A little more info on the basswood trees...several years ago on my farm I noticed that there were a few trees that got shredded every year and at least one of them was in a very hard to reach spot. I found this peculiar, so I suspected that there was something about that tree that drew the bucks every year. The tree was about 2/3 the way up a very steep creek bank. A buck would have to be part billy goat to rub on it since it was on such a steep side hill, but rub it they did...every year, with a vengeance.
I later looked at the tree while it was still leafed out and determined it was a basswood tree. And then I doubled back and looked at some of the other perennial rub trees and found that several of them were also basswoods. Most of these basswoods were near creek beds FWIW. Note, small to medium sized cedar trees were #2 on the perennial rub list.
So now, I look for basswoods and pretty much can count on them getting rubbed every year.
This past spring I was on a farm tour with a group of hunters that included a professional forester with a degree from ISU. We came up on a clump of basswood trees and every one of them was shredded and the host explained to us that this area was torn up with rubs every year. A couple of us talked amongst ourselves briefly and it turns out that each of us had observed the "basswood phenomenon".