Source : Wiki Commons / Bruce Marlin . A 40-year old Quercus bicolor at the Morton Arboretum. Over the weekend, 16 swamp white oaks ( Quercus bicolor ) arrived at the 9/11 Memorial Plaza site. This morning, the trees were planted and by the time the memorial is completed, a total of 400 of trees will have been planted. The swamp white oaks were grown at a nursery in Millstone, New Jersey. One of the criteria for tree selection was that the trees come from a local source, according Ula Ilnytzky of the Associated Press. Environmental Design, a tree transplanting and preservation company in Houston , has responsibility for the plaza's trees. The plaza was designed by Peter Walker Partners and Landscape Architecture and Michael Arad of Handel Architects . Of the trees, 9/11 Memorial Chairman Mayor Michael R. Bloomberg said "The planting of the first trees on the Memorial marks a special moment in the rebuilding of the World Trade Center. Over this next year, the tre