How long after Roundup can I seed?

I have several large light green patches in my lawn that appears to be a different grass. It grows slower than the rest and looks unsightly. Covered in my thread here.

I have decided to just kill it and reseed those patches, so about three weeks ago I applied glyphosate (Roundup Optima +) and it appears to be working, albeit slowly; the grass in those patches is yellowing. We didn't have any rain (remarkably!) for a couple of days after I applied it so it should be doing it's job.

Assuming that in the next week or two it has killed the grass, I intend to rake out the dead stuff, apply a light covering of top dressing and then seed.

Is that an okay timescale for the Roundup to have left the soil? I obviously won't be seeding until the very end of March at the earliest.

 

According to the instructions you can replant next day, though a bit surprised its taking so long for the grass to die off, probably being so cold at the moment.

Having just seen your other post we do wonder if reseeding those specific areas will make you pleased as in our limited experience of patches like that, even with new seed or new turf it will always look a bit different in colour to the surrouding lawn.

We would try this method on a patch in late spring once the grass is actively growing.

Dig out the old grass and soil and refill with similar soil from one of your boarders.
Using something like a small bulb planter, take a few cores of grass from other areas of good lawn and plant them into the patch, they do not need to touch.
Within a few weeks they should quickly grow and knit together and hopefully be a good growth and colour match to the rest of the lawn.

 

Excellent advice, thanks Ricky. I poweraked and overseeded the whole lawn in the autumn, and as the raking ripped out most of the grass the overseeding growth is pretty much the entire lawn now. Annoyingly the patches of existing grass that remained after raking included these light spots. I was hoping that the overseeding would crowd them out but they seem very strong!

I was planning to use the same seed and hope for a match.