Continuing its discussion of the arbah minim – the four species that are taken up during the holiday – the Mishna (33b) discusses the requirements of the aravah. Aside from the limitations that we are already familiar with from our study of the lulav and the hadasim (e.g. that a stolen or dried up branch cannot be used), we learn that a tzaftzefa is not kosher for use as an aravah.
What is an aravah and what is a tzaftzafa? The baraita lists that an aravah has a reddish stem and a long leaf with smooth edges, while a taftaefa has a whitish stem and a round shaped leaf with serrated edges. Another baraita distinguishes between different types of serrated edges – when they are like a magal (scythe) they are fine; the problem is when they are shaped like a masor (saw). In fact, Abaye identifies the scythe-shaped plant as a hilfa gila, which was apparently well-known to be considered an aravah.
These identifications do not make the picture much clearer. The commentaries discuss whether all three of the “rules” must be met in order to declare a plant to be an aravah; from the story of the hilfa gila it is clear that not all of the criteria must be met. Furthermore, the Tosefta and the Yerushalmi appear to have variant readings of the baraita that give a very different picture of the kosher aravah.
Thus, even with the lengthy list that the Gemara gives, indicating the ways to distinguish between the kosher aravah and the non-kosher tzaftzafa, it is still difficult to ascertain which types of trees are referred to. It appears that both the aravah and the tzaftzafa are types of willow trees of the salix family, short trees that grow very quickly. Even within the two types there are many varieties, including trees that are grafted and contain both types within them.
The aravah likely can be identified as salix acmophylla boiss, while the tzaftzafa, which, according to the Gemara, has leaves that are of a different shape than the aravah, may very well be the “white willow.”