Trafalgar Square Authority in conjunction with the charity Unicef, who began ticketing the event to control crowd numbers. A Christmas ceremony has been held in the square every year since 1947. A Norway spruce (or sometimes a fir) is presented by Norway's capital city, Oslo as London's Christmas tree, a token of gratitude for Britain's support during World War II. (Besides war-time support, Norway's Prince Olav and the country's government lived in exile in London throughout the war.) The Christmas tree is decorated with lights that are switched on at a seasonal ceremony. It is usually held twelve days before Christmas Day.
Christmas tree cultivation urine samples. The average Christmas tree receives roughly a half of an ounce (14 g) of pesticide over its lifetime. The BBC's "Gardening" website called buying Christmas trees directly from the farm, "the most environmentally friendly way of getting a tree". Other positive environmental attributes have been given live Christmas trees as well. Researchers at the University of Nebraska included the reuse of natural Christmas trees as mulch and, in larger quantities, piled up as soil erosion barriers, among the benefits of live tree use. Other positive reuses included fish habitat in private ponds and backyard bird feeders. Since 2004,