The alien shrub that can't be stopped

BBC ^ | 6 Oct 2022 | Zaria Gorvett

[DUMBGRUNT]

Japanese knotweed evolved in one of the harshest environments on Earth – now scientists are desperately trying to find a way to destroy it.

Where it does produce seeds, Japanese knotweed is prolific. At one research site in Philadelphia, the plants were found to produce up to 150,000 seeds each year per stem – most of which were found to be viable.

This two-part system, with above-ground and below-ground body parts, means it's extremely difficult to control Japanese knotweed with chemicals. The most effective is glyphosate, which works by inhibiting an enzyme plants need to produce amino acids, and the best way to use it is counterintuitive. As many homeowners have discovered in their zeal to eradicate the weed quickly, if you use too much, you might accidentally cause the plant to spread.

The part of Japanese knotweed that's visible above ground is the crown – this is the dominant part of the plant that's actively gathering energy. But it has backup. "Surrounding those crowns are dormant buds – so they could potentially lead to new growth, but they don't because they're being suppressed by the crown," says Eastwood. So, if you flood one of these tricky weeds with herbicide, you might kill off the crown completely – and suddenly, all its satellite buds will wake up.

[DUMBGRUNT]

IIRC my wife removed some from her hedges the local Morton Arboretum recommended cutting short and CAREFULLY painting the stumps with glyphosate (Round UP).

[Celtic Conservative]

You want to get rid of it, convince hipsters it’s a delicacy.

CC

[Ann Archy]

Isn’t KUDZU from Japan also??

[rarestia]

Many rhizome-based foliage is impossible to eradicate. I’m on property where the former owner decided it would be a great idea to plant bamboo everywhere. It was not a great idea.

Bamboo is a pestilence. It chokes out grass, destroys our native oaks by smothering their crowns, and it’s almost impossible to destroy.

The only effective way to eradicate bamboo is to dig out the root ball. I have two 4’x10’ deep holes on my property where I had massive clumps of bamboo removed from near my house. I was told it could still grow back if anything was missed, and I’m reluctant to douse my land with gly considering I’m on well water.

So my hat’s off to Japanese knotweed. If you’re anything like your cousin, I pray many generations of goats get fat on your foliage.

[rarestia]

Kudzu was used as an attempt to control illegal marijuana operations. Turns out it’s REALLY hardy. There are large tracts of west Florida that are completely covered in kudzu from the roots to the crowns of some of the tallest pines. Goats are a very effective control mechanism, FWIW.

[tlozo]

The alien shrub that can't be stopped

Impossible to eradicate. Read years ago England was going to try some insect, a sap sucker that decimates it in Japan. Only good use for it is the bees love the flowers in late summer.

," explained the botanist John Wood in 1884. He was writing a gardening manual, and heaped gushing praise on a sensational, newish shrub that that even the most hapless horticulturalist would be able to handle. It was an import from the Far East, and would make a "capital" addition to the small town garden – with pleasing red shoots, handsome heart-shaped foliage, and gracefully arching stems.

In short, Wood had nothing bad to say about the plant – which incidentally, he would soon be selling. Oh and by the way, if you left it alone to grow for a few years, it would form a "charming thicket"…

This was no ordinary bush, of course – it was Japanese knotweed, and there is one glaring detail Wood had neglected to advertise. Aside from its noble, though perhaps slightly over-hyped, aesthetic qualities, it's perversely good value, because once you have it, it's (almost) permanent – it will never die, and without drastic action, future generations will be battling forests of its dense, bamboo-like stems for the coming centuries.

[sit-rep]

i have that growing at the back of my yard. been there since I moved in almost 30 years ago. I keep it from spreading by establishing the grow lines as it sprouts out of the ground with spring time lawn mowing. by mid june it starts rapid growth to a great privacy fence!! 3 ft thick and about 14’ high!

[DJ MacWoW]

We had a very large patch of it. It took 5 years and a lot of Roundup to get rid of it.

[Olog-hai]

“Scientists don’t [usually] say never,” says (Dan) Eastwood (a professor of biosciences at Swansea University in Wales), but he is willing to take a bold position and say that you never end up killing off an established clump of Japanese knotweed permanently this way — it’s literally impossible with the chemicals that are legal. “You’ve got to admire the plant, really,” he says. …

So there are some chemicals that were made illegal that can kill it?

[metmom]

We have that pestilence growing along the roads in our area, too.

Rumor has it that even if you kill the top off and keep it killed off, it takes up to 20-30 YEARS for the rhizomes to eventually die off underground.

Apparently there is an insect that loves the stuff and keeps it under control in Japan, but they are reluctant to introduce it here since it would then become yet another invasive species and who knows what other native plants it might decide to obliterate. Not that isn’t enough knotweed to keep the insects busy for a VERY long time.

[knarf]

A LOT of photos

[daniel1212]

The Polygonaceae are a family of flowering plants known informally as the knotweed family or smartweed—buckwheat family in the United States. The name is based on the genus Polygonum, and was first used by Antoine Laurent de Jussieu in 1789 in his book, Genera Plantarum.[2] The name may refer to the many swollen nodes the stems of some species have, being derived from Greek, poly meaning 'many' and gony meaning 'knee' or 'joint'. Alternatively, it may have a different derivation, meaning 'many seeds'.[3] The Polygonaceae comprise about 1200 species[4] distributed into about 48 genera.[5] - https://en.wikipedia.org/wiki/Polygonaceae

Cutting in June results in shortened regrowth (2 to 5 feet) and elimination of persistent stems from the previous season. This is a particular advantage in riparian settings, where full-size knotweed will hang over the water, making it impossible to treat without contacting the water with herbicide solution.

Use any of these glyphosate formulations to treat knotweed foliage, waiting eight weeks after cutting or a late frost to treat. The product rates differ because the glyphosate concentration differs between products. Applications of Aquaneat will require an additional surfactant (e.g., CWC 90). No additional surfactant is needed with Glyphomate 41. If you work at the early end of the operational window, you can make a touch-up application later in the season before a killing frost. - https://extension.psu.edu/japanese-knotweed

[campaignPete R-CT]

I was too busy to do my annual knotweed extermination

Easy to kill ... In September, squirt 40% glyphosate inside the stem

Look on YouTube

[daniel1212]

Polygonum plebeium or small knotweed

[Tennessee Nana]

The city of Chattanooga got goats to take care of the Kudzu on Missionary Ridge ...

They love it !!!

:)

[Wuli]

In parts of New York north of New York City, Kudzu has made green skeleton forests of the trees. It starts climbing up the tree and if not stopped it’s foilage eventually crowds out the foilage of the tree. Most of the tree dies leaving its skeleton covered in the Kudzu.

A relative has a house in Westchester county. Every year he and I keep checking for new Kudzu starting to make a climb onto the hundreds of trees on his lot. We pull them out by the roots and for as far along the root as we can. But they are so prolific in the area it is a constant battle.

[dangus]

Interesting thing about Kudzu: It’s not the dominent pest it appears to be. You can hike through kudzu territory and think it blankets every unpaved meter of an entire county... and in reality it just blankets everywhere you can see: the edges of the woodlands.

[dangus]

So what you’re saying is kudzu is not-weed.

[central_va]

I got Asian nutsedge all over. It is hard to kill like this Jap crap.

[9YearLurker]

Maybe if things get too tough we’ll appreciate it as a food source:

https://www.phillyorchards.org/2020/04/22/japanese-knotweed-edible-medicinal-invasive/