What prompts the cherry blossoms to bloom?

Washington Post : As Washington, DC, celebrates its National Cherry Blossom Festival this week, the Post‘s Brian Palmer interviewed Ove Nilsson of Sweden’s Umea Plant Science Center concerning the genetic basis for when the plants bloom. According to Nilsson, the blossom festival started last June, when the buds were actually initiated. The longer days of summer kick-start the growth processes by allowing a molecule in the plants’ cells, the FT protein, to be produced. Winter’s shorter days signal the plants to go dormant. In the spring, however, it is not the longer days but rather the warmer temperatures, Nilsson has found, that signal the blossoms to open. Thus global warming could challenge the system, for two reasons: It could throw off the plants’ ability to sense spring and disrupt the pollination schedule of bats, birds, and bees, which spread the plants’ seeds.