The BBC covers it nightly and among the bounty of blossoms is a visit from the Queen herself. The Chelsea Flower Show is renowned as the most prestigious flower show in the world, and special are the show gardens on the Main Avenue. Like the Christmas windows at Bergdorf Goodman, they take a year—or longer—to plan. One garden wins, followed by medals for four top contenders. Admission is limited due to the size of the grounds, so tickets must be purchased in advance. —L.J.