I recommend either electric poultry fence, or just poultry fence. The electric fencing mesh is more expensive, but it protects the hens better. You can also move it so the poor chickies aren't stuck in one place all the time. In fact, YOU HAVE TO MOVE IT. This is one drawback - but, it doesn't have to be much, just a foot over to a freshly mowed strip. The taller grass interferes with the current in the fence. We got ours from Premier One . . . they have an installation video and demonstration online, as well as lots of feedback from people. I imagine there are other good brands, that is just the one we found. The great thing about it is that shipping is free, and once it comes you can have it up and running in an hour -- no fence post holes, no rolls of wire, no nailing . . . it is lovely. The drawback is that it is expensive - especially if you need a good charger, and I highly recommend a GOOD (ie - expensive) charger if you decide to go with an electric fence. The cheaper feed store models just don't have the oomph for all the wires in the fences.
If you are very sure that there are no predators (stray dogs, coyotes, foxes, opossums etc ) in your area, you could try just the poultry netting. It does the same thing, but doesn't have electricity. I haven't actually used it myself, but I imagine that once the chickens get used to it they would just stay in their area. I had to clip several determine hens wings but now everyone is used to the electric fence and they leave it alone. I think they all got shocked at least once -just startled them.
Here is a picture of our fence around our orchard. I moved it the next day - so you can see the grass was getting a bit shaggy. Here in the Pacific North West, I have to move it every 3 to 4 days, but it would vary depending on how much the grass grows I imagine. Moving it takes anywhere from a half hour for two people if I am just mowing a path along it, and moving the fence over to the cleared spot to an hour or more if I am relocating the pasture to a fresh area. And it is really a job for two people, no matter what the website tells you
We are working on a permanent fence but this has worked VERY well since we got it. It does keep all the chickens in - even my little banties.
Hope it helps! I think they sell the plain poultry netting at feed stores and large hardware stores . . .