Burls

 A "burl" is a knotty growth on a tree.  Artists make bowls and other art out of them.  Today, while walking, there was a sign that I thought was just an old broken down sign.  However, as I got closer to it, I realized that it was a burl that was beginning to grow over the sign.

Further along the walk, I thought I saw a sign very high up on a tree.  I thought it was a sign because it was perfectly round.  I also wondered who could read a sign that high up.  Again, as I approached, the sign turned into a burl, the largest I have ever seen.