boughs of, were to be carried in festive procession on the first day of the feast of Tabernacles (Le 23:40). This was probably the olive tree (Ne 8:15), although no special tree is mentioned.
and ye have taken to yourselves on the first day the fruit of beautiful trees, branches of palms, and boughs of thick trees, and willows of a brook, and have rejoiced before Jehovah your God seven days.
and that they proclaim and cause to pass over all their cities, (and in Jerusalem,) saying, 'Go ye out to the mount, and bring leaves of the olive, and leaves of the oil tree, and leaves of the myrtle, and leaves of the palms, and leaves of thick trees, to make booths as it is written.'