Agropyron repens ( Elymus pyron) , AKA cheat grass, couch/cooch grass, twitch grass, quack grass, quick grass, etc - my old nemesis! All of you who are struggling with this species have my deepest sympathy. Nothing I know of that is not a horrible toxin kills it but long term deep shade/light exclusion over a very large area ( the 8 feet or of edge will be invaded by rhizomes).
I am pasting in here my comments on this plant from March, 2013 under the
thread " Couch/cooch on site where wanting to plant a food forest - any guidance appreciated"
We call it twitch grass or quackgrass around here, but it's the same thing-- very difficult to get rid of.
At my son's end of the farm, the soil is a sandy loam. He is able to get rid of Agropyron repens in a small area such as a veggie bed with a relatively modest effort of pulling and heavy mulching.
At my end of the farm, the soil is a heavy clay loam with a bad hardpan down 1 or 2 feet- the result of generations of abusive traditional farming practices,most notably plowing. Twitch grass brings out my inner Klingon and I consider it a "worthy opponent". Apparently, A repens just loves heavy clay with a hardpan, so much so, many authors call an invasion of it an indicator of this soil type.
My battles with this species are many, but the only truly effective methods for removal that I have found all include light exclusion.
1. Heavy cardboard (or plywood, 1 inch thick layers of newspaper, etc) - 4 to 6 layers deeply overlapped. A repens can send runners out for 3 or 4 feet looking for light - they can easily sneak between gaps in cardboard placement. This cover has to stay in place for at least 1 year with no gaps appearing. I have found minimal coverage of the cardboard with mulch- just enough to keep it in place- is best because then it doesn't decompose as quickly as is more likely to last long enough.
It is best to do fairly large areas at a time - remember the very long runners that will be sent out. I have covered smaller areas of around 10 square feet for over a year only to uncover them to disclose a teeming, seething mass of very healthy A repens roots (and nothing else), which were found to be connected to happily photosynthesizing leaves 4 feet away on the edge of the mulched patch.
2. Plant tees that will cast deep shade. Slow, but effective in the long run.
3. Solid poured concrete, such as a patio - not gravel or concrete patio squares. I have seen A repens appear in the middle (over 10 feet from any edge) of a professionally built gravel parking lot in town.
Things that have not worked for me
1.Tillage - this is like trying to get rid of comfrey by tillage, the opposite happens, you propagate more of them and they laugh at you.
2.Pulling/digging up all the roots one can find, then keeping all resprouting leaves to less than 4 inches tall by pulling them out when they appear. I read this one in a book, which claimed that at less than 4 in tall, they weren't contributing to the plants' reserves, thus one could eventually weaken the plants and they would die. NOT.
3. Pouring boiling vinegar over them. Obviously I had my desperate moments.
4. Planting buckwheat thickly to smother them out. A repens is allelopathic. Even with a light cultivation to form a seed bed, hardly any buckwheat sprouted ( and I had sowed the seed so thickly the ground was barely visible and I kept it well watered) and what did sprout never grew more than 4 in tall and stayed a sickly pale colour.
I am going to continue to experiment with smother crops this spring. I have a patch of twitch grass covered up with cardboard since last fall which I will uncover in late spring and plant thickly with buckwheat. Hopefully this will give the buckwheat a bit of a headstart. The theory is that buckwheat grows so thickly that it excludes light. I will sow rye into the late maturing buckwheat and allow the rye to stay in place for a couple of years. This should also help the hardpan issue. I have had old timers warn me though that getting rid of the rye may be a problem in itself.
I think that a goat enclosure around a patch of A repens should work as well, since goats will eat everything down to bare dirt if not rotated frequently. I would like to try other livestock experiments as well ( sheep, pigs, chickens), but am not living full time on my land yet, so these will have to wait.
Interesting to note that A repens roots are nutritional and
medicinal. They are a famous famine food of times past, so maybe in the event of hard times, I will be glad I couldn't get rid of them. I have tried eating them raw and they have a mild, slightly sweet flavour - not bad,really. I have read that they can be roasted and ground for a coffee substitute, like chicory or dandelion. I plan to try this out someday.
Medicinally, a tea made from them is used to treat kidney infections and kidney stones- they have a mild diuretic action. They are also used for prostate and liver problems.
So..... maybe I should turn the problem into a solution and just consume the little darlings?
Update as of Jan 2014 -
I have struggled for 5 years to establish a food forest in a hay field infested with A repens. My progress has been steady but slow, much slower than the 2 other food forests I have established years ago. The heavy clay soil and hard pan are big contributing factors, I am sure.
My advice to urban farms/gardeners is don't waste your time mulching small sections of soil, such as spot mulching around trees - this grass can send runners out up to 10 feet! Remember,these runners can easily come from your neighbour's yard. Bamboo containment-style rhizome barriers along your property line or around the perimeter of spot mulched areas might work. A repens acts a lot like a miniature running bamboo.
My experience is that even very thick overlapping
cardboard mulch up to 4 packed solid inches thick breaks down eventually and the grass is back. Notice that I have tried deeper and deeper mulch and have observed rhizomes travelling for longer and longer distances underground.
I am concentrating more and more on growing quick, dense shade - any plant ,as long as it can shade the grass. My hope is to grow shade instead of constantly heavily re-mulching. Of course,I still use mulch for good soil health, etc.
I have densely planted a couple of 40 x 50 feet sections with hybrid poplars,Norway spruce and black locust (more for nitrogen fixing/soil building than shade) and even cedar ( Thuja occidentalis ) along with shrubs and forbes that I have observed compete fairly well with A repens in my heavy clay soil --- comfrey, rhubarb, red and black currants, dandelion, ragweed, tough species roses, Kasmir tree mallow, day lily, alfalfa, red clover, chokecherry, hazels, yarrow, and apples ( fairly large when planted out, must be over 3.5 feet tall or taller than the grass).
I hope to establish deep shade, kill the quack grass over a period of several years, then eventually cut down and/or coppice most of the shade plants and plant whatever species I want. Wishful thinking? I will report back.
Another approach I am trying on what I hope will be my future garden site is the classic organic farming method of tilling up the grass, then fall seed winter rye, which is plowed down the following June and the plot re-seeded into a thick stand of buckwheat, then as the buckwheat is dying down in that fall, over seeding winter rye again, which is plowed in the following spring - a 1.5 year process. I am not a big fan of tillage/plowing, but I am running out of ideas. There is good scientific research on this method.
I have surrounded this future garden with the above mentioned dense planting of tough shade trees as a 30 foot wide windbreak on the north and east sides, the house is on the west side and the south is still open in sun trap fashion. I may plant multiple rows of comfrey and/or rhubarb along the south side - too short to shade the garden or impede frost air drainage but hopefully a rhizome barrier.
Good luck and PLEASE post any better ideas.
Manitoulin Mary