The Torah requires us to take on Sukkot “the fruit of a goodly (hadar) tree, date-palm fronds, a bough of a leafy tree and the willows of the brook” (Lev. 23:40).
The date-palm fronds and the willows are the easiest to identify. But what is the meaning of the “goodly tree” and the “leafy tree”?
The sages reasoned that the goodly tree had to be the citron (etrog), since both the tree and its fruit were pleasant to the eye.
This excluded, for example, the pomegranate, since its fruit was beautiful but the tree was not. Nor could it be the carob tree, since the tree was impressive but not the fruit.
How about the “leafy tree”? Many trees in Eretz Yisra’el were leafy.
The rabbinic sages said the leaves had to cover the trunk, which did not apply for example to the olive tree. The sages identified the leafy tree with the myrtle.
They saw too that – apart from the technical requirements of the text – the myrtle was especially versatile in that it contributes a range of products to the medicinal well-being of the human race.
In the view of Maimonides, the Four Plants not only teach us the ethical lesson that all types are part of the community, but historically they demonstrate that the chosen plants are symbols of leaving the desert behind and entering the fertile Land.
Samson Raphael Hirsch regards the Four Plants as representative of the main four categories of vegetation, so that a Jew who takes the Four Plants testifies that the whole world belongs to God.