Rockefeller Center Christmas Tree Lighting Ceremony - November 28, 2012 from 7-9 p.m. - On NBC Television
While not officially a National Christmas Tree, New York City's Rockefeller Center Christmas Tree is the biggest, brightest, most famous Christmas tree on our planet. It's lighting is an annual television event. The tree is nearly always a Norway Spruce and grown by enthusiasts hoping for the honor of having their tree chosen to be displayed at Rockefeller Center. The event takes place just after the Thanksgiving holiday weekend.
There is - or are - several official national trees. I am still not certain as to which is the most official, but there are at least four trees that can make that claim: National Christmas Trees - All the Confusion