The way I get rid of couch grass (Elymus repens)



Sorry, there is no quick way of getting rid of couch grass. It is a bit of a bind  weeding it out but just remember it is not as difficult as trying to get rid of bindweed or mares tail.  It can be a little disheartening if, after spending quite a while digging over an allotment, couch grass regenerates and makes it look very untidy. 

Couch grass spreads by rhizome (underground stem).   This is a problem because just like bindweed Calystegia sepium and mare's tail Eqisetum arvensis small pieces of rhizome left in the soil after weeding can grow into large spreading plants.  

Various rhizomous weeds drying before
composting.
The rhizomes of couch grass should not be confused with the relatively thin and fibrous roots.  The couch rhizomes are whitish cream and at each node there is usually a ragged brown leaf scale and some weak looking thin roots.  The leaves are quite soft and make up a clump throwing up flower spikes which produce flowers of about 8mm that are pressed hard to the stem.  

While couch grass is adapted to growing underground to some extent, the rhizomes rarely go deeper than about 10 cm. 

Also Elymus repens does not like to be disturbed so this could give a clue how it can be controlled. Continuously weeding it out and cultivating the ground will eventually exhaust it and it will die away. 

Experiments, over the years, show that when couch grass rhizomes are buried about 500mm deep it rarely reappears.   However, all the rhizomes must be removed from the topsoil ( top 150mm) because here they will definitely regenerate. 

There seems to be three common camps of thought about couch grass

  1. Spray, slash and burn.
I think that using a strimmer to cut off the tops of the couch grass is probably a good way of starting but I would not do that myself.  It just adds another time consuming task unnecessarily.  It will not stop you having to dig the couch out eventually.  It will be useful if you are going to cover the ground with an opaque material such as black plastic to exclude the light .  
The problem with spraying is that you probably end up eating the spray. Particularly if you are spraying on an allotment.   No matter how carefully you wash the vegetables there is still some residue of chemicals, sprayed in the past, on their surface.  In some cases chemical sprays can be taken up by vegetables and become stored in plant cells.  If you are growing to produce chemical free vegetables then using chemicals when you first take over an allotment really defeats the purpose.
On lots of allotment sites, there are people skimming off couch grass and leaving it in great mountains. I really can’t see the point of this. All those nutrients locked up in the couch and the top couple of inches of top soil all going to waste. I use an old bread tray as a sieve.  It has a one inch square mesh and this is ideal for sieving weeds.  If I were to compost this soil, it would compact the compost and squash out all the air and water pores so I don't really want it on the weed roots.  I want the compost to be mainly waste and weeds from my or other peoples' allotment not soil.  Also sieved weeds dry out much quicker and can be added to the compost after a week or two of dry weather.  


Top soil sieved from the couch grass another allotment holder gave me.


The couch grass is often left to dry off and then burnt.
If couch is burnt, some of the nutrients locked up in the grass will be lost to the atmosphere as gaseous oxides.  The nitrogen goes up as nitrous oxide and nitrogen dioxide.  The sulphur goes up as sulphur dioxide.  Phosphorous goes up in the soot.  It is calculated that 98% of nutrients are lost when stuff is burnt on the allotment.  I would rather not lose the nutrients. If you take the weeds off the allotment and do not compost them you loose the nutrients again. 
So I compost pernicious weeds, usually after drying them. See http://tonythegardener.blogspot.co.uk/p/composting-2.html
However, I am now experimenting with composting without drying the weeds first.  It takes significantly longer to complete the compost but it is still possible.

2. Cover with black plastic and wait.

I have not used black plastic often and, although it does seem to get rid of weeds, there are always some at the edges and through holes that seem to be missed.  It would be more effective if used after double digging and a layer of shreddings put over the top of it.  The idea is to exclude the light to starve the weeds.  If any light can get to the plants they will continue to photosynthesize and grow.  Only the black plastic prevents light getting to the weeds.  Blue plastic seems to allow some light through. (It’s the same if you are forcing rhubarb. The black bins are very effective; however the blue bins are useless.)  I would not necessarily use carpets to do this job because of the chemicals used in their manufacture.  Many carpets are dosed in various chemicals to stop them from rotting or getting eaten by moths.  Having said this I am using some carpets on my new allotment.  I found some at the back of the allotment under a large overhanging Crataegus monogyna  hedge.  They had been there for many years by the looks of them, and chemicals may well have been washed out over the years.  One of the principles of permaculture is to use adversity to your advantage. 


Carpets and tarpaulins covering the soil before digging. The blue plastic was on the allotment
when I took it over and it broke up and the bits are still being removed from the top soil.
 I will eventually remove the carpets from the allotment but until I do I will use them to cover weedy areas to make them easier to dig.  While covering the soil with light excluders like black plastic is very effective in starving plants, seeds produced by weeds before the soil covering will still be in the soil and viable.  As soon as you remove the covering they will germinate and cover the area with weeds again unless you cultivate.  Covering with light excluding materials like black plastic will clear the ground of top growth and this makes digging over to remove rhizomes much easier.  The plastic may eventually kill off the couch grass rhizomes too but removing them by hand seems to be much safer.

Couch and bindweed rhizomes still growing under tarpaulin and carpet.
Having just taken on a new half allotment in 2013, I covered the ground with carpet, tarpaulin and a demolished shed.   I left the coverings on for almost a year.  The neighbouring allotment and path is covered in couch grass, mare's tail and bindweed and has not been cultivated for at least two years.  (I am relieved to say I have taken over this area of the allotment too and will be able to sieve out the top soil.)
I have just finished digging this half allotment (December 2014) and finding viable rhizomes of couch grass 2 or three metres from any green couch grass growing in the soil.

These rhizomes must have been supplied with food from the couch growing in the next allotment more than one metre away.  I find this remarkable.  However, disrupting this network of underground stems seems to discourage its reemergence.  Rather than let perennial weeds irritate me for years, I tend to make sure that I remove as many of them as I can as soon as I take over an allotment.  

Four foot trench sieving the soil

Soil is sieved with the bread tray.
Not much couch, horse tail or bindweed regenerated.





If the couch grass rhizomes were not entwined with mare's tail I would bury them in the trench, however I am not risking adding this pernicious mare's tail weed to the subsoil where it will easily survive. Rather than bury, burn or throw away the rhizomes, I am drying them carefully and will add them to a separate carefully constructed compost heap. I have fairly successfully composted these dried rhizomes for a year but the compost needs to be turned quite often and sieved before use. So, probably the best way of removing the rhizomes is...

3. Do a bit of gardening and dig the weeds out.

It is harder work but far more satisfying.  Carefully digging couch rhizomes out seems to be the only way that works with any durability. As mentioned earlier, it seems that couch does not grow below about 150mm of soil so if you can bury the grass lower than that you might get rid of it. This is what I do. I dig a deep trench 600mm - 800mm deep then skim off the couch grass turfs and bury them upside down at the bottom of it.  


It is not necessary to go this deep when burying couch but a lot more grass can be buried if you do.  In this picture logs, branches, twigs and leaves are being buried as a form of Hugelkultur. The couch turfs will be put at the bottom of the trench.   
Couch grass turfs at the bottom of the trench
This does not stop the rhizomes that you miss growing again but these are relatively easy to remove by forking over the ground. It is important to realise this and not get disheartened when it grows back.  There are few gardeners who can remove every little piece of couch grass rhizome first or even second time. If you do slice off weed turfs then some of the couch grass rhizomes will still be in the soil and they will have to be removed either with the fork or by hand weeding.  The most effective way of hand weeding is with a hand fork and this will give you a fine tilth as well.

Bread tray sieve.
Another way of removing these little rhizomes is to sieve the soil through a bread tray. This is hard work but it is brilliant at removing all but the tiniest of rhizomes.  It is best to sieve the topsoil into a wheel barrow so that the soil can be inspected and any of the smaller pieces of rhizome that have slipped through the sieve can be removed. I would not recommend that you use a garden sieve because that will take you ages unless you are only doing a very small area.  The bread tray holes are about 1 inch squares and this allows the soil to fall through relatively quickly while retaining the couch and large stones.

It might be true that Elymus repens grows further down than 150 mm. but regardless, I assert that the rhizomes do not go down more than 10 cm. This is why burying by double digging seems to be an effective way of dealing with the grass.  It seems that the rhizomes cannot push leaves up to the surface at this depth.

The nutrients locked in the grass may be buried away for a year or two but they can always be brought to the surface in following years. Even at a depth of 500mm. nutrients could be available to plants with deeper roots or with a mychorrhizal symbiosis. The nutrients have not been removed completely.  

It means double digging but I think that new allotments should be double dug as soon as you get them, to sort things out like the drainage. I double dig and put the weed turfs upside down in the bottom spit.

So, no easy, quick ways of removing couch grass when it is established.  What you need to remember is that a big proportion of the nutrients are locked up in the weeds when you take over an allotment.  If you remove or burn the weeds, you remove the allotments nutrients.  

I was recently given several redcurrant bushes from a couch grass infested allotment.  Planting these bushes would lead to an infestation of couch from rhizomes embedded in the roots.  In order to remove the couch rhizomes, I washed all the soil off the roots so that I could see and fish out all the rhizomes.  This was fairly successful and no couch grass has grown from the bushes.  The bushes survived the procedure but have not fruited.  They have now 2017 and are quite spectacularly big! Always best to wash the roots of any perennial plants that are given to you to prevent contamination by couch grass.

If you have couch infested perennial flower plants then you could take them out; wash the roots and remove the couch rhizomes.  After clearing the soil off the roots the couch grass can be removed and the perennials can be replanted into clean soil. 

17 comments:

  1. Removing cough grass can be tough. Good thing you managed it well. Thanks to these must-dos you shared.

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  2. These are not must dos. It is just the way that I do it. You copy me at your own risk.
    Tony :-)

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  3. Any advantage in upending and exposing to heavy frost? Or liming?

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  4. Hi Apicius, I am fairly sure that couch grass is a hardy frost tolerant grass that would not be noticeably effected by temperatures below 0 degrees Celsius. However, it does not seem to be very tolerant of cultivation so turning couch grass infested soil over might reduce it a little. Removing the pieces of rhizome may become more difficult if they are broken up though.
    As to liming; there is evidence that suggest that couchgrass growth is reduced as the pH decreases. Adding lime to the soil will increase the pH and the growth of couch grass.
    Sorry Apicius, digging it out seems to be the only effective way of controlling it unless you succumb to the temptation of using chemicals.

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  5. That is good technique my friend.

    light clips

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  6. Hi I have a tree I think it's a bay leaf tree and it looks like it has some kind of disease the leaf's look like they have lumps on the top side underneath they are brown in sort of little pockets I can't really explain it but I reckon it's diseased or am I wrong, please help. Thank you. Maria

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  7. Bay trees planted outside have suffered this spring because plants have produced new growth but this has been severely cut back by the cold easterly wind and frosts of late March and April. I have cut all the brown leaves off the trees. Bay will regenerate from quite severe pruning.

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  8. That bread tray/wheelbarrow tip is brilliant, thank you. I got a riddle to get stones out and it's really slow going. I got my allotment late last year and spent months digging out the couch. Great blog, thanks.

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  9. Such a good post....lots of information and ideas. My new allotment is entirely smothered in couch and cannot simply be covered as I must cultivate half in the first six months to keep it. So, I've covered one third so I can dig it easier later in time for squashes and corn, I'm copying your trench idea for peas and beans and digging and sieving (best tip ever to use a bread tray and barrow) now for spuds.
    Thank you,

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  10. I remember helping my father and brother attempt to rid a large vegetable garden of couch grass, where we dug and simply turned over the soil, upending the couch rhizomes and then burying them by double-digging. Hard work, not sure whether it worked as all the digging put me off gardening until middle-age caught up with me. As far as blue bin bags go, no they won't work - I successfully propagate cuttings in blue zip-loc bags (only because I ran out of clear bags).

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  11. I have a large (and growing) pile of couch grass tops with some roots - made, I hasten to add, before I read your blog. I presume it will be ok to use this material for a bean trench dug in autumn/winter and I guess the best place for it will be at the bottom? I'm checking because burying couch grass roots will feel very risky!

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    1. I know how you feel about burying couch grass Roger. I felt like that the first time I did it. If it is just couch and no other rhizomes like bindweed or horse tail then yes I would bury couch grass in the bean trench. I must admit my bean trenches are a little deeper than most but I would be amazed if they regenerated if they are more than a spit down. If you are unsure then dry the couch grass rhizomes out first.

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  12. Thanks for the advice posted in your blog Tonythegardner. We're trying to clear our allotment of couch and it's reassuring to see that chemical free methods do work.

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  13. Oh yes organic methods work and I would avoid using any artificial chemical including glyphosate (round up) especially where I am going to grow things that I am going to eat.

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  14. A right angled, long handled fork-hoe is real labour saver when tackling couch grass. I cleared about a quarter of an acre by covering in autumn and then using the fork to rip out long lengths of weakened rhizome in the spring. The removed material was set aside to dry, then shaken and hot composted in a massive heap, using my neighbour's grass clippings to get up to 60C quickly.

    I found the bread tray tip really useful for the remainder of the job... I sieved through the top 10cm and then waited for regeneration, rather than try to pick out fragments at the point of sieving.

    The whole area was mulched with the rough compost produced from the removed mass of couch at the end of the year. I have a largely couch-free plot this spring, awaiting a double-dig.

    Thanks for the tips!

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  15. Interesting and valuable information which have share here well done.



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