Yosef Karo

“ Most of this species grows by streams, which is why it is called "willows of the stream." Even if it were to grow in the desert or the mountains, it is valid. There is another species similar to the willow but with round leaves with edges serrated like a massar (meaning a sickle, siga in the vernacular) and a non-red stem. This is the tzaftzfa, and it is invalid. There is a kind of willow whose leaf edge is not smooth but rather has many small protrusions like a small sickle, and it is valid. ”