In Shulchan Aruch the Rema mentions an apparently innocuous and lovely custom. The custom is to decorate the synagogue and homes with greenery on Shavuot.
As lovely as the custom sounds, the Gaon of Vilna zt”l opposed it and it has indeed fallen out of practice in many Ashkenazi communities.
In this meeting we will discuss the reasons given for this custom and the reason that the Gaon of Vilna opposed it.