There are two ways which have worked for me:
1) Take the plant, wrap it in a paper towel lightly sprinkled with tank water, place in ziplock bag, place in box with newspaper to cushion the bag.
2) Take the plant, place it in an aquarium bag with no additional water in it, fill it with air, tie it up tightly with a rubber band, and place it in a box with newspaper to act as a cushion.
I find that heat is more troublesome for shipping than cold.
Carlos |