One of the first things that has struck me as I've begun learning about trees is that they're an alien lifeform with many bizarre characteristics. But they're also like people.
The first way in which I noticed trees are like people is that they are difficult to classify. The leaves of oak trees look a certain way--but not always. Most have lobes, but a few do not. Most birch trees have peeling bark. But some are smooth. There are some trees on campus here (I suspect they're Coast Live Oak, though I may be completely wrong) which are clearly the same type of tree--except for one, on which the leaves are a bit different. Is that just because of its age? Is it a different sub-species? Or does it have just a small genetic difference within the realm of expected variation for its species?
Which brings me to the second observation about how trees are like people. It takes a long time to really get to know them. You may have to observe a tree over a long period of time even just to be able to identify it. For example, I'm not sure whether those trees on campus really are live oak because I don't know what kind of seed/fruit they produce. If they're truly oak, it will be an acorn. If they produce some other kind of thing, I'll have to make another guess.
It's odd--the fact that trees are difficult to classify, and that they take a long time to get to know makes them seem more worthy of respect and admiration. They aren't just a "thing," they shouldn't be treated like mere objects. I guess they're not really a "thou" but they're more than an "it"--wondrous, strange living beings.
And to think I've gone so long without really noticing them very much!