One day on the forums at permies.com, I came upon a post inquiring about how to make what's commonly called snow fence, beach fence, or sand fence. You've probably seen it before - it comes in a roll and is made out of thin pickets of wood held together with several strands of wire.
Further down in the thread, someone posted a video of a simple machine for making such a fence. It's pretty brilliant: https://youtu.be/PhzXu9pk2co Apparently these machines were quite popular in the latter half of the 19th century, before multi-strand woven wire fencing was invented.
So I saw that video and figured I could make the same thing, but scaled up for 8 foot tall pickets, so as to keep the whitetail deer out of my tree plantings. So I got on nitrochain.com and ordered some sprockets, idlers, and chain, and I went to my local steel supplier for some square tubing. A short while later, I had put together a super duper fence machine.
The effect of fencing the field was pretty dramatic. Previously the deer had eaten off all the newly sprouting woody plants. Now every year among the grass I find new wild seedlings of things like apples, asparagus, daisies, chokecherries, and more.
When putting cages around individual trees, there comes a point where the amount of fencing used for the tree cages surpasses the amount it would take to fence the entire area. For my 5 acre parcel, the length of the perimeter is 1998 feet, which is the equivalent of 212 three foot diameter tree cages. That might sound like a lot of trees (it is), but it's a drop in the bucket compared to how many trees I want to have when I'm old. And in fact, across the various orchard rows and hedgerow plantings, I've planted thousands.
So... the moral of the story is to paraphrase the memorable line from the movie Field of Dreams: "If you fence it, the trees will come."