Thank you, Matu, for initiating this great discussion. I am a Permaculture neophyte who is slowly incorporating Perma concepts into my repertoire. I've been fighting quackgrass on my tiny farm in the Puget Sound area for years. Pulling it from two beds was doable but as my veggie area grew this quickly became an exercise in futility. Sheet mulching worked to keep the leaves at bay but I found that what I was really doing was providing a perfect environment for the roots to travel vast distances to previously cleared areas.
My current and very successful solution, which I've been implementing for three years, entails a moderate initial investment in time but has really payed off in the long run. It is clearly not a Permaculture process but it has allowed me to create a quarter acre area that is quackgrass-free as long as I am vigilant and pull any sneaky culprits that seeded or evaded my initial eradication process.
When I was first starting my garden eight years ago and weeding the quackgrass by hand I found that I could do a good job but within weeks it was encroaching from all sides again. Since I live on essentially two acres of quackgrass I realized controlling encroachment would be key.
Here's my strange and unorthodox method: I found a local roofer who saves 1 foot wide by at least 4 foot long metal roofing scraps for me. (I always leave some home-canned jam, etc. with him when I pick up the material.) I dig a 10" - 12" deep trench around the area I want to clear of quackgrass and place the roofing, edge down obviously, into the trench, overlapping the ends about 4" and screwing them together. I then cover the area inside with black plastic (I've since read that clear works better) and leave that in place for at least three sunny months, sometimes a full year. I know solarizing that long really wrecks the soil but I have found quackgrass roots to be amazingly, stunningly resilient - kind of the cockroach of the flora world! If it's a smallish area I avoid the plastic and do a very thorough hand weeding. As my garden area increases in size I add more roofing accordingly, reusing redundant sections but always leaving it in place around the outer perimeter. (My wife calls it "The gulag").
I consider my method to be a compromise but it allowed me to begin learning about growing food instead of always feeling like I was at war with an enemy. And now that Permaculture has come knocking at my door I feel like I have the space, both on my land and in myself, to begin that learning process. I'm also looking forward to my future attempts rid my small orchard of quackgrass by creating guilds that bring balance back to that infested area of my property, without having to resort to my slash-and-burn gulag method.
