Seeds After Weed Killer

[foxhaven]

If I use Roundup weed killer on an area of lawn how long should I wait before sowing wildflower seeds ?

[Buenchico]

Glyphosate (which is present in Roundup) has a half-life of about a month and several half-lives (perhaps 3 or 4) are required before the level of glyphosate can be regarded as 'very low', so you might find that it's OK to sow seeds in the area after 3 or 4 months:
http://www.monsanto.com/glyphosate/documents/glyphosate-half-life-in-soil.pdf

[foxhaven]

okay - no good for sowing seeds for this summer then.
Is there any other way to remove grass ?

[Buenchico]

See 'Ground preparation' here:
https://www.rhs.org.uk/advice/profile?pid=436

However, given that you'll want to plant the seeds in the near future, the only way you'll do it (without having to wait for several months, when it will be too late to sow anyway) is simply to dig the grass up!

[alavahalf]

Why do you need to kill the grass ... why not cut it short and then rake the surface and tear out the bulk of the grass roots. Scatter a fine layer top soil over the area and then sow the flower seed on top of it ?

[foxhaven]

Thanks everyone, I will be getting it sorted soon - seems like I will have some work to do.

[Chipchopper]

It can be a long and difficult process, in getting wildflowers to become established in a lawn, unless you start from scratch to suppress the competition with the grass.
If its a wildflower meadow, you want to create, a short-cut to getting plants established, might be to lay some 'Wildflower turf' or 'Meadowmat' but this will evolve rotorvating or digging out what grass you have.
I haven't tried the meadow turf personally, but I think it may be worth your while investigatig.