One of my all-time favorite science experiment growing up was taking a white carnation and putting it in colored water and watching the carnation change color through capillary action.
I loved everything about this experiment – turning an ordinary white flower into a beautiful green flower, the waiting time – yes it can be fun to keep checking it every few hours eagerly awaiting a change, and the satisfying finish of the colored flower and understanding how plants absorb water to survive.
I’ve been wanting to do this experiment with my kids for awhile now, but was waiting until I thought they might be old enough to 1) have the patience to wait for the flower to change color and 2) not want to play with the water and flower too much that they would spill or ruin the experiment.
When my kids couldn’t stop admiring the flowers they gave me for Mother’s Day, I decided it was time to do this experiment! I knew they would especially love watching the flowers change colors, but we’re also adding in a few more plants.
We’re doing the coloring changing plants experiment with 4 different plants (carnations, roses, celery, and Chinese cabbage leaves) to see the differences, similarities, and compare the results.
Let’s talk about water absorption in plants
Plants “drink” water from their roots. When the plants are cut (like in this experiment), they can “drink” the water through their stem. Water is transported through a plant by the xylem. The main purpose of the xylem is to transport water and nutrients from the plant’s roots to its stem, leaves, and flower (if present).
Plants seem to defy gravity by moving the water upward from the roots to flowers, this is called capillary action. Transpiration (the evaporation of water from the surface of the plant) creates negative pressure at the top of the plant. This negative pressure causes the xylem to pull water from the roots and soil.
Several other forces help make the capillary action possible. These are adhesion between water the the xylem plant molecules, and cohesion which is the attraction of water molecules to each other.
All these forces combine to pull the water from the roots and disperse it throughout the entire plant, all the way to the leaves and flowers. This is why we see the colored water change the color of the stems, leaves, and petals of our plants in this experiment.
Color Changing Plants Experiment
This experiment is a fun and colorful way to introduce kids to how plants absorb water. Preschoolers aged 3+ will be able to participate in the experiment and toddlers aged 1-2 will enjoy observing the experiment.
We tested four different types of plants: white carnations, white roses, Chinese cabbage, and celery. We wanted to see which ones absorbed the color best and also which colored the most quickly.
This experiment involves food coloring. This may stain so I recommend doing this experiment on a protected or covered surface, and with your children wearing clothes that are ok to get stains.
I recommend the parents do the trimming the plants before placing them in the water. You will be using sharp knives or scissors, and most children will not be able to do this step safely on their own.
- Glass jars or cups
- Food coloring
- Sharp kitchen knife (optional)
- White or very light colored plants for the experiment, we used:
white carnations, white roses, Chinese cabbage, and celery (daisies would also work well, but will take ~2-7 days to fully saturate with color)
- Parents do this step: Prepare your plants for the experiment by trimming at least an inch off the ends of the plants (we found the shorter the stem, the quicker they absorbed the color and the more vibrant the color)
1A. Optional: For the roses, carefully slice the stem in half or in three parts. This will allow you to change the flower to multiple colors.
2. Fill the glass jars or cups with water
3. Add at least 10 drops of food coloring to each glass jar or cup
4. Stir the food coloring and water to make sure it is well dispersed
5. Place one or two plants into each glass jar or cup
6. Ask your child to make a hypothesis about what will happen to the plant
7. Observe the results after 1 hour, 3 hours, 1 day, 2 days, and up to a week for the flowers (but change the water out every 2-3 days)
8. Ask your child if the result is what they expected or not, then explain what happened (see explaination below)
The plant absorbed the colored water through a process called capillary action. Normally plants absorb water through their roots, but since we are using cut plants, they are absorbing it through their stems. The water is drawn in the xylem through capillary action and is dispersed through out the entire plant from stem to tips of the leaves and petals.
When the water is colored, the color from the water can stain the plant, especially if it is a light colored plant, such as the white petals on our flowers.
The carnations took around 5 days to fully saturate with color (as seen in the final picture above). They took 1 day to show faint coloring, and the color continued to saturate more and more as the days progressed. We also observed that the carnations with the shortest stems absorbed the most color into their petals.
The roses showed color within hours, and after one day had already reached their full saturation (as shown above). This would be a good flower to use if your kids want to see instant gratification with this experiment. However, it is also the most expensive flower…
The Chinese cabbage started to show coloring within hours, and were fully saturated in 2 days. The blue and red colored leaves showed up best, while the yellow and green coloring were not as obvious because they were so similar to the natural color of the cabbage.
The celery started to show color overnight and were fully saturated in 2 days. I used the darker celery stalks (because they had more leaves), but I think the color would have showed up better on the lighter colored inner stalks. Similar to the cabbage, the red and blue showed up best, while the yellow and green were hard to see because it was so close to the original color fo the celery.
My kids and I all loved this experiment! My kids excitedly ran to check on the plants every time they entered our kitchen. They would enthusiastically tell me what was happening to the plants and how cool it was.
My favorite part was when, a few days after we started the experiment, my mother-in-law came to visit. Before she came in the house my son told her, “I can’t wait for you to see our science experiments. We have plants all over the kitchen counter because we are doing science.”
Kids are never too young to instill a passion for learning and science. Start them young, introduce STEAM concepts often, and you will be surprised at how quickly your kids learn and love doing these activities.
Have you tried this experiment with your kids yet? Which plant did you use?