These are traditionally found both in the home and the synagogue.
Excerpted from Celebrate! The Complete Jewish Holiday Handbook. Reprinted with permission from Jason Aronson Inc.
Synagogues and homes are traditionally adorned with fresh greens and flowers in honor of the holiday that occurs in the spring. Small trees, leafy or flowering plants, boughs, and floral arrangements are placed around the sanctuary and near the ark, as well as around the house and on the dining table.
Favorite flowers for the occasion are lilies--standing in for the lily of the valley to which Israel is compared in the Song of Songs (2:1-2)--and roses, chosen because of a playful reinterpretation of a verse from the Book of Esther (8:14), "the decree (dat) was proclaimed in Shushan" becomes "the law (dat) was given with a rose (shoshan)."Lilies and roses often have been placed directly on the Sifrei (plural of sefer--scroll) Torah, individually, in wreaths, or in garlands.
As an agricultural holiday, Shavuot has always been linked to plant life. In particular, the baskets used to transport first fruits to the Temple were adorned with flowers and leaves. According to another explanation for the decorative scheme, the greens recall Sinai itself. The fact that the Israelites were warned not to allow their livestock to graze near the mountain (Exodus 19:12-13) indicates there was a grassy oasis at its base. The greens serve as vibrant reminders that Torah is "a tree of life to those who hold fast to it" (Proverbs 3:18).
Some rabbis claimed--even though they are in contradiction to the foundation for the holiday of Tu Bishevat--that we use branches because Shavuot is the Day of Judgment for fruit trees. Rabbi Elijah, Gaon (meaning" excellency" or "genius") of Vilna, Lithuania--the leading sage of his era (1720-1797)--tried to have the custom of decorating with flowers and leaves discontinued when similar practices became widespread among Christian churches for Whitsun, the day Jesus' disciples are said to have been divinely inspired (the Christian version of Pentecost, Greek for "50th" and the archaic term for Shavuot).
Despite the admonition of the Vilna Gaon, using plants and flowers to decorate homes and synagogues for Shavuot was fairly widespread, particularly in Europe. Fresh grass was sometimes scattered on the floor of a house, and spices and roses on the synagogue floor, a reference to the midrash claiming that the Israelites had to be revived after fainting out of fear when they heard God's voice. Another midrashsays that the fragrance of spices filled the world as each commandment was issued. Because flowers were used to decorate the Sifrei Torah,in Italy the holiday was called the Feast of Roses, and in Persia the Feast of Flowers.