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Japanese Knotweed-how do I get rid of it
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Posted by Catie z3-4 PEI Can (My Page) on Fri, Nov 11, 05 at 12:42
| I have a terrible problem with this INVASIVE weed. In attemptng to kill it, you stimulate it and it sends up many more shoots to take over. The shoots are extremely tough as well as the roots. We are now going to try to cover the area this fall with carpeting to impede the sunlight and 'hopefully' with the amount of snow we receive in winter, in the spring there will be less to deal with... I hope! |
Follow-Up Postings:
RE: Japanese Knotweed-how do I get rid of it
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| It will find its way past the carpet no matter what. You'll probably need RoundUp (repeated doses for several years). |
RE: Japanese Knotweed-how do I get rid of it
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The heavy guage plastic is a good idea and the plant...often referred as Canadian Bamboo...is indeed one of the worst invasives. All you can do is dig...dig and more digging. Then use Round-Up. As the shoots may come from the roots, all you can do is keep cutting them off.
Sooner or later the roots run out of energy....sooner or later. This is an exceptional plant for ensuring a slope doesn't erode, great for hillsides near water. The problem with this, if you have a clear ground that you want something growing, then Knotweed is the answer...but if you have any nearby plants...especially honeysuckle, it will take over. Anybody have an aspirin? |
RE: Japanese Knotweed-how do I get rid of it
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Hate this plant.
We've tried digging roots out, helps, but you have got to keep at it!
My mom used a weed killer, I think 24-D on hers(not my idea+I would never do it) and it still 'popped' up after several years!
Digging and smothering has kept ours a bit under control.
I think if I had planted some native shrubs last spring, maybe it would help? Had some awesome spring ephemerals(this past spring) come up where that 'stuff' used to be!
We might try 'injecting' round-up low down near the root system next year.
NH Audubon is experimenting with something this spring on several of their properties...I'm keeping a close eye+ear out... |
RE: Japanese Knotweed-how do I get rid of it
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| We have more or less eradicated the 5' square patch we inherited from the previous owner 6yrs ago. Ours was right under a 60' tall 100 year old spruce, so digging was not an option. My advice, and what worked here - Let it grow until August until nice fat canes develop, cut them off 8" above ground, jam a stick or icepick or something 8" -10" long down the cane to break the membranes inside, and use a big syringe to fill the cane with concentrated roundup. For the next few years you should get at most small twisted and stunted 6" clumps where you had 7' tall jungle before. It is now very easy to pull anything that comes up. |
RE: Japanese Knotweed-how do I get rid of it
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| I've been actively battling it for going on four seasons. It has spread into four neighbouring yards. I have a pie shaped lot. I also have a swath in my yard that is/was 24 inches by about 40 feet. I tried chopping and digging, breaking a few shovels in the process as well as using a rented mini excavator. That seemed to invigorate the roots and they spread out to about six feet wide. I tried various not so poisonous products, granular pool chlorine after wetting the leaves, vinegar and table salt as well as boiling water. two seasons ago, I tried pulling and applying ready mix roundup. Last season, I leveled the clumps and ran over them with the mower and then sprayed the 'stumps' with FULL STRENGTH Roundup concentrate. About every three to four weeks, I re-apply the round up.I've got it about 90 percent controlled in my yard. I plan to continue this in the upcoming season and hopefully eradicate in my yard and tackle my neighbours yards as well. It was growing when I bought the place 9 years ago and like the instant privacy fence, but started to resent the bees, hornets and wasps in late summer. It seemed to hold the mosquitoes during the day as well. When I mowed the lawn, I would be attacked when I brushed aganst it. It was also a pain to remove all the dead stalks in the fall. |
RE: Japanese Knotweed-how do I get rid of it
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| A flame thrower comes to mind...lol jeff |
RE: Japanese Knotweed-how do I get rid of it
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| Hand grenade? Oh never mind. It would spread root bits far and wide to regrow, and that's what it WANTS us to do, isn't it? I can hear it pleading now, just like Brier Rabbit: 'Oh please, DON'T use the hand grenade!' |
RE: Japanese Knotweed-how do I get rid of it
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| DianeKaryl said: "This is an exceptional plant for ensuring a slope doesn't erode, great for hillsides near water." It really isn't. It's a terrible invasive pest and a small fragment of root can travel far and spread it. This occurs particularly along waterways and is a plague in many natural areas along rivers and streams. There are doubtless natives that could fulfill the same function and would not cause the same problems. |
RE: Japanese Knotweed-how do I get rid of it
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| Actually, Jeff, you're right on the money with the flame thrower! Fire is one of the few ways to get rid of this nightmare, but it's not too practical for most. This plant is a big concern. It's destroying all of SW England and is a bigger problem in the maritime provinces of Canada than in the rest of the country. My sister thinks she has finally got rid of hers. Ironically her house was previously owned by a horticulturist who planted it over 30 years ago when it was in vogue. The problem is, though, it's reached over into her neighbours yard and they are not going to do anything about it - language, cultural differences and complacency have been the obstructions, so it's all a matter of time before it comes back onto her property! Somewhere on the internet there's an amazing picture of this plant actually growing up through someone's inside wooden window sill! I was looking for it today again but can't find it. Good luck! |
Here is a link that might be useful: Fact Sheet on Japanese Knotweed
RE: Japanese Knotweed-how do I get rid of it
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| Franeli, I noticed you're a NH resident. You don't happen to live near Twin Mountain, do you? If so, you (or your spouse) may be the person I spoke with a few years ago about eradicating Japanese knotweed. As I was driving by your house, I saw you out in the yard, cutting Japanese knotweed stalks, and decided to stop to talk. I've often wondered how your eradication project has progressed. |
Here is a link that might be useful: Japanese Knotweed
RE: Japanese Knotweed-how do I get rid of it
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Wow, I'm sorry to hear you have such a problem with this weed. Check on the google search engine and you will find some interesting readup on this noxious weed. I'm having my problems as well with what's call "field horsetail" that's growing in my flower gardens so I can appreciate what you are going through.
Sandy |
RE: Japanese Knotweed-how do I get rid of it
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My husband and I have been fighting this menace since the summer of 2005 - it came with the house.
Year 1 in summer cut down canes and fill with RoundUp. Just before Fall dig out root clumps and spray RoundUp on anything that was still living. We thought that would be the end of it.
Year 2 in Spring dig up remaining large root clumps (can't get to the one growing in the old stacked stone wall...yet). During the rest of the summer weekly harvesting of new sprouts from slope and back lawn - weed spike works nicely. Dispose of in sealed plastic garbage bag. Year 3 - the snow has melted and we've started our seasonal "Knotweed Patrol" in the yard. The plant is a big problem here in the Hudson Valley region. Vigilance and persistence. |
RE: Japanese Knotweed-how do I get rid of it
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| We have a huge border of this plant around our property. While I like the screen it provides, I'm just tired of it making a mess every fall. So we're attacking it with a vengeance this year, starting now. At the moment all I am doing is clearing the debris from the last two years, but as I uncover the roots I'm going to try injecting weed killer (RoundUp or Killex) straight into the exposed rhizomes. And through the summer injecting the growing plants as well. One patch behind my shed I'm going to spray well and then cover with plastic and maybe gravel as well. Also planting replacement plants in the areas as they're cleared. It'll be an ongoing attack though I expect, as within a half mile there are acres of the stuff. |
RE: Japanese Knotweed-how do I get rid of it
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| The way I found to remove knotweed is using your weed trimmer cut it down each week from spring until mid August(the plants will be small and weak by then). Then let it grow until it flowers, at this point you can shoot it with Roundup. This will kill 99% of it. The following spring after it gets a few inches tall spray any remaining plants with Roundup. That is what we did and four years later there has been no regrowth. Best of Luck. |
RE: Japanese Knotweed-how do I get rid of it
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| Chester525 - You got it!! I've had the same experience spraying at the end of the growth season. Killed the roots over the winter. Just have a small bit left to deal with. I'll keep it cut down and hit it again this fall and that should do it. |
RE: Japanese Knotweed-how do I get rid of it
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| We inherited knotweed when we moved into our house almost two years ago. After discovering it wasn't bamboo (I'm so naive!) we began an all out onslaught on it. I read into it a little bit and found a site that notes in Clark County, Washington, they did an injection of herbicide (something like Roundup concentrate) and it was 90+% effective, so here's what I did: I got some needles and syringes and injected Roundup concentrate right below the lower nodes on the large canes. On small canes (less than a 1/2 inch in diameter) I cut and poured round up concentrate. I also cut and poured with some of the large canes too. With the really small stuff, I took some Lilly Miller Blackberry Killer and poured it into a plastic dish and painted it on the leaves. The injection worked (so far anyway) about 95%. We didn't get any new shoots from the clumps where I injected the canes the previous year. There were some random shoots here and there, but smaller. Your best attack is to inject or cut and pour and paint on killer. Whatever you do, don't pull them. Even an inch of root can start a new plant. I did pull out the big root trunks on some of them and haven't had any problems, but I noticed when I pulled a couple of those huge clumps out, there were some new buds starting. It's really an amazing plant (don't get me wrong, every time I see it by the freeway or on a slope, I have fantasies of injecting it and watching it wither and die). It is great for slopes and erosion control. I also actually looked into harvesting it for medicinal uses, but it'd be hard to compete with the Chinese market. But seriously, like people say, it is just something you have to deal with for several years. Just don't let it drive you crazy. |
RE: Japanese Knotweed-how do I get rid of it
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| I guess I like doing things the hard way, but I found that digging up every inch of the garden to about 2' helped a lot. A lot of work, but effective. I still get shoots here and there from even the smallest bits of leftover root though, but this is manageable. In another area of the garden, I simply repeatedly pulled the Knotweed and allowed other weeds to grow... Not so effective as they hide rather well among the other weeds, but the competition does weaken them. I also tried the tarp in yet another area, very effective, but you have a large ugly tarp on the ground. I will try a 30% vinegar solution and see if this helps and report my results. |
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