Here is another instance of visually pleasing wild growth from my daily route to campus, this one spotted in a parking lot at the side of the street.
A climber, this delicate blue-flowered plant is weaving its way through the shrubs at the edge of the parking lot
A close-up of the leaves and flowers
Apparently this is bird vetch (Vicia cracca), a plant originally native to Europe and Asia. It has become an invasive weed in some parts of the country, yet on the other hand it enriches soil by fixing nitrogen - like other leguminous plants - and apparently also makes a good forage crop and can be used to curb erosion.
Sources: Wild Urban Plants of the Northeast by Peter Del Tredici, http://en.wikipedia.org/wiki/Vicia_cracca