Hadass

hadassim - הדסים‎) is a branch of the myrtle tree that forms part of the netilat loulav used on the Jewish holiday of Sukkot.

The others are the lulav (date palm frond), aravah (willow), and etrog (citron).

Together with the etrog, the lulav is waved in all four directions, plus up and down, to attest to God's mastery over all creation, and to voice a prayer for adequate rainfall over all the Earth's vegetation in the coming year.

According to the Halakha, the most perfect hadass is one whose leaves grow evenly in each set of three.

[1] Hadass is also used as the "Besamim" or holy spices in some Sephardic and Mizrahi customs for Havdalah.