FloBear, you asked for suggestions for plants for your 'free range' area of your garden. Would leycesteria formosa (pheasant berry) grow there? It grows tall enough that the hens can't jump up to eat it all, and it has attractive flowers and berries which they love. The only things that have survived in my hens' permanent run is one daffodil, one tulip and a kind of perennial onion.
Our run, about 9 foot square, is three quarters covered with clear corrugated plastic sheets. They have to be tied or weighted down VERY securely or you end up retrieving bits of broken sheet from all over the garden after a windy night!