It is not often that Mayor Thomas M. Menino can be found mingling with the Radio City Rockettes, Grover of Sesame Street and Santa Claus, along with thousands of onlookers.

But that is just what he will be doing at the 63rd annual Boston Holiday Tree Lighting ceremony, which takes place on the Boston Common this Thursday at 7 p.m.

Looming over this unique collection of celebrators will be a 40-foot spruce tree, shipped down from Halifax, Nova Scotia.

The tree comes as a generous showing of thanks for the relief effort Boston provided with supplies and volunteers when the French ship “Mont Blanc” exploded following a collision in the harbor of Halifax in 1917. The ship, which was carrying ammunition and 400,000 pounds of TNT for World War I, blew up 20 minutes after the crash in a thundering explosion, killing and injuring thousands of onlookers and crew.

Every year since 1971, the Haligonians have not only donated a giant tree to Boston, but paid for the cost of electricity for keeping the tree lit as well.

This sort of goodwill follows along with the tone of the event, which is usually followed by caroling.

The ceremony will also be broadcast on local television stations.