How do I kill couch grass organically prior to sowing a lawn?

Question

The area of yard I intend to sow as lawn is around 150sqm, and has just been levelled by machinery which removed much of the plant material. Most parts of it have just had a shallow layer scraped off the surface though and there is couch (aka twitch) established in perhaps a third of the total area. In the parts where the level had to be raised, I expect some broken couch stems will be mixed in and will sprout.

After initially trying to dig out some of it, I've realised the full extent of it so I'm interested in a larger scale solution. Any tips would be appreciated!

I don't want to spray it with herbicides, so I'm looking for a solution consistent with organic gardening philosophy.

Answer 1

Quack grass has many common names but the Latin name is Elymus repens.

From this page I see that solarization will not work as the plant is perennial and the seeds are tough. Recommendations for farmers suggest plowing in the fall to bury the rhizomes further down where less will resume activity in the spring. This is not practical for a homeowner.

I do see phrases such as

A good, thick, well-composted and well-watered lawn will smother it, and so will a thick mulch, or a carpet, though it will take time. To control couch grass on a lawn, mow higher -- set the mower to more than 3 inches.

and it appears that regular turf grasses respond better than quack grass to fertilizing.

For areas where there is no sod expect this solution to take all summer:

• rototill and remove root fragments, after the sun has baked anything on the surface repeat at least two more times
• add a few inches of good compost or weed free topsoil and sod in the fall
• apply a fall fertilizer and a spring early green up fertilizer
• cut the grass high, over three inches (scythe anyone?)
• do not let the grass go dormant over a hot summer due to drought, water to keep the turf going

The second option is to cover with landscape fabric or cardboard and a thick mulch for a year. Less labour but the area is out of commission for growing for a year.