Any idiot knows a tree has a branching structure, or at least that's what we've been telling the first years since time immemorial. There was a proper CS tree at UNSW back before I got there that the internet doesn't appear to remember so well. This photo of the "right way up" fig is from Geoff Whale's data structures textbook, and carries the following attribution:
Evidence that trees sometimes really are as shown in data structure textbooks. Sculpture using the medium of a dead fig tree at UNSW. Photo by Russell Bastock.
I reproduce it here without permission. That must be the Applied Science building in the background and my guess is that it sat at the eastern end of where the Red Centre is now.
I spotted this purported "tree" on Centennial Avenue, near Avoca St (which runs between Queen and Centennial parks) several months ago but have only now got around to photographing it. I grant that it appears to be a DAG, and is therefore for most purposes a tree.