Couch grass problem

[bluemobi]

We have rather a large couch grass issue all around our yard. I was wondering if anyone has any suggestions on eradicating it?

We have vacate land around us which is full of couch grass runners, so the runners keep coming up under the fence and into our garden beds. We have tried roundup on our own side of the fence and also on the other side, but it still keeps returning.

Do I need to dig a verticle trench at the fence line. How deep would it need to be? And what would I line or fill the trench with? I read somewhere that it needs to be lined with newspaper or cardboard, but I'm sure the runner would get through or under that.

I really don't know where to start with it, so any suggestions are gratefully received. Thanks.

[Jasey]

I think you could use that plastic garden edging they sell at Bunnings, dig a thin trench and drive it in so it was almost level with the ground; this will stop the movement of soil runners.

[Clinton1]

cooch really needs a 70cm deep continuous barrier, either plastic, concrete, roof sheeting and so on.

Less than 70cm and the runners will go under. Also, the barrier needs to extend above the soil, so you can see runners coming over the top and hit them with some glyphosate (roundup).

It would be an idea to spray glyphosate outside your fence and kill off a strip on the vacant land... slow the runners getting onto your place. Or just poison the bloody lot! :D

Cooch roots go down about 20 to 30 cm, and then send runners out. The runners can go down at least 50cm, diving under barriers to re-emerge elsewhere.

Obviously, creating a 70cm deep barrier has several drawbacks, water movement (you will create a runoff barrier!) is one, the other is the fact that you need to dig a 70cm trench.

Have you considered letting the cooch take over the lawn (its a great summer grass) and just keeping it out of the garden beds?

Cooch is a bastard of a grass... but has its benefits as a summer grass and pretty low on water needs... the trouble is that if your neighbours have cooch, you'll be fighting it forever.
The best way to bet rid of cooch is to have your neighbours fight it off... otherwise, it will be tough getting rid of it from your own patch, either that or choose to welcome it.

[quercus]

In my considerable experience killing couch, the runners tend to be in the top 10 cm of soil, rather than going deep, unless they are disturbed, when they can live deep for a long time. A piece of 25 x 150 mm pine (6" x 1") works ok. As mentioned though, you need to stop the runners coming over, so regular patrols with the roundup are needed. You will need to spray it now though, as it goes dormant in late autumn, and doesnt' take up the roundup very well, even with a penetrant or surfactant added.