May one pluck leaves from a Lulav that is no longer being used [i.e. after Hallel on Hoshana Rabbah] for the sake of binding the Hoshanos, as accustomed? [1]

If the spine of the Lulav is very short or has exactly 4 Tefach of spine, then leaves may not be plucked from it.[2] If it is longer, then it is disputed amongst Poskim[3] as to whether one may peel off leaves from the Lulav, even if 4 Tefachim of Lulav spine will remain, and practically, it is best to make a Tnaiy before Yom Tov that he may remove leaves from the Lulav for the sake of making knots.

[1] See Michaber 665:1; Admur 649:20; M”A 649:19 and Machatzis Hashekel there; Tosafos Sukkah 46b; Daas Torah 651:4; Eitz Hasadeh 650 7; Luach Eretz Yisrael Tukichinsky; Nitei Gavriel 40:24; However, see Kinyan Torah 5:70 who argues that it is forbidden to be done even past the four Tefach mark; See Piskeiy Teshuvos 664:4 and footnote 16

[2] The reason: The Daled Minim are considered designated for their Mitzvah for the entire seven-day period of Sukkos [and even Shemini Atzeres in the Diaspora due to Sfeika Deyoma] and thus ideally may not be used for other purposes until after Yom Tov Achron. However, some Poskim rule that this is only true regarding the minimum Shiur of the Daled Minim, as past the minimum Shiur it was never designated for a Mitzvah and therefore may be used as one wishes. [Poskim ibid]

[3] Luach Eretz Yisrael and Nitzei Gavriel ibid rule leniently based on M”A and Machatzis Hahsekel ibid, however Kinyan Torah and Piskeiy Teshuvos ibid argue and rule it should not be used