chickens in orchards

My husband and I would like to allow our chickens to free range in our pranced. Our question is this: will they eat the leaves on our bushes and trees? We already know they will eat the fruit/berries.

I have 6 mature leghorns free range inside a fenced fruit tree orchard of 12 trees. I would like to use a copper or sulfur based dormant spray during the winter but am concerned about the health risks to my chickens or the possibility of the spray ending up in the eggs. Does anyone have...