Clue #2

(10) In remembrance of the joy of receiving the Torah: for there were grasses around Mount Sinai, as it says "The flocks and cattle shall not graze..." Latter sages wrote that in places where it is the custom to give out fragrant grasses in the synagogue, they should not give them out from Barukh SheAmar until after the Amida, so that one may bless over them (the blessing for fragrant vegetation)-- because during that period it is forbidden to interrupt (the prayer). There is a custom to stand trees in the synagogues and homes in remembrance that on Shavuot judgment takes place for the fruits of the tree. The Gr"a abolished this custom because now it is the ritual of the (non-Jewish) nations to put up trees on their holiday.