On Thanksgiving I went to mass. The Priest bless bread and wine to take home. What should I do with the left over wine? I was going to pour it outside on the grass.
Pious custom has been to either burn or bury blessed objects that can no longer be used. Pouring blessed wine into the ground would be in keeping with this pious tradition.
I would not, however, say that this is an absolute rule. Wine that has been blessed has been blessed for its use. Once the wine turns bad it is no longer usable and thus one could argue that it can simply be poured down a regular drain.