Festival of the First Fruits (Bikurim) According to the Mishnah:

The Shavuot festival marks the beginning of the first fruits season, which goes on until the winter.
“How does one designate the BikKurim [first fruits that must be brought to the Temple in Jerusalem and given to the Kohen]? A person goes to one’s field and sees a date that is bearing fruit, a bunch [of grapes] that is bearing fruit, or a pomegranate that is bearing fruit, ties it with a string and says: “Behold these are Bikkurim.”
How do they bring the Bikkurim up [to Jerusalem]? All the cities of a Ma’amad would go into the city of the Ma’amad and sleep in the streets of that city without going into the houses. When they arose, the supervisor would say: “Arise! Let us go up to Zion, to the house of the Lord our God!” Those who were close would bring dates and grapes and the far ones would bring dried figs and raisins. And a bull would go before them, its horns plated with gold, and it would have an olive wreath around its head. The flute would play before them until they got close to Jerusalem. Once they got close to Jerusalem, they would send ahead of them [a messenger] and adorned their Bikkurim. The overseers and officers and treasurers would go out to greet them, according to the stature of those coming in would they go out. All the artisans of Jerusalem would stand before them and greet them: “Our brothers from so-and-so come in peace!”

The flute would continue playing before them until they arrived at the Temple Mount. Once they arrived at the Temple Mount, even Agripas the King would carry his basket on his shoulder and enter until he reached the courtyard. Once they got to the courtyard, the Levites would speak in song (Psalms 30:2): “I will extol you, O Lord, because you have raised me and not allowed my enemies to rejoice over me.”

(Mishnah, Bikurim, Chapter 3)

 

Festival of the Bikkurim in the [Jezreel] Valley Kibbutzim

Over the years in exile, the holiday was emptied of its agricultural content, with only a distant echo remaining through various traditions and customs. This is probably the origin of the custom, toward the holiday, of decorating the synagogue and home with greenery, flowers and branches.
Some would decorate with an abundance of flowers, or scatter rose petals over the Torah scrolls.
With the return of the people to its homeland, with its fields and gardens, vineyards and orchards – old-new content has been added to the holiday celebrations. In the schools and settlements built after the First World War, teachers with their students invoked the memory of bikkurim
dedicated to the Keren Kayemet LeIsrael. The kibbutzim of the Jezreel Valley, on whose dried swampland the first fruits of the harvest grew, was where the Shavuot, the harvest festival and the first fruits festivals emerged.

Celebrations of the Valley People

This is how the people of the valley celebrated in 1923, the day after Shavuot:
”On Sunday there was a procession, from Ma’ayan Harod to Kfar Tivon (Kfar Yehezkel): At the head of the procession, a lamb and a foal adorned with ribbons were led, followed by all the wagons with the first fruits accompanied by riders. The members of Ein Harod, Geva and Kfar Tivon closed the procession. Until sundown, the time was spent dancing and singing on the threshing floor in Kfar Tivon.

The National-Historic Significance

The Book of Deuteronomy gives the agricultural aspect of this holiday clear national-historic significance, with the demand for a personal declaration in this spirit when lifting the basket of fruits. This is the “first fruits exclamation”:
“A wandering Aramean was my father. And he went down into Egypt and sojourned there, few in number, and there he became a nation, great, mighty, and populous. And the Egyptians treated us harshly and humiliated us and laid on us hard labor. Then we cried to the Lord, the God of our fathers, and the Lord heard our voice and saw our affliction, our toil, and our oppression. And the Lord brought us out of Egypt with a mighty hand and an outstretched arm, with great deeds of terror, and with signs and wonders. And he brought us into this place and gave us this land, a land flowing with milk and honey. Behold, now I bring the first of the fruit of the ground, which you, O Lord, have given me.”

(Deuteronomy 26:5-10)

This is just the beginning of the Bikkurim season

The Shavuot holiday is just the beginning of the bikkurim season, which continues until Chanukah. Actually, most of the people would bring its first fruits while making the Succoth pilgrimage.