I have put in a request for a street tree in front of my house, and it has been approved. This is part of the program TreePhilly, a part of Philadelphia Parks and Recreation, which seeks to plant trees in yards and streets in Philadelphia. In this program, people can request trees to be planted in front of their homes, and these trees would be good for the environment; they would also provide shade in the summer (and who would be against that?) and they help raise the value of property.
For further information, contact treephilly.org, or contact Philadelphia Parks and Recreation at (215)685-4362 or (215)685-4363.