Summarize this article:

Place a large stock pot on your stove, and fill it with enough water to cover all of the celery that you're freezing. Turn the burner to high, and allow the pot to come to a full boil.  When it comes to deciding how much water to add to the pot, using 1 gallon (3.8 L) for every pound (454 g) of celery is a good rule of thumb. If you don't plan to keep the celery in your freezer for more than two months, you don't necessarily have to blanch it before freezing. It will help preserve the flavor more effectively, though, so you may want to do even if you plan to use it within 8 weeks. for several minutes. Once the water is boiling, place the chopped celery in the pot. Give the water a good stir after adding the celery to ensure that it's all submerged. Let the celery cook in the boiling water for 3 minutes.  Placing the celery in a boiler basket before adding it to the water makes it much easier to add it to and remove it from the water. Set a timer when you place the celery in the water so you're sure not to overcook it. When the celery has cooked for 3 minutes, take it out of the boiling water. Immediately, transfer it to a large bowl of ice water to stop the cooking process. Let it sit in the cold water for about 3 minutes. If you don't want to create an ice water bath for the celery, you can place it in a colander and set it under cold running water to cool it as quickly as possible.

Summary:
Boil a large pot of water. Cook the celery Remove the celery from the boiling water and transfer it to cold water.