Japanese knotweed...

[Roadking]

how do you kill it? We've tried roundup, gas (shudder...) and just about everything else, including saltin the earth around the plant...It dies off and just comes back with an attitude...
Any suggestions?
Matt

[Paquebot]

Roundup wasn't developed for that and will not work. What will work is Bonide's Weed Beater Lawn Weed Killer. That also works on bindweed which Roundup does not effectively control.

Martin

[Darren]

I had knotweed show up on the property across the creek next to the highway. I haven't seen it anywhere else close. I was worried about it getting to the creek bank. I tried Roundup at least three times mixed per instructions. I waited several days between spraying and the plant showed no effect. Roundup did nothing over a period of weeks.

As a last ditch effort, I then mixed the Roundup at about double the recommended concentration. The knotweed leaves curled up by the next day. The Roundup killed it finally. I've been looking for knotweed this year. So far nothing has reemerged. Some other weeds have grown up in that spot.

I had virtually the same experience spraying autumn olive. The higher concentration killed it too. In fact there's still a brown patch around the dead plant where the grass and some multiflora were also killed.

Roundup will kill knotweed if you ignore the instructions and up the amount mixed with the water.

[ronbre]

we had a huge area of knotweed before our house fire..the best way to remove it is to dig it out..and watch for sprouts and dig them out when you see them..was really fairly easy to remove that way..it has some pretty well concentrated roots, but once they are gone..they are gone..didn't take us but maybe a year to have all the babies gone.

we did move a small amount into a wooded area so we could hang onto it..as it is edible.

[deaconjim]

Find a market for it, then something will come along and kill your entire crop.

[rowan57]

Over here Japanese Knotweed is a notifiable weed - you have to have a qualified company come and remove it. It can break through reinforced concrete, is not adversely affected by most chemicals (the top will die off but the roots keep going), and if you leave so much as 1mm of root in the ground, it can come back.

What people do here, which can cost upwards of $7,500 depending on the size of the plot, is dig out to a depth of 6ft (I believe), dispose of the soil in accordance with the law (probably has to be incinerated), then install a copper barrier which stops the knotweed and refill with clean soil.

A while ago, I remember there being some research done on a parasite which would get rid of Knotweed but I haven't heard anything about it for a while.

[Cyngbaeld]

It makes good goat feed. It can be cut and dried and baled.

[Darren]

I've read about the law in the UK requiring the landowner to remove knotweed. As you've said, the smallest piece of root will result in the plant reappearing. At least in the UK it is understood how much damage the plant can do.

In the US most folks don't understand how bad the plant is. It crowds out all of the native species. The plant produces abundant quantities of seed. If any get into a creek or stream you'll see knotweed completely obliterate anything along the stream banks.

[SirDude]

Originally Posted by deaconjim

Find a market for it, then something will come along and kill your entire crop.

That is SO true! As soon as there's a need for something, you can't find it, or it's outlawed, etc.

[Patt]

Cool there is actually an invasive weed we don't have here! Sounds like a really bad one though.

[Darren]

No Patt, knotweed has been documented in at least two counties in Arkansas which means it's probably in others.

http://plants.usda.gov/java/county?s...5&symbol=POCU6

[Patt]

We don't have it anywhere near me personally.

[Darren]

That's good, Patt. I looked at the West Virginia distribution and found they missed three counties I know of where the stuff is in plain view on road sides. Two years ago I went to a fire works show nearby. This year I went again. This time I was amazed that knotweed had taken over the stream banks in the town. It wasn't there two years ago.

[rowan57]

Originally Posted by Darren

I've read about the law in the UK requiring the landowner to remove knotweed. As you've said, the smallest piece of root will result in the plant reappearing. At least in the UK it is understood how much damage the plant can do.

In the US most folks don't understand how bad the plant is. It crowds out all of the native species. The plant produces abundant quantities of seed. If any get into a creek or stream you'll see knotweed completely obliterate anything along the stream banks.

I lived in a house as a student, a couple of years ago. I knew the house had JKNW so I told the landlords - so what? When I got my deposit back, I got a message from the landlords saying they realised how serious it was and they would take care of it. It cost them about $15,000. But, say it spread to a neighbours garden because they didnt sort it, they could be sued for a great deal.

[secretcreek]

I see Japanese Knot Weed all along the roadways around Southern Ohio/WV. It's exploded.

[snoozy]

Goats like it...

[seedspreader]

I've got a big patch on a hill in my yard that we are battling. I'll take pictures of our battle.

[Forlane]

After reading this thread I was looking out the window at the rain and noticed, I have 4 foot tall miniature trees of this stuff growing in my backyard.

I didn't really pay much attention to it but now I'm kind of worried.

Maybe I should take some pictures for verification.

-Chris

[Paquebot]

Here's the Wikipedia entry on it:
http://en.wikipedia.org/wiki/Japanese_knotweed

Neighbor planted it as something with a bamboo name 35-40 years ago and I've been fighting it ever since.

Martin

[puddlejumper007]

thank you Paquebot, it is nice to see what it looks like.....