If my Aravos have turned black (because they dried out) are they still kosher to use for Daled Minim, or do I need to buy new ones?
It is still Kosher as long as the top two leaves as well as most of the leaves are still intact. If the top two leave aren’t intact, it is still Kosher, but some are Mehader to have them intact.
It is proper to switch the Aravos sometime during Chol Hamoed.
.ראה שו״ע אדה״ז תרמז
.נקטמו העלים העליונים – שו״ע שם ב. משנ״ב י
.להחליף הערבה – ראה ס׳ המנהגים מנהגי סוכות