Chickens with access to fresh greens is a good thing for both you and them. The nutrients provided by the vegetation ends up in their eggs and meat. Also, fresh greens can make up to 20-30% of a chicken's diet which reduces feed costs.

Sometimes based on your circumstances supplying your chickens with something green to nibble on can be difficult. When chickens have lots of room they'll graze a little off the top and carry on. When their space is limited, as in a small backyard, chickens will ruthlessly tear apart the ground beneath them. Putting a mesh over garden beds is a good way to keep chickens from ripping apart the ground yet giving them access to fresh greens.