How to automatically manage label position?

Looking at the documentation for the treeplot command, I can't help noticing that the author somehow managed to set the node labels of the tree plot with minimum conflict with the other elements of the plot:

For example, the root label ('1') is placed on top of its node while labels '2' and '3' are set respectively on the left and at the bottom of their nodes. Thus avoiding to step on the markers and lines of the plot.

Can this be done systematically for any node/label or do I have to "manually" adjust each label (HorizontalAlignment, VerticalAlignment, etc.)?

Edit: As far as I understand, the labels are added as described here .