riiiight at the bottom of the listing, a note that the property had knotweed. *sad trombone* - it can be really difficult to get a UK mortgage lender to loan on a property with untreated (or even treated) knotweed, so I was unsurprised to see it turn up again on my alerts, knocked down further and cash only buyer.

*previous deeply suspicious listings had included absolutely no central heating. 😬
posted by halcyonday at 6:28 AM on May 9, 2019 [2 favorites]

I have this blight in my life. Also in a neighbors yard with an absentee landlord, so I'll never win the war, but I try.

I root the sprouts, and also any time I turn over any area, I comb through the dirt and extract the rhizomes. I do not compost them, I trash them. The probably should be burned.

We have had some success cutting the taller plants down to the point that you can see hollow trunk, and spraying roundup into the trunk. A poor man's injection I suppose. Of course, roundup. But I guess when it's war...

It is truly a wonder of nature - impressive in it's desire to grow and propagate. Almost as bad as humans. I think you could use it's auto-propagation model as a model for self healing networks. Of course the result would almost certainly be an AI that took over the planet.

In our city there is mandatory disclosure and removal for unused heating oil tanks on a property being sold - I am in favor of a similar thing for knot weed. It could definitely knock over your house. My house went on the market in the fall - I think I know why.
posted by pilot pirx at 6:28 AM on May 9, 2019

Please for all other living beings: NO ROUNDUP.
posted by Mesaverdian at 6:33 AM on May 9, 2019 [4 favorites]

What a fascinating article. I’d never even heard of it and got a delightful read that even featured a Poe-type story of a lab tech driven to murder and madness by the cursed plant.
posted by Ghostride The Whip at 7:36 AM on May 9, 2019

Please for all other living beings: NO ROUNDUP.

I realize that Roundup has become controversial because of recent high profile lawsuits, but it has been shown to be one of the most benign and safe of all herbicides. It has almost no toxicity to mammals, unlike other herbicides. It degrades to an inactive form upon contact with the soil in a few days and does not accumulate like other herbicides.

If you are going to use a chemical herbicide, Roundup is probably your safest choice.
posted by JackFlash at 8:30 AM on May 9, 2019 [13 favorites]

If you are near water, though, please use the formulation that is safe for aquatic life (which has a different surfactant than regular roundup).
posted by Dip Flash at 8:50 AM on May 9, 2019 [8 favorites]

NO ROUNDUP: That's why the recommendation is to inject it or paint it on a cut stem. This uses only a small amount. I'm anti-Monsanto in general, but this seems reasonable. Thanks for the info on using it near water, Dip Flash, I have held off because I am 75' from a lake.

It's a plant. It is very hardy and propagates easily, but it needs sunshine, so covering it will weaken it and make it easier to pull up and extinguish. Cutting it down regularly denies sunshine to the roots. I put the cuttings in my driveway to dry out, then trash.
posted by theora55 at 9:06 AM on May 9, 2019 [2 favorites]

The NRCS knotweed control guidelines (pdf link) have details on what to apply and at what concentration. I would suggest also checking for specific state/regional guidance just in case of differences. State extension offices, conservation districts, departments of natural resources, etc, often provide guidelines.
posted by Dip Flash at 9:25 AM on May 9, 2019 [2 favorites]

I'm anti-Monsanto in general

Monsanto is now Bayer, but in any case, the patent for Roundup expired years ago. People still use the brand name generically, sort of like Kleenex. There are lots of generic alternatives available at your local hardware store if you don't want to give your money to Monsanto. Just search for the generic name "glyphosate". They will state on the label if they are formulated for aquatic use or dry ground.
posted by JackFlash at 9:31 AM on May 9, 2019 [3 favorites]

Cows. Just sayin' Cows think knotweed is a treat food. And they have jaws that can scrunch through knotweed when it is not just a three week old four foot tall baby.

My neighbour got knotweed. This is not surprising, as most years he does two sessions of outdoor garden maintenance. His solution was to apply Round-Up copiously. The round-up killed a large tree that grew on his property, but since he lives up hill slightly from us, the dismay I felt was equally about his Round-Up running off his yard onto mine where it killed a quarter of the native or heritage species I had been cultivating carefully. His knotweed also spread into my yard, into the plot where I was attempting strawberries. The strawberries are still there and doing very badly, but I keep the knotweed in check by judicious pruning. I wait until it has grown nice tall stems with nice leaves but not gone to flower and cut it down, which means about seven times a season. The roots may survive but they are getting very short of stored nutrition and every time I cut it back it is looking more and more sickly.

Since the Round-Up did not entirely work my neighbour has gone with his next option, which is gravel spread on everywhere that used to have enough soil and sunlight to grow grass. I do not think it is the yard I would want, but so long as the gravel with weeds look is what he prefers, I am very happy with it. More applications that destroy 1/4 of my vegetables and 1/4 of my ornamental plants would make me sad.
posted by Jane the Brown at 10:07 AM on May 9, 2019 [8 favorites]

Goats will eat knotweed. There are rent-a-goat outfits doing this in public parks and such.
posted by beagle at 10:14 AM on May 9, 2019 [3 favorites]

We have this, and kudzu, and bamboo, and dandelions.

And clematis, and hogweed, and pachysandra, and shattercane, and multiflora rose.

Not sure we have any natives, but the invasives do seem to have reached some sort of agreement.

My suspicion is that a combination of "roundup ready" crops being applied disproportionately to invasives and the obvious resilience of said invasives is just going to result in super-invasives, not unlike the process by which we got all the fun antibiotic-resistant bacteria.
posted by aspersioncast at 10:44 AM on May 9, 2019

"The night the kudzu knotweed has
Your pasture, you sleep like the dead ... "

— Knot James Dickey
posted by octobersurprise at 11:18 AM on May 9, 2019

The bike trail through my city is flanked by this stuff. And if it's not covered in knotweed, it's covered in garlic mustard, lesser celandine, or greater celandine. We need to get foodies in on the edible factor of the first two. Unsustainably Wildcrafted Edible Invasives Box anyone?
posted by carrioncomfort at 1:13 PM on May 9, 2019

But... can ya smoke it, maaaan?

Nope, it's notweed
posted by etherist at 4:53 PM on May 9, 2019 [4 favorites]

It's not not knotweed...
posted by Greg_Ace at 4:57 PM on May 9, 2019

I cannot believe no one has brought up the dreaded Bermuda grass. I have no oxalis problem, no knotweed, but I will spend my last dime on trying to kill the Bermuda grass without glyphosate. I swear the underground root system may very well reach across the 4750 square miles of Los Angeles county. Arrrgh!
posted by Sophie1 at 8:12 PM on May 9, 2019 [2 favorites]

Metafilter: won’t be able to handle relentless predation for pie.
posted by diziet at 6:25 AM on May 10, 2019

While explaining knotweed to someone after reading this thread, I ran across a great site for tracking sightings of invasive species (not just plants) in North America, run out of the University of Georgia, Center for Invasive Species and Ecosystem Health. Here's the distribution map for knotweed.
posted by advil at 9:22 AM on May 11, 2019 [3 favorites]