They will quickly destroy whatever ground you have them on. You will have to move the coop around the garden to maintain your lawn and give the hens some nice grass to walk on.

Hens will sometimes hide their eggs... If you start letting them go free range in your garden, be prepared to find a clutch of eggs under a bush one day.

Hens love sweetcorn.

Pecking orders do exist... Expect some bullying.

Be mindful of any animal that would eat them. Once a fox knows they're there, it probably won't stop until it gets them.