No matter how unique the individual gardens are, conforming street trees really unify a neighborhood. Streets of tract homes are typically planted with a common street tree that is complimentary to the architectural styles of the homes, and is complaisant to the difficulties of life at the curb. Neighborhoods of mixed architectural styles sometimes have difficulty finding a tree that suits every home, so often select two or more options. Older neighborhoods are not quite as selective about conforming street trees because so many various trees get mixed in over the years.
Before selecting a street tree, it is best to inquire with the particular municipality about designated street trees. Home owners associations generally install their own trees where needed, with little or no regard for the preferences of individual residents. Some urban neighborhoods (that are not home owner associations) are nearly as selective, requiring individual home owners to maintain a specific street tree or trees. Others do not require street trees, but limit selection for those who desire them. Selection is very often limited to only a single species.
There are of course many rural and unincorporated neighborhoods without limitations for street trees, and neighborhoods where limitations simply are not enforced. However, selection should still be limited to trees that are appropriate for curbside planting. Such trees should have high branch structure so that they can be pruned for clearance above the largest of trucks that can use the roadway. They should be reasonably clean, and not produce anything that could be messy on cars parked below. Roots should be complaisant with concrete curbs and sidewalks, particularly where space is limited. Foliage and bark must be resilient to harsh exposure and enhanced glare (from surrounding pavement).
London plane (sycamore) and crape myrtle trees are the two most common street trees planted by landscapers, and are the most commonly pre-designated street trees, but are actually not the best of choices. London plane is popular among landscapers because it can survive the neglect that landscapers are notorious for, but has aggressive roots that eventually damage concrete, especially since landscapers waste so much water and keep the soil saturated. Crape myrtle is remarkably colorful both in bloom and with fall color, and has remarkably complaisant roots, but does not get tall enough for adequate clearance, and often gets infested with insects that drop sticky honeydew on parked cars.