Knotweed

[Fernsdaddy]

Can any one tell me how to get rid of this nasty knotweed from my yard, it grows along the side and behind my garage they get over 15ft. high and grow faster than I can cut them down,I've been fighting them for the last 12 years and I'm tried of fighting I just want them gone.
Thanks for any help you can give.

 

[Beth_B]

You mean this stuff?
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7484.html

Have no clue but I suggest finding the website of your state Master Gardener program (should be easy to find online) and asking there. When I lived in Colorado I had an infestation - no other term - of Canadian thistles. I was getting nastygrams and threats of fines from the city and everything I tried to eliminate them just seemed to make it worse. The Master (or in this case Mistress) gardener was incredibly helpful and gave me a strategy that worked. The strategy did involve RoundUp or its equivalent and as I recall you do not like to use commercial preparations and nor do I but IMHO if something is invasive and non-native all bets are off. Nuke it.

 

[Fernsdaddy]

I did use Round Up last year because I was told it would kill it, Round Up was a waste of money it didn't do a thing. You might be right I'll have to Nuke it.

 

[Chuck]

Can any one tell me how to get rid of this nasty knotweed from my yard, it grows along the side and behind my garage they get over 15ft. high and grow faster than I can cut them down,I've been fighting them for the last 12 years and I'm tried of fighting I just want them gone.
Thanks for any help you can give.

I have a cousin who lived in New Jersey about 4 years ago and she had this stuff in her back yard. She tried glysophate's (Round UP) to no avail. She called me and I told her to inject 2-4D after cutting the plants down to ground level. Here in Texas 2-4D is just short of an atomic bomb. It kills everything, for quite some time. So what she did was to cut everything as short as she could and then got one of those turkey baster needle syringes. She couldn't find 2-4D so I sent her a quart. After everything was cut down she went square foot by square foot and injected every single plant and then covered her entire back yard with plastic and left it for 6 months. As of 2 years ago it had not reappeared. Anyway, she was able to sell her house and move back to God's country, Texas. Whether it will work for you??? Who knows? But if it worked once it should work again

 

[Fernsdaddy]

Chuck, I'll give it a shot and see how it works, if that doesn't do it I'm going to NUKE it, I'll go to the Garden center in the morning and see what they have.

 

[Arielphf]

I think I can answer this one.

I actually control this noxious invasive plant as part of my work and got my pesticide applicator's license just for the purpose of getting rid of this stuff. We have it ALL over the banks of the West Branch of the Susquehanna river and it chokes out a ton of very important riverside habitat.

My organization's recommendations call for cutting the tall canes as near to June first as you can, then waiting 6 weeks and hitting the resprouts with some sort of glyphosate herbicide (Roundup is the one most homeowners can buy). Apply the herbicide to the the resprouts and make sure to 'spray till wet' meaning, get all of the leaf surface glistening with the chemical. Make sure you follow the label instructions on when and how to apply. This procedure has had the best results in our trials, but don't expect to get everything the first year. You will likely have to repeat this procedure for a couple of years before you can completely eradicate this pesky weed. The Japanese knotweed has an ENORMOUS root system, once established, and you need to deplete the stored energy in that root system in order to completely kill it. And once you have gotten rid of it, keep alert for reintroductions. All it takes is one small piece of this plant (it tends to reproduce vegetatively rather than by seeds) to start the whole process over again.

The good news is, we are on the verge of developing some integrated pest management strategies to control this weed. Though there are still some tests to do, we might have a way to get some biological control on it soon. Stay tuned to your local Ag extension or Forestry office for further info.

FYI - http://www.dcnr.state.pa.us/cs/groups/public/documents/document/dcnr_010254.pdf

 

[Fernsdaddy]

Arielphf, Thank for the link, I've been cutting it down for ever or at least thats how it feel. I hope this works.

 

[Beth_B]

Interesting about the huge root system - thistle is like that too and frequent cutting makes it grow back more and more vigorously. As I recall the Roundup only worked when the plants were a bit established and when applied to the leaves. Spraying on baby plants won't work.
Sounds like a nasty weed; hope you find a way to get rid of it without resorting to a scorched earth method!

 

[CanadianLori]

This is my next door neighbour's garden. Those prickly things are now invading my area. Is this the thistle you are referring to?

 

[Beth_B]

@CanadianLori, yes! They were a solid wall along the side of my house back there when I bought it, and if left unchecked quickly grew 5' tall.
Roots grow up to 15 feet down and wide. They're horrible.
http://www.ext.colostate.edu/pubs/natres/03108.html

 

[Sheal]

Try bruising the leaves before you spray with Round Up, it is more likely to get into the plants system. It will also take more than one application to kill the weeds so be persistent and spray at regular intervals to weaken the weed.