Yes, saag freezes beautifully! You can store the leftover saag (with or without the tadka) for a week (6-7 days) in the refrigerator. Freeze for longer use in a freezer-safe container or ziplock bag and store in the freezer.  When ready to eat, thaw only the amount of saag you want to eat and mix it with fresh tadka made in ghee. Serve hot!