Here is how it's done.
Begin with the following key items for this experiment.
Add 10 drops of food colouring to each of the cups then add 1/4 of a cup to each cup. Mix.
Place one stalk of celery into each of the cups.
You'll notice that the colouring begins to draw up the celery almost immediately.
I placed each cup in a container to hold them still and fastened each cup together using sticky tape.
Waiting, waiting, waiting.
Possum gets to enjoy some left over celery.
The celery leaves have changed colour because of the water. This is after 12 hours.