[MarkusQ]

But it's a reticulating structure; yes, the graph is directed / partially ordered, but it's certainly not tree-like.

The key property of real trees is that they _branch_ and the branches don't recombine.

[garrettgarcia]

Au contraire: https://en.wikipedia.org/wiki/Inosculation

I do agree that branches staying separate is the essential property of a tree data structure.

[Retric]

That’s referring to a joining between different trees not the same tree.

The need to connect leaves to roots is what gives individuals trees their branching nature. Obviously a tree can have holes in it etc, but loops in nutrient delivery present an inherent issue.

[aidenn0]

Which is why the article points out that it's a directed acyclic graph, not a tree.