see mishna brura 651:14 same thing
Indeed, however there he is not clear that you must leave the top tefach of the Shedra (the part which the leaves come out of) and not just the top tefach of the Lulav (which is what many people do). Although everyone should agree, since as we know the shiur of a lulav is 4 tefachim of shedra - kedei lenanea. So obviously the top tefach of shedra must be left untied (as the reason to leave it untied is kedei lenanea -see kitzur sh"a, although MB is not clear since he says it is לכסכס)
