Grassing over a flowerbed

Good morning,

we are in the process of clearing a significant amount of ground elder from our large flowerbeds.  We are planning seed/turf one of the beds because we need a bigger lawn.

i am trying to avoid chemicals so we are digging the ground elder out and thinking of using a high quality weed control fabric until March next year.  Will this allow us to lay a lawn next year say in March/Apr or would laying the fabric for just the summer/early autumn be enough?  I ask as our  previous new lawns have done better when they have been laid in the autumn.

hints and tips gratefully received!