There is a common custom among Ashkenazi Jews to decorate their synagogues and homes with trees and flowers for the holiday of Shavuot. In this essay, we will explore some prominent reasons for this minhag and try to fully understand the importance of this minhag. 

The earliest known source of this minhag is recorded by the MaHaril, Rav Yaakov Moelin (1365-1427),  who records that on Shavuot, German Jews in his community had the custom to place fragrant spices on the floors of their synagogues for “simchat haregel,” for the pleasure of the holiday. He does not mention, however, the connection between fragrant smells and the chag of Shavuot. The Rema codifies this minhag in Orach Chayim 494:3, where he states the custom of decorating our shuls and homes with green plants and trees as a remembrance of matan Torah. 

Many achronim try to explain why the minhag of decorating with trees helps us to remember matan Torah. 

The Levush explains that the connection between matan Torah and trees is apparent in the pasuk in Shmot 34:3:  

גַּם-הַצֹּאן וְהַבָּקָר אַל-יִרְעוּ, אֶל-מוּל הָהָר הַהוּא. 

The sheep and cattle should not graze opposite that mountain.

At ma’amad Har Sinai we were commanded not to let our animals graze around Har Sinai, and from that we infer that there were many trees surrounding Har Sinai. 

Rabbeinu Sheim Tov Gagin in his Keter Sheim Tov, offers another approach, based on the verse in Shir Hashirim.

לְחָיָו כַּעֲרוּגַת הַבֹּשֶׂם, מִגְדְּלוֹת מֶרְקָחִים; שִׂפְתוֹתָיו, שׁוֹשַׁנִּים--נֹטְפוֹת, מוֹר עֹבֵר. 

שיר השירים ה:יג

His cheeks are as a bed of spices, as banks of sweet herbs; his lips are as lilies, dropping with flowing myrrh.

He explains the words “siftotav shoshanim,” (his lips are as lilies)  to mean that every word of HaShem fills the world with wonderfully fragrant smells. As such, there is a very clear connection between this interpretation of the verse in Shir HaShirim and the minhag as initially recorded by the MaHaril. 

There is a common thread in the various reasons for the minhag. It seems that this minhag is an attempt to recreate the setting of ma’amad Har Sinai on Shavuot. Yet the minhag  demonstrates something deeper as well. Another message can be found in the verse in Parashat Va’etchanan in recalling ma’amad Har Sinai. The verses state, 

רַק הִשָּׁמֶר לְךָ וּשְׁמֹר נַפְשְׁךָ מְאֹד, פֶּן-תִּשְׁכַּח אֶת-הַדְּבָרִים אֲשֶׁר-רָאוּ עֵינֶיךָ וּפֶן-יָסוּרוּ מִלְּבָבְךָ, כֹּל, יְמֵי חַיֶּיךָ; וְהוֹדַעְתָּם לְבָנֶיךָ, וְלִבְנֵי בָנֶיךָ.  יוֹם, אֲשֶׁר עָמַדְתָּ לִפְנֵי ה’ אֱלֹקֶיךָ בְּחֹרֵב, בֶּאֱמֹר ה’ אֵלַי הַקְהֶל-לִי אֶת-הָעָם, וְאַשְׁמִעֵם אֶת-דְּבָרָי:

דברים ד:ט-י

But beware and watch yourself very well, lest you forget the things that your eyes saw, and lest these things depart from your heart, all the days of your life, and you shall make them known to your children and to your children’s children, the day you stood before the Lord your God at Horeb, when the Lord said to me, “Assemble the people for Me, and I will let them hear My words, that they may learn to fear Me all the days that they live on the earth, and that they may teach their children.

Devarim 4:9-10

The Ramban asserts that these verses impose two very important obligations. First, that we must take extra heed to remember the Torah and its mitzvot. Second, that we must remember the experience of ma’amad Har Sinai and pass it down to our children and grandchildren. In light of the Ramban, it seems we have an obligation not only to remember the experience cognitively, but also experientially by recreating ma’amad Har Sinai through sounds, smells and visions. Ramban here emphasizes the importance of the “ma’amad Har Sinai Experience,” including all the sounds and visions, because he felt that the atmosphere of ma’amad Har Sinai, was essential to our internalization of our deep rooted faith in God and His Torah after our close encounter with Hashem Himself. 

Considering this obligation, it is no coincidence that the minhag of decorating our shuls with fragrant flowers and trees is one that is linked to the well-known psychological phenomenon that smells trigger memory. This phenomenon of sensory input causing significant memory recall is called the Proustian phenomenon, wherein by creating a similar atmosphere to one that had been previously experienced, the individual is transported back to that original setting. We use this minhag as an avenue not only for our own fulfillment of re-experiencing ma’amad Har Sinai but also to fulfill our obligation to teach our descendants about the entire matan Torah encounter through experiential education. Experiential education is a tool that is often utilized in Jewish education, such as at the Pesach Seder. However, I believe this minhag of decorating our shuls with greenery is yet another example. By creating the atmosphere of Matan Torah, we can instill into future generations not only the message of the importance of the Torah we received on Har Sinai, but also the experience itself.