This info for your area suggests constant mowing to weaken the rhizomes. I don't know if using a broadleaf weed killer would work since I think JK is a grass, but if you can weaken the rhizomes, maybe you can over time 'paint' glyphosate on the remaining emerging JK leaves so it will translocate to the rhizomes, and leave your lawn intact. You don't want to let it flower, but put out enough leaves for the herbicide to do it's work. Fall seems top be a good time to do this. Sorry you got someone else's headache...it's going to take time to get rid of it. HTH

Here is a link that might be useful: invasive weeds of Maine

Call everyone you know. Promise them beer and pizza. And have a work party. Now!

Also contact your regional Soil Conservation Service which is likely to help or, at the last, to advise.

For many people the terms "loam" and "topsoil" are interchangeable when they should not be. Loam is a soil type, generally about 25 percent clay, 25 percent silt, 45 percent sand, and about 5 percent organic matter while "topsoil" is whatever was scraped off the top 4 to 6 inches of someplace, sometimes with organic matter added to make it look good.
That you have Knotweed in that soil indicates the soil was simply scraped off someplace where Knotweed grows and getting rid of it is difficult. Anytime you see bits and pieces of root remove them and whenever you see even a bit of plant starting to grow remove that.

First of all absolutely DO NOT let this plant grow tall and flower and have time to send its rhizomes to the center of the earth. With new shoots use Ortho Total Kill Lawn Weed Killer. It kills knotweed and many other weeds but does not kill your lawn. I've used it for the same purpose and it really works great. It actually lists knotweed in the list of weeds it kills. Wait until new shoots grow to about 3 or so inches tall with some leaf growth and then spray. The next day you will already see the knotweeed browning and curling over in its sure death. Also, be careful Ortho Total Kill comes in two varieties one that is safe for lawns and one that isnt. Look at Home Depot for the green bottle, not the blue one, if you do not want to kill your lawn. Also I would suggest buying the 32 oz. concentrate and making your own mix. Mix a tiny bit heavier to really feel the satisfaction of knocking this plant back to Japan from where it first came. Bye bye knotweed.

Battling the same issue here. It is not in the top 3 inches though, it is in the yards and yards of new fill put in behind a retaining wall to create a side yard.

I have been injecting some of them, and using a dandelion puller on some. Should I not be pulling and just cutting? It goes down really far, so digging it out will be hopeless.

Should I just let the shoots get 3 inches tall and spray? inject? paint? with full strength Roundup Concentrate? Or should I use the weed b gone max?

petchie - sorry to hear you are in the same boat as me.

I've been holding steady for the past few weeks with my knotweed problem. I'm still pulling out root clippings that have sent out shoots, although that's become harder to do each week. Mowing and bagging is next, with the grass clippings quarantined. Whatever is left after that I'll paint with herbicide in the fall, when it's most effective.

Besides some advice in this forum, I found some good information resources. For example:
http://www.glifwc.org/invasives/Fallopia_spp/control.html
http://www.co.clark.wa.us/weed/documents/2005-crockett.pdf
http://www.uri.edu/cels/ceoc/documents/japaneseKnotweed.pdf (the references at the end of this one are particularly good, I think)

In the end, it seems like herbicide cocktails directly applied (painted or injected) have a pretty good chance of success. However, it may still be a multiple-year process.

Good luck.

-Andy

You had better get to it quick smart, that stuff grows deep and spreads like wildfire. My neighbour planted it knowing what it was, and I have been battlng it for years. I complained to the City of Waterloo, they said because the neighbour knew what it was there was nothing that they would do. I have used Knock Out sucessfully but needs several treatments, the treatments must get back to the original plant to kill it properly. Let me know how you manage the problem

Paul