Harvest the wheat grass when the blades start to folk. Gather a bunch of blades in your hand. Cut the blades a few centimeters above the soil with sharp, clean scissors. Cut as much grass as needed for storage.
Place a handful of blades into each freezer bag. Remove as much air from each bag as possible by gently pressing it out of the bag with your hands. Close the bags tightly.
Put on goggles and heavy gloves. Set ¼ lb. of dry ice into a 5-gallon bucket. Pick the dry ice up with tongs and set it in the bottom of the bucket.
Lay the freezer bags of wheat grass on top of the dry ice. Set the lid on top of the bucket loosely to allow air to escape. Press the lid down tightly after six hours.
Open the lid daily to check on the dry ice. When the dry ice has vanished, remove the bags of grass. Set the bags in your freezer until needed.