There is a huge patch of knotweed at the edge of the parking lot at my local grocery store. I never park on that side - I have this paranoia that seed heads will get caught in my bumper and I'll end up with an infestation at home. I'm already battling bittersweet, multiflora rose, buckthorn, and poison ivy. SoI don't want to add knotweed to the list.

I've used strips of carpet out behind my pond. And I do get bittersweet tunneling under the carpet. But not too bad. I try to go out weekly with a shovel and cut the plants a ground level.

My sister had a patch of knotweed at her house years ago. She said she kept on clipping off the green shoots for years, and eventually the roots gave up the ghost.

I don't like to use herbicides, but I do use them (carefully) for invasive plants. I don't have knotweed, but perhaps if you cut and paint the stems with a concentrated brush killer, it might help. This is what I do when cutting bittersweet, buckthorn, norway maples, etc. to kill the roots and prevent them from resprouting, and it's reasonably effective.

I've been clearing woody invasive plants from this lot since 2005 - it was heavily overgrown, there were bittersweet vines that were 3 inches diameter. Have made a lot of progress but they're still growing in the way back and it is a ongoing effort because the birds keep spreading the seeds!

Sorry, no really useful advice, just sympathy.

There's some knotweed down the street from me, so I guess I'll be dealing with it eventually. Maybe it will be an interesting change from garlic mustard, which came from the same neglected woodland and which, like knotweed, has a sweet looking flower that fools people into letting it stay just a little too long.

I use sheets of old plywood which my DH is always producing (not sure where it comes from, but he's in the building trades) when I have a particularly bad patch of weeds - garlic mustard, sweet autumn clematis, or trumpet vine. A sprinkling of mulch on top and it disappears from view, and doesn't cause puddles the way a tarp does. Eventually it breaks down, at least in theory.

Ooohhhh! I feel your pain. I had a bunch of it in my back yard. It's hard to explain but my garden is on top of a stone wall, and the lower "alleyway" had a thick stand of knotweed, which made its appearance in my garden eventually, as well. I attacked it one year (I think 2007) by digging up what I could, bagging it and throwing it away. Then I laid tarps over the area and whatever escaped that summer I zapped with landscaper strength Roundup. The next year I had a few here and there and zapped it again. I subsequently didn't pay attention to it and this year it's reappeared in more places than I'd like so I'm back to spraying and digging. I think you can eradicate it; you just have to be vigilant till it's completely gone.

I like the plywood and mulch idea. May try that next spring.

First year I did spray triclopyr. Last year I did not, just plucked every shoot I came across. This fall, I may spritz again.

I have trumpet vine too. It is great for it's spot - which is covering a bit of chain link fence, but it sends up shoots everywhere else and I'm always chasing after it.

I might have made a big mistake... I actually paid for and planted a sweet autumn clematis.

Froofycat, my sympathy.

My backyard is loaded with the knotweed. They encroach from my neighbor's yard.

We kept them at bay by mowing any new ones that sprout on our lawn. However, since I have been mowing, I have done a bad job. They have now moved about 4 or 5 feet into our yard.

I spent an hour hand pulling and digging out a bunch from knee high to twice my height.

Now, what to do with them? Does anyone have a suggestion?

I'm afraid of putting them into a compost pile and starting a new colony.

There's too much to bag My town will not pick up plant material.

As for the clematis, my sister gave me one of her clematis. Now that it is growing, I believe it to be the clematis terniflora because the leaf edges are smooth and not jagged edges.

Gonna wait til flowers to know for sure. Then, pulling it out and pulling my sister's hair too.

-Tina

SAC isn't rampant in zone 5, as far as I know - my sister lives in zone 6 and it's well behaved there. On the Cape, it grows in all the untended places, along roads near homes - I didn't know that when I ordered mine from White Flower Farm! It IS a lovely plant, just needs to be watched.

Tina, you could put your clippings into a plastic bag (clear or black, but clear might heat up better) and put it in direct sun and roast the plant matter for a week or two. I did this with a bag of Garlic mustard I pulled, that was flowering and I didn't want it to go to seed. It turned into a stinky rotting mush.

Thanks, terrene.

I was thinking of chopping off the roots (rhizomes) and putting them in plastic bags.

Since I don't see buds, I figure the foliage can go in the compost.

-Tina

We think the town mower contaminated our property with Japanese knotweed. It wasn't there and then it started growing along the edge of the road. Of course, there's lots of it further down the road.

DH goes out all the time with the heavy duty brush killer purchased at the farm and feed store. It is sprayed on the leaves which transport the poison to the roots. We have an occasional stem come up so you need to pay constant attention. Down the road from us it looks like some new people were able to eradicate a thick patch of it by digging it out with a backhoe. They probably also used the weed killer. I would NEVER put it in the compost pile.

Oddly enough, the weed killer doesn't effect the ditch lilies and grass. We do like the patch of lilies that are growing. Our house sits back from the road so I don't do any gardening by the road just leave it wild.

i got my clematis at mahoney's, so I hope it's not the one that is more invasive.

I suspect the knotweed came from the last home owner who used a lawn service and they dumped clippings back there and must have dumped from another location. Or, I guess birds dropped some seeds - the stuff is all over town. I am not far from train tracks, and I find all the invasive are all along the tracks - I've wondered if it's not the trains blowing seeds and or dragging overgrown leaves, etc.

Whenever I dig, I bag it in plastic and put it out with the trash. Soon the stuff will be beautifying garbage dumps somewhere.

I've read it's really hard to get all the rhizomes and even little left over roots can start new growth.

Just another note about knotweed. I went to an invasive plant class a while back, and they said that every "knuckle" on each stem is capable of becoming a new plant. So really, ALL parts of this plant should be disposed of entirely, not just the rhizomes.

I had a large patch of it when I moved into this place. It grew to be about 8 feet high and took up a full 6x8 patch of my yard last summer. I noted where it all grew, and made my plans. I got out there first thing as soon as the snow melted this year and dug up all the roots I could get out, but it still sends up shoots here and there. As I find them, I take my shovel, and cut straight down about 3 inches away from the shoot, then wiggle (I have a straight edge square shovel about 6 inches wide, not much flex) but don't scoop the dirt out (you don't need to dig out the shoots, just the woody roots). That loosens the dirt around the shoot, then grasp the shoot at the very base (try to get it below the ground slightly if you have mulch or loose dirt) and WIGGLE it as you pull it, and you'll get the whole shoot, not just breaking it off at the ground. I've been told that if you keep pulling the shoots, after you've dug out all the woody root you can (THAT is the hard part!), you will slowly rob the plant of its strength, and it will eventually give up the fight and begone.

Do NOT attempt to put ANY part of it in the compost pile! It's NOT just the roots that start new plants, it's ANY PART OF IT, so don't drop even a tiny shoot! You must BURN all of the knotweed plant and roots, as if you put it in the trash, it will then just takeover the landfill, and spread from there. If you have the concrete block to support it, you can leave the plants to completely DRY OUT, but there cannot be any soil contact of any kind, so it is just easier to burn it all.

It's an extremely invasive species here in Vermont, it's a regestered Class B Noxious Weed, and its taking over like the kudzu did down in Tennessee. Every roadside is covered in it, it has killed out almost all of our traditional roadside flora like ferns, milkweed, grasses, wildflowers. It's all dead, it's just knotweed, everywhere. Southern Vermont is basically infested beyond all hope at this point. Here's a good webpage on eradication methods:
http://efotg.sc.egov.usda.gov/references/public/VT/JS315-knotweed.pdf

For a good note: I made the effort to talk to my neighbors about what it is and how invasive it is, and EVERY ONE OF THEM let me dig it out of their yards too. So, don't be afraid to talk to your neighbors about it, there's a good chance they will be smart enough to let you eradicate it from THEIR yards too!

Here is a link that might be useful: Vermont Agency of Agriculture: Noxious Weeds

Not everyone can burn stuff - local ordinances, etc. We can't burn anything here. Knock on wood, I don't have this yet, but it is not too far down the street from me, so it's only a matter of time. The electric company is going through the state slashing and cutting trees and leaving neighborhoods looking like war zones, because of prior damage from the last two hurricanes and October blizzards, and I've noticed that without the trees, the weeds are going gangbusters this year, including the knotweed and multiflora rose, and, I'm sure, the poison ivy lurking amongst it.

When I pull garlic mustard or bittersweet, or wild grapvine or raspberry, or multiflora rose, I put the pieces in bags and put it in the trash. I don't think I'm supposed to, but can't figure out what else to do with it. I let it die completely (kind of the stinky, rotting mush mentioned above) then put it in the trash.

Dee

I end up putting a lot of yard waste into the trash too (burning is ideal, but yeah, I'm in the city too, so it's with risk). Without a car to transport waste to the recycle center, most everything ends up in the trash. I wish there was a solution that made better sense. For the knotweed, you can also leave it out on the pavement/concrete to dry out in the sun, if you have an unused parking lot or something like that.