` ` ! ! '' host Alex Trebek served as parade 's grand marshal . Near the National Mall , large crowds mingled under the branches of the blossoming trees that line the Tidal Basin . Cherry blossom ##s were a gift to U.S. government from Japan in 1912 . National Cherry Tree Festival celebrates the arrival of spring .
` ` ! ! '' host Alex Trebek served as parade 's grand marshal . Cherry blossom ##s were a gift to U.S. government from Japan in 1912 . National Cherry Tree Festival celebrates the arrival of spring .