It grows rapidly. It's nearly impossible to kill. It's terrorized England. And now it's all over my

[Demovictory9]

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“If it’s growing close to your house, there’s a potential it could send its rhizomes and break through your foundation,” says Jatinder Aulakh, an assistant weed scientist at the Connecticut Agricultural Experiment Station.
Japanese Knotweed Solutions, Ltd.

It grows rapidly. It’s nearly impossible to kill. It’s terrorized England. And now it’s all over my American backyard.

https://slate.com/technology/2019/05/japanese-knotweed-invasive-plants.html

t’s been nearly four years since I bought hypodermic needles at a CVS, squatted in my backyard, and drew them full of glyphosate. I’d done my best to build a little garden in Brooklyn, only to see the ground begin to vanish beneath the fastest-growing plant I had ever seen. It sprouted in April with a pair of tiny, beet-red leaves between the flagstones, and poked up like asparagus through the mulch. By May the leaves were flat and green and bigger than my hands, and the stems as round as a silver dollar. My neighbor’s yard provided a preview of what was coming my way: a grove as thick as a cornfield, 10 feet high, from the windows to the lot line. I had to kill the knotweed.

I was facing twin threats. The knotweed would kill my plants within months and prevent anything else from growing. But spraying the yard with Round-Up, Monsanto’s powerful herbicide, would kill everything in days. Which is why I bought the needles. The idea, which was tested in the journal Conservation Evidence, was to inject the plant’s hollow, jointed canes with weedkiller, shooting herbicide into its roots but sparing innocent neighbors from the deadly spray.

In the moment, this felt absurd, a demented instruction from the Wile E. Coyote guide to gardening. This was before I knew that two full-time knotweed fighters had, in 2004, shot glyphosate into more than 28,000 knotweed stems along Oregon’s Sandy River. Or that in the United Kingdom, it has been a crime to plant or transport unsealed knotweed since 1990. Or that right here in New York City, more than 200 acres of parkland have been overtaken by the plant.

Anyway, it didn’t work.

Japanese knotweed has come a long way since Philipp Franz von Siebold, the doctor-in-residence for the Dutch at Nagasaki, brought it to the Utrecht plant fair in the Netherlands in the 1840s. The gold-medal shrub was prized for its “gracious flowers” and advertised as ornament, medicine, wind shelter, soil retainer, dune stabilizer, cattle feed, and insect pollinator. The stems could be dried to make matchsticks, or cut and cooked like rhubarb. It crested in the dog days of summer with tassels of tiny white buds. Oh, and it grew with “great vigor.”

I tried a few different approaches: Yanking it out stalk by stalk was a sweaty, summer-long game of whack-a-mole—a thankless full-time job. Then a friend and I spent one long night digging a 10-by-4-foot trench, lining it with black contractor bags, and refilling it with dirt. It looked like we were trying to bury something, and in a way we were: the knotweed rhizomes—the plant’s creeping rootstalks—under our feet, searching for a ray of light.

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Knotweed rises on the banks of the Bronx River in New York City, where more than 200 acres of parkland is covered by knotweed.
Henry Grabar

[Thekaspervote]

1. Powerful natural weed killer

1 gal vinegar
2 cups epsom salt
Big squirt of liquid dish soap

[KPN]

5. Hmmm .... does it work on Himalayan Blackberies

do you know? Been battling them on some steep ground in my back half acre for years. This year started digging up their roots which appears to be working, but it’s a lot of— actually too much — work. Won’t use Roundup/glyphosate. i have a hand dug 30 foot deep drinking water well just below them on the slope.

[NickB79]

10. Tried it. Does nothing to deep-rooted species

All it does is dessicate the leaves. Thistles regrow their leaves in a couple weeks. Since knotweed grows from rhizomes, they'd behave the same.

[rampartc]

2. i have been fighting cayratia japonica for 20 years now.

"bushkiller vine" as it is called. i can beat it back, but it grows back quickly.

https://www.lsuagcenter.com/profiles/lbenedict/articles/page1491497309508

kudzu is bad, but this stuff will take over the planet.

[CharleyDog]

3. I have been using this brush herbicide for a horrible patch of blackberries

they are, of course, also connected by rhizomes and have gained a powerful foothold in my garden.

This brush herbicide has completely killed all the roots wherever I have used it.

It's called Image Brush and Vine Killer concentrate.

The directions say to spray it on, or "with freshly cut stumps" I painted it on with a paintbrush to the cut. Yes, it's a bit of a pain to brush it on each stump, but I didn't want to kill my garden, and it has worked really well.

on Amazon: Image by Lilly Miller Brush & Vine Killer Concentrate 32oz
This brush and vine killer kills completely - stumps and roots won't regrow
Kills blackberries, kudzu, poison oak, poison ivy, sumac and most other woody plants

It is acidic like vinegar, perhaps it is concentrated vinegar, but it works better than vinegar (I tried that before). It doesn't harm insects, bees if you don't spray it directly on them. That was a big concern for me.

[woodsprite]

8. Ooooh! Maybe I'll give it a try on our bamboo!

There is a 60’ x 10’ (and growing) swath between our house and the neighbors. The only thing is it’s inter-twined with some huge oaks and hickory trees. Wouldn’t want it to damage their roots.

[csziggy]

13. Ingredients for Image Herbicide from Lilly Miller Brush & Vine Killer Concentrate

Triclopyr and Triethylamine
Safety Data Sheet: https://images.homedepot-static.com/catalog/pdfImages/58/582eeaa1-92e5-4612-8c45-257052dd8000.pdf

We have a minor problem with Spanish bayonets - one recommendation is to trim back the spines, drill holes in the stem and pour Roundup into the holes. We dug up a bunch of them and left them with their roots hanging in the top of a brush pile. Now that it is drying out here after a wet winter I need to see if the things are still growing on those brush piles - if so, we may have to burn the entire pile, which I hate to do.

Our brush piles provide habitat for birds and small mammals which give the foxes and hawks prey. Plus they allow trees to take hold - one brush pile spot from fifteen years ago now has a small grove of black walnuts coming up. The brush is gone, broken down into the soil, but the trees that it sheltered are now big enough to make it on their own without the horses pulling up the saplings or the mowers running them over.

[diane in sf]

4. I've got a Bermuda grass problem. Someone planted it in this neighborhood in the 30s.

Horrible stuff and nothing kills it that wouldn’t poison the whole yard.

[GoCubsGo]

17. Shade kills it.

It likes full sun. Cover it with dark plastic, and that will probably get rid of it. It might take a while, but between the lack of sun and lack of water, that should be enough to take it out. When I bought my house, it had Bermuda grass. It also has lots of big trees. As they grew up and produced more shade the Bermuda grass disappeared. It lost out to my neighbors' encroaching centipede grass, which is more shade tolerant. The only place left with Bermuda grass is a microscopic sliver of the yard that gets full sun, and in the cracks where the gutter meets the street asphalt. Even paving over it didn't kill it.

[TxDemChem]

6. I had no idea

This this is completely invasive. And I thought kudzu was the only problem to look out for

[mainer]

7. Said to be a tasty veggie -- many recipes online

I've heard it resembles asparagus.

https://www.theguardian.com/lifeandstyle/shortcuts/2018/may/30/is-japanese-knotweed-driving-you-wild-dont-curse-it-cook-it

[WePurrsevere]

9. We tried pretty much everything to eradicate but no luck yet so...

now we just work on limiting it's damage and trying to think of positive things about it like...
It's a rather attractive not unpleasant smelling jerk of a plant and bees are bonkers for the flowers. It's also edible (but with cautions like with rhubarb) and has medicinal properties that tradition Chinese medicine takes advantage of and should be researched further.

IMO if you can't beat it, control it the best you can and, when possible, figure out uses for it.

[UniteFightBack]

11. Root barrier system. nt

[spinbaby]

12. My bane is chameleon plant

The last homeowner planted it as a ground cover. Its roots travel on forever and it’s stinky.

[appal_jack]

14. The hype is so overblown.

The environment is changing: temperature and rainfall disruptions, elevated CO2, soil loss, etc. Unsurprisingly, certain "invasive" plants are taking advantage of it.

Knotweed can be controlled organically by grazing and mowing. We can also accept it in certain areas. I have some just down the road. I will use the string trimmer and mower to keep it away from my foundation. I hope to get a few sheep for the pastures eventually. Where it's too wet for sheep, the knotweed will be part of the ever-evolving ecosystem. Maybe I'll get some bees some day, and they will work the summer flowers.

-app

[ismnotwasm]

15. They're like blackberries I think

We don’t poison them— I did try it, but meh. I just dig them up every time they make an appearance. They are mostly contained in my neighbors yard.

[MissB]

16. I have a patch of this.

It was here when I moved in 16 years ago. We moved in during this month back then, and the area above my driveway had these tall stalks I couldn’t identify. Turns out it was a rather healthy patch of knotweed. I started controlling it the next spring.

It’s still here.

It runs 50’ underground so it’s crossed under the road to the other side and onto a neighboring property in a gulley they don’t do anything with. It’s also crossed on the other side of my driveway but it only pokes up in one spot. I have it in my backyard in two places but there are only 4 or 5 roots.

I keep it in check by pulling it out. This time of year, I’m pulling stalks every weekend, generally I don’t let them get higher then a foot. A small piece broken off and left on the ground will grow another piece. At some point in the early summer it stops sending up stalks and just sulks in the ground, waiting for the next spring to arrive.

In the main patch above the driveway, I’ve planted food-producing perennials like goumi berries, bush cherries, pawpaw trees, lovage and chives. The knotweed tends to not come up right near those. I also have some other perennial plants like ferns, rose, hollyhock and foxglove (arguably another invasive). All in all, I keep the knotweed at bay but I won’t try the method of injection of roundup.

[mopinko]

18. finally conquered mine. fire and chickens.

pulled most of it, and as it came back up, i poured a little gas on it and lit it. or torched it w a propane torch. mostly it worked on the first shot.
still came back, weakly, then the chickens took care of it.

nasty shit.

[Codeine]

19. Could be worse; it could be the Giant Hogweed.

Giant Hogweed is an invasive species that produces a sap that can photosensitize the skin, so much so that sunlight can cause burns and blisters.

It did inspire the best song that Genesis ever produced, so it’s not all bad I guess.

[dalton99a]

20. What about Japanese knotweed in Japan?

https://medium.com/advanced-invasives/what-about-japanese-knotweed-in-japan-db989834dc0

What about Japanese knotweed in Japan?
“Why isn’t Japanese knotweed such a problem in Japan?” This is a well considered question we hear over and over at workshops and conversations about invasive plant species in the UK. The short answer is that Japanese knotweed lacks natural predation and competition outside its native environment.

Natural checks and balances

Philipp Franz Balthalzar von Siebold was the industrious German botanist and physician who first introduced Japanese knotweed into Europe in the mid 19th century. His mistake is understandable; when von Siebold first came across knotweed on the slopes of a volcano in Nagasaki Prefecture he would not have seen the prodigious density and growth of knotweed stands, so familiar along riverbanks and urban development sites in Britain today.

In Japan, knotweed exhibits characteristics of a ruderal species, spreading by seed at high altitude habitats, and also spreading by natural dispersal of vegetative material from landslides at lower altitudes. A hint of Japanese knotweed’s resilience and invasive potential is that it grows successfully on the scree and lava fields lining the slopes of Japan’s many active volcanoes. However, in the volcanic environment knotweed plants are typically much smaller in size than in Britain due to poor soils, ‘central die back’ of the plant (similar to fairy rings common in Britain), and the repeated coverings of volcanic ash and landslides that serve to limit knotweed growth.

In its Japanese habitat, knotweed is further kept in check by a large native ecosystem of similarly vigorous giant herbs such as the grasses Miscanthus and Bamboo, and natural invertebrate pests such as the psyllid Aphalara itadori. A range of Japanese soil fungi and plant diseases also attack all parts of the knotweed plant.

As a whole, the more hostile native environment helps to suppress Japanese knotweed in Japan. In urban areas, knotweed is still a problem warranting chemical control and physical management — only not to the degree that it is in Britain.