Simple Science Experiments: Coloring Flowers from the Inside Out

What color of flowers do you like? You can turn flowers that color from the inside out! This month’s simple science experiment will tinker with the inner workings of flowers and celery, too. Now, we all know that plants don’t have a heart to pump their fluids up from the ground to their leaves, so how exactly does this happen?

The process at work here is “capillary action.” Plants have tiny little tubules going up their stems. Think about eating a piece of celery ─ those “strings” that get caught in your teeth are what I’m talking about. Water is naturally attracted to these tubes through “adhesion” and gets pulled upward. The smaller a tube is the higher water will get pulled up. This is how even the mightiest trees bring water up from their roots to the tallest of their branches. How can we test this? I’m glad you asked…

Materials

• White carnations and/or bulb of leafy celery
• Two vases (or two tall drinking glasses)
• Water
• Food coloring
• Sharp knife (Parental assistance is recommended for use).

Procedure for multi-colored experiment

• Fill two vases (or drinking glasses) with tap water. Add enough food coloring to each until water turns a dark hue. Use different colors in each vase.
• Carefully cut the white carnation down to about 18 inches. With a careful cut, slice the stem vertically from the bottom until just below the flower. If the cut is not even, don’t worry. The results are interesting. (If using celery, do the same cut, but don’t go quite as near the top, as it may split.)
• Put the two ends of the carnation stem (or celery) into the two different glasses of colored water.
• Wait a few hours and make your observations.
• Experiment further: If you didn’t already do the experiment with the celery, try it out. The effects are similar but not exactly the same.

Procedure for a single color experiment 

• This version is a little easier to do if you don’t want to use a knife. Put a few drops of your chosen color into a glass.
• Snip the end of the floral stem to allow for good water motion.
• Put the flower (or celery) in the vase and wait for results!

You will notice that the food coloring makes its way up the stem and into the white flower petal, first coloring the edges and then making its way inward. Not only that, but the carnation is two different colors now, due to the water being brought up the tubes on different sides of the stem. The food coloring gets pulled up along with the water through a process called “diffusion.” This means that the food coloring wants to move from a place where there is a lot of it (in the glass), to a place where there is little (in the flower). The process is similar to when you spray air freshener in a room ─ the spray moves from where it started and disperses all throughout the room.

Let the carnations stay in the water for several days to get a good coloring. The celery is interesting too, because when you take it out of the water, you can see the tubes completely saturated with the color apart from the rest of the plant material. Experiment further: Will different colors work the same way? Would a red carnation turn purple if you dunked it in blue food coloring? What if you made purple food coloring with red and blue dye and then put the carnation in it? Do other flowers do the same thing? Ask your questions, and discover the answers.

Steve Davala is a middle school science teacher who likes to write. He’s has two kids and subjects them to these science activities as guinea pigs. Follow him on Twitter or email your science questions to steve.davala@gmail.com.