The definition of "architecture" I am using here is from Halle, Oldman, and Tomlinson's classic Tropical Trees and Forests: An architectural analysis (1978) see here. Architecture is "the visible, morphological, expression of the genetic blueprint of organic growth and development."
A good place to start getting you eye trained to look at the architectural patterns of trees is the Lincoln Park Conservatory!
Notice below the way in which space is densely filled in the conservatory. This emerges for a variety of reasons, one of which is that there is a greater number of architectural models expressed in tropical vegetation. This allows for a greater occupation of space for tropical vegetation.
Tropical forest hosts many palms which are characterized by their single trunk often with a single apical meristem. Rare to find these in the temperate zone.
Contrast these conservatory pictures with tree vegetation in the park outside. Architecturally there are fewer models represented. As far as I can tell there has not been much done work done to assess the diversity of these forms in the urban environment.
Oz Park, where there is an attempt made to add a nice understory to the urban forest.
The model analysis can be applied to vegetation other than trees. Here is a liverwort with some nice branching patterns.