NUTCRACKING AT 50: Fifty years ago, George Balanchine on Feb. 2, 1954, to be precise, first staged his own production of the Tchaikovsky ballet “The Nutcracker” at City Center. It was a little late for Christmas that year, but it very soon found its rightful place both in the calendar and in the hearts of New York children – especially after 1964, when the company moved, with a new production, to Lincoln Center. It has been the most popular work Balanchine ever created, an annual subsidy/meal-ticket for his ballet company, and, of course, the Christmas show of all Christmas shows. Balanchine himself had first danced in “The Nutcracker” as a child, while a student in St. Petersburg, and fell captive to its special crystal magic: the warm cheer of its Christmas party, giving way to a world as cold as a snowflake and as sweet as a sugarplum, a Christmas fantasy complete with a tree that grows as high as the sky. New York City Ballet opens its 50th anniversary season of “The Nutcracker” tonight with the first of 45 performances. Tonight the ballet is to be led by Maria Kowroski as the Sugarplum Fairy, Charles Askegard as her Cavalier and Sofiane Sylve as the Dewdrop Fairy, but over the season there will be a multiplicity of casts. Interestingly, a few of these will come from the junior ranks of the company, for traditionally City Ballet has always used “The Nutcracker” holiday season to occasionally test out a select group of its most promising upcomers. New York State Theater, Lincoln Center, Broadway at 63rd Street; (212) 307-4100.