New York City ? After nearly nine years, life is returning to ground zero in a tangible way.

Crews Saturday began planting 16 swamp white oaks at the World Trade Center site. They are the first of nearly 400 trees to be planted around the eight-acre memorial to the nearly 2,800 people were killed when terrorists attacked the twin towers on Sept. 11, 2001.

The trees will dot a cobblestone plaza surrounding two huge pools built on the footprints of the destroyed towers.

Joe Daniels, president of the 9/11 Memorial Foundation, was on hand at the site to help with the planting. He said designers of the memorial envisioned a lush and quiet green space that would bring solace to visitors.