The Lulav and Etrog are important elements of the Feast of Tabernacles, also known as Sukkot.
We read in Leviticus 23:40, “On the first day you are to take choice fruit of trees, branches of palm trees, boughs of leafy trees, and willows of the brook, and rejoice before Adonai your God for seven days.” (TLV)
When you put these 4 plants together you then make 1 lulav. Now there is a citrus fruit that is also used, a citron which looks like a bumpy lemon with a protrusion on each end. Six branches are bound together, and the lulav is tied to it making one unit. You can say it makes one Lulav set.
We are to take the 4 plants and use them to rejoice before Adonai our God. We wave it east, south,west, north, up, and down, showing that we understand that God is everywhere. We shout “Hoshanah Rabbah–Please save us!” We then beat the willow branches into the ground at least 5 times shaking loose some if not all of the remaing leaves. It is said that this reason is actually agricultural. For the rainy season begins in the fall. The willow leaves falling from the branches is a symbol of our hope for rainfall.