Killing quackgrass organically

farfarawayMay 3, 2008

Anybody got any (organic) ideas on how to kill quackgrass? It's attempting to invade one of my flowerbeds, and already has a nice foothold in another.

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The only way to keep quackgrass from invading a flower bed is to put a barrier in its way. I have found that 10 inch Aluminum flashing, inserted into the soil vertically, works well while Janet Macunovich finds plastic carpet runner works for her. I have seen that the leaves from a Balck Walnut, shredded and laid on an area the quackgrass is growing, will stop that growth and allow Perennial Rye to grow in quite thick. Otherwise the only organic method of control is to dig the stuff out rhizomes and all.

    Bookmark   May 4, 2008 at 6:27AM
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Kimmsr, THANK YOU! These are all great ideas. Digging flashing into the soil doesn't sound like a whole lot of fun, but if it will stop this insidious stuff, I'm all for it. We currently have weed cloth in several flower beds, and the quackgrass just pushes up right through it--it's the only weed that the weed cloth doesn't suppress.

I wonder, if black walnut leaves are put on the ground, can anything else grow in its place? I know black walnut is pretty toxic...will it "poison" the soil for future growth?

    Bookmark   May 4, 2008 at 9:36AM
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Where I plunked down those Black Walnut leaves only the quack grass stopped growing, the perennial rye that had beens seeded there grow up thicker, greener, faster that in other nearby places. My only regret is only having one tree to supply leaves, right now. In years past I have composted those BW leaves and have not seen any detrimental affects to plants where that compost was used. Because the purpose of the Juglone is to suppress competing growth it would be mostly located in the roots of the plants evidenced by growth suppression for years after the tree has been removed.
Digging the flashing in is not an easy job and in my Lake Michigan beach sand is even more difficult, because the sand keeps sliding back from where I shoveled it out of. Many times I will put that flashing in when the soil is still saturated from the winter in early spring just by inserting a spade straight down and then inserting the flashing. That method, in particular, requires that the top of the flashing be rolled over so the really sharp edge does not cut.

    Bookmark   May 5, 2008 at 7:06AM
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tsugajunkie z5 SE WI

I make a separate compost pile for the Black Walnut debris I get from two neighbors' yards. I have read composting will break it down, but plants like tomatoes are so ultra sensative to it that I haven't trusted that yet. Primarily because if I composted it all in my normal heap, the debris would make up about a quarter of it's mass. I will sift the Black Walnut compost and use it to start grass seed where I overseed the lawn and broadcast it as a general amendment to the lawn. I haven't tried it specifically on quackgrass, but I will now. As for it poisoning the ground, air on its own breaks down the juglone in about a year or two.


    Bookmark   May 5, 2008 at 9:56PM
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Thanks, Kimmsr and tj. Now, if only I could find a source of black walnut leaves...

    Bookmark   May 5, 2008 at 10:24PM
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joel_bc(z6 BC)

We've got about 5000 sq ft of food gardens in two major patches. We get quack grass (a.k.a. "couch grass"), because of course we've never wanted to use an herbicide. To a lesser extent, we also battle purslane, buttercup, thistle, and bindweed. With our smaller patch (about 35x35 feet), we've annually re-dug a border "incision" (narrow trench) to stop the incoming rhizomes of the quack grass. Not so practical with the larger garden, as the mineral soil there sluffs - too sandy & incoherent to retain a border trench through the year.

I rototill these plots at least twice a year (spring and fall). The rest of the time, we hand weed, using a potato fork, or a claw, or just a small trowel and our hands. We take out many, many gallons of weeds per year.

Once, we fallowed about 1/3 of our larger garden for the year. That set the quack grass back for at least two years, maybe longer! But we did not feel we could afford to forego a large area like that each year.

Rototilling between the rows of wanted plants (veggies) does suppress the weed population, but ones like quack grass and purslane do reassert themselves. I hate to till too often... I feel like I may be killing too many earthworms and beneficial soil insects, etc. What do you think?

    Bookmark   September 10, 2010 at 3:10PM
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Roto Tilling Quack (or Couch) grass simply cuts the rhizomes in small pieces and spreads it out further so you end up with more plants growing. Any tilling of Quack Grass will do the same thing. The only method of control of Quack Grass is dig out the rhizomes.

    Bookmark   September 11, 2010 at 6:24AM
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joel_bc(z6 BC)

kimmsr- yes, thorough hand weeding of the rihizomes is effective.We've found this more satisfactory, though, in the smaller of our two gardens (1600 sq feet). Because in the larger garden (4400 sq ft), the headway one makes is very slow and thend to seem small, if you're being thorough.

So hand digging the rhizomes "is as good as it gets", eh?

Oh yes, i realize now that when I talked of our experience fallowing a third of our larger garden (in my previous post), I should have mentioned that we did this not only by refraining from planting it for a year, but also by covering it in black poly sheeting. Cutting out the light and reducing the moisture really knocked the quack grass back for two or three years after the poly came off! But I tend to doubt it did the soil much general good.

    Bookmark   September 11, 2010 at 10:15AM
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Well back in the good old days my father ran chickens over the quack for a year and then planted a garden over the chicken run the next year, moving the chickens to a new area of quack. It was funny the chickens would dig down after the rhizomes and eat them with great relish. Talk about weed and feed.
On the flower bed post Kimmsr is right on. I dug all the quack with a flat spade then drove in some of that hammer in linked plastic edging 4-5 inches deep. There was no problems with quack in there this year as the plastic barrier worked. I will try the walnut leaves next year as I have two trees on the property.


    Bookmark   September 11, 2010 at 12:49PM
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joel_bc(z6 BC)

If I had access to those black-walnut trees, I sure would gather a lot of their leaves and try that approach. The dig-it-out method is quite labor-intensive, and neverending.

    Bookmark   September 11, 2010 at 5:04PM
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Have tree so in fall when my flowers are dormant is that the time to place the leaves on. I have lots of lilies,coneflowers,sedum,coralbells,obedient plants

    Bookmark   March 11, 2012 at 3:08PM
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Gardening is quite labor intensive, although if you think that labor is never ending you probably should not be involved. Gardening is very good exercise, so it is good for you.
Anyone that tells you they have a way to garden that eliminates labor is a con artist selling magic elixars that do not exist.

    Bookmark   March 13, 2012 at 6:39AM
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There is no organic way of killing quack grass outside of removing every rhizome.

I have found rhizomes over a foot deep and very sturdy in my gardens.
They will run along barriers till they find a crossing place and move in.
(my significan other sadly thinks just pulling the tops off is OK but it does make the main rhizome more sturdy and easier to get to in time)

I generally loosen the soil in a large area and then carefully and gently pull the rhizomes out by hand.

When I get tired of playing this game I will do as I have done with thistles and dig down to major rhizomes and paint them with systemic weed killer.
Works better on thistles than quack grass but it works.

    Bookmark   March 24, 2012 at 12:08AM
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*chuckle* We play the same game. I enjoy time spent pulling weeds, but my time is limited and the weeds always grow back. It's Bermuda grass for me. A good mulch tends to bring the roots to the surface, but there are always the deep ones running along the sprinkler pipes.


    Bookmark   March 26, 2012 at 10:51PM
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My nephew (a farmer with a masters in agriculture) told me that the one other method other than methodic hand digging, is to rototill frequently during the spring when the plants are the most active. Each time they are rototilled, they try to spread (and if you till once, they certainly will) After a few times of trying to spread, they actually use up all their energy and die. I've done this with a couple of sections of garden that were totally over run and I was too tired to keep digging (though I have been the West Virginia State Quack Grass Digging Champion for four years running now . . .) It definitely works, especially if you can do it when things are dry.

I hesitated to even mention this method, because it is so bad for soil structure to repeatedly rototill. (Actually, three times, a week apart, did the trick.)

    Bookmark   March 30, 2012 at 4:55PM
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Well that explains why the quack grass I have tilled under in the garden never became a problem.
Thanks for the info.

    Bookmark   March 31, 2012 at 1:26AM
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