If you only need a handful of onions or celery for certain dishes, it makes sense to freeze them. That way, you can have them on hand to use without worrying about them going bad in your refrigerator. Freeze them in small batches of individual portions for the ultimate in convenience. You can also freeze a mixture of onions and celery if you generally use them together.
Wash the celery in cool water. Choose crisp stalks with few strings for freezing because limp or tough celery doesn't freeze well.
Cut the celery into 1/2-inch or longer pieces. Cut them to the size you would normally use for your recipes.
Bring a large pot of water to a full boil.
Drop the celery pieces in the boiling water, adding no more than 1/2 pound of celery at a time.
Boil the celery for 3 minutes. Remove the celery from the water with a slotted spoon and place it in a bowl of ice water to stop the cooking process.
Drain the celery in a colander. Pat the celery surface dry with a clean paper towel.
Measure out portions of the prepared celery. Wrap the portions in freezer wrap. Place the wrapped packages in a freezer storage bag and remove as much air as possible by pressing down on the bag while sealing. Freeze immediately.
Rinse the onions in cool water. Peel the outer skin off the bulb.
Cut the onions into pieces for the recipes you use. Both diced onions and rings freeze well.
Place portions into small freezer bags. Press the air out of the bags and seal them closed.
Lay the bags in the freezer. Laying the bags flat speeds freezing.