I freeze celery all the time. I chop it up for my soups, lay them single file on a cookie sheet and put them into the freezer until frozen. Then I place them in a freezer bag for later use. Laying them on a cookie sheet without covering keeps them from freezing together so when you go to use them, they're not all in alump together. I do this with onions, carrots, celery, peppers and squash. I also freeze leftover milk too. Don't like to waste anything if I can help it. When I picked up some eggnog the other day, they had a slip of paper to give me and it stated right there you could freeze it.