שולחן ערוך אורח חיים · סימן תרנ״ד

English

That one can return the lulav into water on Yom Tov: A woman can take the lulav from her son or husband, put it back in water, and add water as necessary, though she cannot switch out the water. On Hol Hamoed, it is a mitzvah to switch it out so that [the four species] stay moist and beautiful. RAMA: It is the practice to take a new willow branch each day of Hol Hamoed and attach it to the lulav as a way to beautify the mitzvah.