The Gemara explains that the reason we use a shpod shel rimon in the roasting of the korban Pessach is that it does not give off moisture and does not conduct heat.
But it is surely not unique in this respect- certainly other shpods considered in the Gemara would conduct heat or give off moisture, but what about for instance an earthenware shpod? Is there an inyan that the shpod davka be shel rimon, or could we in fact have used any shpod which neither gives off moisture nor conducts heat?
Daniel Moskovich, Kyoto, Japan
The Meleches Shlomoh (Pesachim 7:1) is Medayeik from the Rambam (Korban Pesach 8:10) that Rimon branches are not le'Ikuva. It seems that the amount of liquid that other branches exude is not significant enough to cause the Korban to be considered Mevushal.
Similarly, it is possible that we could find other wood that is suitable. However, the fact that the Gemara asks on the Mishnah why it specifies Rimon would seem to indicate that the Gemara assumed that le'Chatchilah Rimon is the preferred type.
It seems that the Gemara is seeking a reason to explain why Rimon is more suitable than others, even those not mentioned specifically in the Gemara. Possibly it gives off less liquid than other types of branches. As for earthenware, I believe that it is a better conductor of heat than wood, which would give wood the edge.
It is also possible that we may find other materials that are as suitable as Rimon branches, but less convenient. For example, if earthenware were to be used it would present problems of Kashering from the B'lios which would become Nosar, and a new one would be necessary each year, involving unnecessary cost. Rimon may also have a practical advantage over certain other trees in that it is (at least nowadays) readily available in the Jerusalem area.