Color Changing Carnations

Where does the water go when a plant is watered?

Where does the water go when a plant is watered? With this experiment, children can discover for themselves how essential the functions of roots and stems are to plant growth. As the colored water is absorbed, students will be able to see how the water is absorbed into the plant and will be amazed when the petals of the carnation change color.

Experiment Materials

  • 6 white carnations
  • 8 plastic cups
  • Food coloring (red, blue, and green)
  • Knife (you'll need an adult helper for this)
  • Water


  1. Fill four of the cups one-half full with water.
  2. Add about 20-30 drops of food coloring to three of the cups of water (red, blue, and green). In this case, more food coloring is better! The fourth cup should contain just plain water.
  3. Before placing any of the flowers in the cups of water, have an adult trim the stem of each flower at an angle to create a fresh cut. For cut flowers, it is important for the stem tubes to be filled with water. If air gets in the tube no water can move up the stem. Many gardeners and florists cut stems under water so no air bubbles can get in to break the tube of water and make the flower wilt.
  4. Place one freshly cut white carnation in the cup containing the uncolored water. Then place a freshly cut white carnation in each of the three cups of colored water. Save the remaining two carnations for the next step. As you wait to see the results, make some predictions: How will the carnation in the plain water compare to the carnations in the colored water? Which color will be soaked up first? How long will it take? Will one of the colors create a deeper colored flower or do the colors all absorb to the same degree?
  5. The next step is a popular trick called “Split Ends,” and it requires some help from an adult. Have your adult helper use a sharp knife to slit the stem straight down the middle. Put each half of the stem into a cup of different colored water (try positioning the red and blue cups next to each other, for example). Make a few more predictions: Which color will be soaked up? Will the colors mix to make a new color or will the color of the flower be divided down the middle? Just remember to keep the ends of the stems wet at all times and to make fresh cuts on the ends.
  6. You’ll want to check back every few hours to see how things are progressing. It may take as long as 24 hours for the colored water to work its way up to the white petals. At the conclusion of your experiment, remember to examine the whole plant carefully including the stems, leaves, buds, and petals to find every trace of color.

How Does It Work?

As you probably noticed, most plants have a “drinking” problem. Okay, in this case it’s a good problem. Most plants “drink” water from the ground through their roots. The water travels up the stem of the plant into the leaves and flowers where it makes food. When a flower is cut, it no longer has its roots, but the stem of the flower still “drinks” up the water and provides it to the leaves and flowers.

Okay, now it’s time to get technical. There are two things that combine to move water through plants — transpiration and cohesion. Water evaporating from the leaves, buds, and petals (transpiration) pulls water up the stem of the plant. This works in the same way as sucking on a straw. Water that evaporates from the leaves “pulls” other water behind it up to fill the space left by the evaporating water, but instead of your mouth providing the suction (as with a straw) the movement is due to evaporating water. This can happen because water sticks to itself (called water cohesion) and because the tubes in the plant stem are very small (in a part of the plant called the xylem). This process is called capillary action.

Coloring the water with food coloring does not harm the plant in any way, but it allows you to see the movement of water through the roots to the shoots. Splitting the stem simply proves that the tiny tubes in the stem run all the way from the stem to the petals of the flowers. Our unofficial tests indicated that the blue dye went up the carnations the fastest, followed by the red dye and then the green dye.

Like colored dyes in this experiment, some chemicals that pollute our waters can get into the soil and ground water and contaminate our vegetables and plants growing in the soil. Some chemicals and pollutants, just like the color dyes, may travel up into the plant and affect its health or growth.

Science Fair Connection

Color Changing Carnations is a good science fair experiment because you start with a control, or something that doesn’t change in the experiment (in this case, the control is the carnation in the plain water). Then you add a variable, or change something in the experiment (in this case, you change the color of the liquid) and you make some comparisons between the control flower and the flower that has been exposed to the variable. You think of another idea to test, like splitting the stem in half and testing two colors at once, and you make some more comparisons.

So, if you wanted to make Color Changing Carnations your own science fair project, what other questions could you ask?

  • What would happen if you split the carnation and put one side of it in water and the other side in colored water? Would the flower be all one color or would only half of it absorb the color?
  • What would happen if you changed the way you colored the liquid? Try adding a colored drink powder like KoolAid, Gatorade, or lemonade instead of using food coloring. Does the manner in which you color the water make a difference?
  • What would happen if you put the carnation stem into soda instead of water? Could you create a root beer colored carnation? What if you used clear colored soda for one side of the flower and dark colored soda for the other side? Would the flower be divided in color, all one color, or not colored at all?
  • If you take the carnation out of the cups, do both sides of the flower dry up at the same rate? What happens to the colored side? Does the color disappear as it dries up?
  • What if you put one carnation in regular water and one carnation in water mixed with Miracle Gro fertilizer? Would it have any impact on the flower? Why or why not?
  • What if you put one side of the flower in water and one side in salt water? Would the flower thrive or would one side thrive and the other side shrivel up and die?

Let your imagination run wild! There are all kinds of questions about carnations that you could explore for a science fair project. Just remember to change only one variable at a time. Compare the effect of that variable to the flower with no variable added (the control), document your discoveries, and come to some conclusions about plants and how they absorb liquids. Prepare your presentation and get ready to share your research with everyone who attends the science fair.