With what may we bind the aravos branches for Hoshano Rabboh?
Kitzur Shulchan Oruch 138 (2) says one should use leaves of the lulav. Is that all? How about a rubber band?
Some say that the aravos for Hoshana Rabba should not be tied together at all (Magen Avraham 664:8, brought by Mishna B'rura S"K 17), however the Mishna B'rura rules that the prevalent custom is to bind them together. Regarding what may be used to tie them, some hold (see Pri Megadim A"A S"K 4) that only aravos stalks should be used, as anything else would be a considered a chatzizta (barrier). [Using arovos should be fine because min b'mino eino chotetz; the same species is not considered a barrier]. However the Magen Avraham (S"K 4) permits using Lulav leaves to bind, because anything that is to beautify it is not a chatzizta. Although common practice is to use rubber bands, according to the above it would seem problematic.