The East Boston Urban Frou-Frou Tree?
Seriously though, ornamental trees that are not native can cause serious problems later on. In Florida, the Black Olive and Melaleuca were planted as ornamental trees along sidewalks, and developed into real pests. The Black Olive drops nasty berries on your car and ruins the paint job. The Melaleuca and Brazilian Pepper are so invasive that they have to strip the land down to the bedrock to get rid of it.
Whatever it is there on your sidewalk, it will not be a sapling forever, and could become very big, dropping greasy staining flowers on your car, ripping up the sidewalk with its roots, and probably sending its seeds into your yard.
This is what happens when politicians think they are horticulturists.
Great veggie garden, by the way! I remember the pics you posted last year.
Well, up here it is more that of Maple trees getting so big after many years that break up sidewalks, and with all the colleges around here they have plenty of knowledgeable help on trees. However, when it comes to social problems, it seems that many think money grows on trees.