Judith in England wrote:

I am sowing some wild flower seeds in a spare lawn - not exactly a wild-flower
meadow - but a small similar.

I'm guessing that it depends quite a lot on the variety.
I know from talks over here that a wildflower meadow is a highly localized
thing; the varieties and their proportions will vary over surprisingly
short distance.
The Seed Saver's Exchange headquarters farm in Iowa/North central U.S. is
restoring some wild meadow to spaces that flood too frequently to be used
for other plantings, and they spent a lot of time researching what to
plant. In the end, of course, Mother Nature will do the final sort.

--
Gary Woods AKA K2AHC- PGP key on request, or at home.earthlink.net/~garygarlic
Zone 5/4 in upstate New York, 1420' elevation. NY WO G