Christmas Cactus

While we were having our appetizers with the keeper and her guests, we noted that the Christmas cactus was blooming.  How does it know how to do that with such precision?
Pretty impressive.  We also listened to a beautiful CD of the choirs of the Cloister School of St. Ursula from the Black Forest area of Germany.  W's friends who visited this summer sent it to him for Christmas. It was beautiful.  We listened to it twice.