[Shinding]

It's our first year trying to grow vegetables on our new land. Our raised beds in our poly tunnel are absolutely full of, what I think is, couch grass. We've removed all the soil, pulled out all of the grass and long roots we can and layered the beds with cardboard and ground fabric.

Now we don't know whether to add the soil back or if that'll have lots of minute roots in it and the grass will start growing all over again. We can still see lots of very fine, almost spider web like roots in the soil.

Any advice would be very appreciated.

[Fleecewife]

Couch has quite thick roots with sharp spikes at the ends.  These can push straight through a growing potato so are not held back by weed suppressing fabric or cardboard - sorry!  The roots also go quite deep and the only way, other than pouring poison all over your food growing area, is to dig the whole area, and the surrounding area too, deeply, removing every section of root.


However, if you have lots of fine hairlike roots that doesn't sound like couch, maybe more like nettles, especially if they are yellowish.  The same applies though - they have to be dug out, but nettles don't grow so deeply as couch.  They do set seed though.  Fine white roots throughout the soil could also be creeping thistle - you have a battle on your hands.


First thing to do is to make a positive identification of the weeds involved.  This is fairly difficult to do at this time of year, until they start to push up some top growth.


Then you might need to dig a whole lot deeper and wider (all three of these weeds will spread sideways), then start again with fresh soil, bought in (but carefully chosen) or sieved molehill soil with good, nettle-seed free compost.  It will be hard work, but well worth it in the long run.

[Terry T]

Creeping perennial weeds can easily grow several feet in a year so to prevent them gaining access to your tunnel from outside would require a monumentous amount of digging.
I opted for only digging over my tunnel, removing the thicker more obvious roots and not all of the finer fibrous roots. I then hoe every 7-14 days through the growing season which takes 15-20 mins for a 48 x 18 foot tunnel. I have a bed system and if any perennials have emerged persistently during the growth of a crop, I dig these out once the bed is empty - a relatively easy job, once or twice a year.

Good luck!

[Shinding]

Thanks for your replies - I'm afraid we haven't gone for the full dig FW as am hoping the rhizomes won't be able to push up if they're more than 10cm under soil (as per this guy http://tonythegardener.blogspot.co.uk/p/the-way-i-get-rid-of-couch-grass-elymus.html). He seems to think that even though the grass itself goes down deeper than 15cm the rhizomes don't - but we shall see!

We sieved the soil with quite a fine sieve and am hoping the fact that the soil hasn't been watered in an age will have killed off other weeds (!? fingers crossed) so will weed as you do TT.

We may be learning a big lesson this year:)

[Fleecewife]

I'll be interested to hear how you get on. 
The rhizomes definitely grow deeper than 10cm, especially when it's loosened by digging, and easily travel more than a metre sideways. They do tend to form a dense mat near the surface, which is perhaps what he's thinking of.
 He is right about the nutrient value of these rhizomes, which is high partly because of the very fact they go down so deeply.  Sometimes you'll see dogs digging them up and eating them for their nutritional value.  One way of killing them once you've dug them up is to drown them in a barrel of water for a long time, then the rhizomes themselves can safely go on the compost heap and the liquid is used as a feed for growing plants.  We usually burn them though and spread the ash around stone fruit trees.

[Shinding]

I'm going to have nightmares about these rhizomes!! Is there any point in digging the sides of my poly tunnel if they spread so far sideways? In respect of drowning them in water FW: how long do you need to do that for? Like the idea of using them as compost and liquid fertiliser.

[Fleecewife]

When we first put up our polytunnel 20 years ago, our intention was to lay a concrete path right around the tunnel, on the outside, to stop the couch getting in.  Although we did start the foundations for it once, health got in the way, so the concrete was never laid.  The couch from outside always gets in, but as we don't grow right up to the polythene, this area can be dug over each year.  Quite honestly I don't think you can ever be rid of couch in an organic system - it will always pop up again from somewhere; just try to stay on top of it.  We have learnt to live with a certain amount of weed growth, as long as it doesn't interfere with the cropping.  Way back when we had allotments, they were infested with couch, greater bindweed and mare's tail.  The bindweed was the only one I wanted to be rid of totally - its roots go down several feet and ours grew in from the allotment next door so getting rid of it was never going to be possible.  The mare's tail wasn't so much of a nuisance as although its roots go down deeply, the foliage is quite fine and doesn't really impact on the crops.  The couch was the beginning of the never ending battle 


For soaking the roots, do it until they are dead right through - cut some to check, no white at all - then leave them a bit longer.  Better too long than not enough.

[Shinding]

Thanks very much for all your advice FW - I'm going to put the demon couch grass to good use by turning it into a fertiliser
 

[Anke]

TBH - I would just burn the couch grass roots (and the nettle roots), you can make better liquid compost by using comfrey, nettle leaves and fresh manure (we use our own goats)...

[Fleecewife]

Yes, but when the roots are there, why not have fun and make use of them    . It's all part of building up your gardening knowledge.

[arobwk]

I love couch grass - it keeps me in gardening work!! 
As advised by others, there is no easy solution.  It will creep back in no matter how much you clean your growing area.  One thought (which I picked up elsewhere) is to keep a trench around the area of concern.  The deeper the better, without getting silly.  This will allow you to better catch new rhizomes creeping towards your beds.  Otherwise, a thick plastic barrier (dug in deep) will help.  However, keeping the soil as loose as possible (after you've turned it over and pulled out as much rhizome as possible) is half the battle - makes pulling out the maximum amount of rhizome much easier when you spot new grass blades appearing. 

[doganjo]

Bury it in raw chicken muck.    If it can kill the plants we want I'm sure it can kill the couch grass. 

[Shinding]

Next job is to try and do something with flower beds that are also full of couch grass - is it worth trying to keep the flowers or should I dig the whole thing out!?

[PK]

Without having seen the state of the beds I would be inclined to remove all the plants and decide which are worth keeping. I would take the opportunity to remove any couch grass roots from the root balls and also divide any perennials to create more plants and/or rejuvenate them. Dig over the flower bed and remove as much couch as you can as you go along. Manure and replant the bed. Inevitably odd bits of couch will re-grow and they can be removed as soon as it appears. Maintain this war of attrition over the next few seasons and you will win so long as you don't let things slip and lose control.

[Shinding]

Thanks PK - have a lot of jobs on our hands.