I have a bur oak tree that I planted about four years ago when it was a sapling, and I was surprised that it had some acorns on it this year. I always thought it was supposed to take 20-30 years before they start getting acorns, but that might just be for red and white oaks. I've got the bur oak in my yard and the deer always seem to rub on it every fall, so I put four fence posts around it and two heights of cages that I made out of old fence. How long do some of you usually leave protection around the trees? All the trees I've planted in the yard during the past five years have at least a couple of fence posts around them.