Just re-read this thread and noticed the confusion over the state of grass air fields. The Luftwaffe's role in the early stages of an offensive was to support the army who were making rapid advances. They often found themselves operating literally from fields rather than prepared air fields.
I've attached a photo of a Bf109E-3 of III.JG 51 to illustrate the point.This is May 1940 as the Germans unleashed their Blitzkrieg on France.
Steve