The Great Hedge Bedstraw (Galium mollugo) grows in hedges but also on roadsides and hayfields. After mowing the grass and some rain the white clouds will re-appear.
Like other bedstraws this one has tiny, star-shaped flowers. Insects search them for nectar.
All bedstraws and other members of the Rubiaceae-family have verticillate leaves. In the Great Hedge Bedstrow they are now hidden under the great mass of flowers, but in spring they looked like this.

