osmosis flower experiment

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How to Make Colored Flowers Using Science

It’s easy to make colored flowers using a simple science project. The project is safe and easy enough that kids can try it. You get beautiful colored flowers while applying several scientific concepts, including osmosis, capillary action , cohesion , transpiration, and the function of xylem in plants.

How to Make Colored Flowers the Easy Way

All you really need for making a colored flower is a flower and some colored water. But, some flowers work better than others. The chemical you choose as a dye also matters. Ideally, use white or pale freshly-cut flowers. Carnations and daisy work best. Flowers from woody plants, like roses, also work but take longer to change colors. The healthier the flowers are, the better they’ll pick up the color. Ordinary food coloring works great as a dye because it is water-based. Avoid oil-based dyes because they’ll just float on the water surface so the flower won’t absorb them.

• Fresh flowers
• Glass, vase, or cup
• Trim the stems of the cut flowers at a 45° angle. Ideally, make the cut underwater so you don’t get air bubbles on the cut end of the stem that block water absorption. The fresh, angled cut helps the flowers absorb water and keeps the stem from sitting flat on the floor of the glass.
• Add warm water to the glass. The warm temperature helps color the flowers more quickly. Add a splash of vinegar and spoonful of sugar. If you want exact measurements, use 1 teaspoon of vinegar and 1 teaspoon of sugar for each 200 milliliters of warm water. Technically, you don’t need the vinegar or sugar, but they help keep the flowers healthy. Vinegar is a natural antimicrobial agent that also makes the water more acidic, while sugar gives the flower nutrients.
• Add food coloring to the glass. You need quite a bit of dye (probably 25-30 drops) because the flower does not absorb all of the water.
• Place the flower in the colored water. The edges of the petals pick up color within a few hours. It may take a full day to completely color the flower.

How to Make Two-Colored Flowers

Now that you understand the basic technique, try using two dyes.

• Trim the flower stems with an angled cut. This time, carefully split the stem from the cut end up toward the flower.
• Add warm water, sugar, and vinegar to two glasses. Choose short, narrow glasses so you won’t have to separate the split stem too much.
• Add one color of food coloring to one glass and a second color to the other glass. Keep in mind the colors will blend a bit where they meet in the petals. For example, if you use blue food coloring and yellow food coloring, you might see some green petals.
• Carefully open the split on the stem so one half is in one glass while the other half is in the other glass.

How to Make Tie Dye and Rainbow Flowers

Splitting the stem into even more sections gives the flowers a tie dye or rainbow effect. This is one of the methods of making rainbow roses .

The Science Behind Colored Flowers

Plants drink water through a process called transpiration. Water evaporates from the petals, leaves, and stems of the flowers. Most of the water leaves through tiny openings in the leaves and stems called stomata. Water molecules stick to another another through cohesion. Basically, hydrogen bonds between water molecules attract them to each other. So, when water exits through stomata, it pulls more water up the stem.

Water and dissolved nutrients (and dye) move through the xylem in the stem. The xylem is not a long open tube, like a straw. Instead, it consists of stacks of tubes connected by narrow openings. These pores make the xylem semipermeable. Small molecules move through the xylem, but large ones don’t. So, the movement of water up the xylem is by osmosis rather than simple diffusion . Capillary action involves the cohesion of water molecules and adhesion of water to the xylem wall also plays a role. Water rises up in the xylem above ground level because the small diameter of the xylem bundles. But, the positive pressure of nutrients from the roots (or dissolved sugar in the glass) and the negative pressure of transpiration are essential for getting water all the way to the tips of the flower petals.

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Transpiration Experiment – Colour Changing Flowers

May 7, 2024 By Emma Vanstone 26 Comments

Do you know you can change the colour of white flowers by placing them in a pot of food colouring and water? This easy colour-changing flower science experiment is great for learning about transpiration and transport in plants .

Easy Transpiration Experiment

How to make colour-changing flowers

You’ll need.

White flowers

Food colouring – we’ve found Wilton gel colours work well. Natural food colourings DO NOT work in our experience.

Small jar or vase

Transpiration experiment – instructions

Trim the flowers at the stalks.

Fill a vase or jar with water and add a little food colouring.

Place the flowers in the jar and leave for a few hours.

Usually, you will see the flowers change colour within a few hours.

Extra Transpiration Challenges

Try carefully splitting a stem in half with a sharp knife ( ask an adult to do this )

Place one half of the stem in one colour water and the other in a different colour. After a few hours, you should have a flower two different coloured petals!

What is Transpiration?

The white petals change colour because of something called the transpiration stream . Transpiration is the movement of water up the stem of a plant from root to leaf when water is lost from the plant due to evaporation and diffusion of water from a plant’s surface. Firstly, water is absorbed by the root and moves through root hair cells via the process of osmosis . It then moves into the xylem vessel, which is the tube that carries the water up the stem. Water moves up the xylem vessel by adhesion (being attracted to the side of the vessel) and cohesion (water molecules being attracted to each other).

When water evaporates from the surface of the leaves, the pressure change pulls the column of water upwards to replace the water lost. There’s a constant transpiration stream of water through the plant.

The best way to consider this is to imagine you have a thick milkshake – the straw can’t carry the milkshake up itself, but if you suck from the top, the milkshake is sucked up the straw. It moves in a column because water molecules are attracted to each other.

What affects the speed of transpiration?

The rate of transpiration is affected by environmental factors

Factors affecting transpiration

Transpiration is faster when there’s more sunlight. Stomata ( tiny pores on the surface of a plant ) close when it’s dark as they don’t need to be open when photosynthesis is not happening. Photosynthesis also needs sunlight. When the stomata are closed, water cannot escape from the plant’s surface.

Temperature

Transpiration happens at a faster rate in higher temperatures. In warm weather, water particles evaporate and diffuse through the stomata faster, increasing the transpiration rate.

Air movement around the plant

When airflow around a plant is good, transpiration is faster as the water vapour that has just diffused and evaporated from the leaf is moved away, increasing the concentration gradient between the air and the inside of the leaf. Diffusion is faster when the concentration gradient is more significant.

The effect of increasing airflow on the rate of transpiration can be demonstrated using celery, food colouring, water and a hair dryer!

What food colouring should I use?

We have found that natural food colours don’t work, but these Wilton gel colours work every time.

If you liked this experiment, don’t forget to try my other plant science experiments .

Contains Affiliate Links

Last Updated on September 17, 2024 by Emma Vanstone

Safety Notice

Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

Reader Interactions

September 26, 2011 at 8:55 pm

I did this for my kids this summer. We used daisy’s…it didn’t work. I have done it with carnations before and it worked, but not sure why daisy’s didn’t work!

October 12, 2011 at 9:13 pm

I think the stem structure can vary somewhat and only certain flowers work effectively. Definitely try carnations next time!

September 28, 2011 at 8:50 am

Thanks for the tip! I’m going to try this one out!

September 29, 2011 at 6:12 pm

It is great! x

September 28, 2011 at 1:32 pm

Yet another fabulous experiment to explore with children! I remember always wanting to try this but never getting round to it.. I WILL with my kids! 😉

Thank you for liking to Kids Get Crafty!

Thanks Maggy

September 30, 2011 at 9:47 pm

You have so many great ideas on your blog. I would love if you would link some of them up to my Weekend Wonders blog hop!

October 12, 2011 at 9:18 pm

Is that a Sat or a Sunday? Can you send us the link, as that would be great! Thanks for stopping by, we are so pleased you like it! 🙂

October 01, 2011 at 6:52 am

I don’t know of a child that doesn’t find this utterly fascinating! It’s such a great idea! I have to have a go at this with Little One!

Thank you for linking up to #handmadethursday x

October 12, 2011 at 9:19 pm

Thank you kindly! Let us know if you do have a go! 🙂 x

October 03, 2011 at 9:43 pm

What a great experiment! Will definitely be giving this one a go! Well done girls, another simple but fun experiement my children will love.

Thank you lovely! x

October 04, 2011 at 11:02 am

I love this experiment – it works really well in the spring as well with Daffodiles we always used to have multi coloured daffs in the house in spring.

October 04, 2011 at 12:33 pm

Thank you! We will definitely have a go with daffodils in the spring.

October 06, 2011 at 8:42 pm

thanks so much for sharing on Craft Schooling Sunday!

October 12, 2011 at 9:12 pm

Thank you so much. We will stop by. If you have craft posts yourself come and link to our fun sparks on a Thursday! 🙂

October 12, 2011 at 9:17 pm

We are all linked up so thank you! A beautiful sea or turquoise if ever I saw!

January 02, 2012 at 4:44 pm

I remember doing these as a kid with my grandmother – so fun! Thanks for reminding me to do them with my own kids!

January 02, 2012 at 7:55 pm

oh wow! Thats great. It is a really fab experiment! x

January 09, 2012 at 9:39 pm

How long does it take for you to see the change in color?

January 09, 2012 at 10:54 pm

Usually by the end of the day!

March 12, 2012 at 6:28 am

Wondering…If I dye 6 carnations, seperately, a different color each (like the colors of the rainbow), could I then combine them in one vase of plain water after the petals have changed color?

November 05, 2012 at 1:03 am

Hi I tried this but it didn’t work I used a white flower or should I wait longer.

November 05, 2012 at 8:39 am

Make wait longer, or make your coloured solution stronger. Good luck.

January 30, 2014 at 9:23 pm

This is really interesting – am sure my boys would really love this.

April 17, 2018 at 9:56 am

It is a very colourful science topic and also interesting to play around with it

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How to Tie Dye Flowers With Osmosis

Introduction: How to Tie Dye Flowers With Osmosis

It may seem like magic, but by leveraging the very building blocks of plant biology, you can easily make your very own beautiful rainbow colored tie dye flowers. This is such a fun project to do with the family or with kids and it's a surprising amount of fun to check in every hour to see all the color changes that happen.

• However many fresh white flowers you would like (we recommend roses and lilies from your local grocery store)
• A set of food-safe food coloring
• Several glass cups, jars, containers, etc. (glass so you can see your colors, but not required)
• Cutting board and thin cutting knife
• A pitcher of water

Step 1: Prepare Materials

• Dry the stems of the flowers you have selected for dyeing[Optional] Leave the flowers out of water for 30-60 minutes before the experiment so that they are particularly thirsty. This step will slightly reduce the time they need to sit in the water.
• Cut the stems of your flowers to the desired height, and keeping in mind that they will need to be able to comfortably sit in the water containers you have selected. If you have shorter containers, you may need to cut your flower stems shorter.
• Separate out your flowers between single color, two color, three color, and four color. Then for each set of flowers past single color carefully split the stems into corresponding halves, thirds, or fourths. Use as thin a knife as possible, and do your best to evenly split the stem without scraping the xylem inside.

Step 2: Prepare Food Coloring and Setup

• Fill your glass containers with the different colors. Be generous with how much food coloring you put into the water so that you get deeper colors to show on the petals; in fact don't be shy about dumping all your food coloring into each container. You can mix colors (i.e. red+yellow=orange) which should work well. If you split a stem and put half in red and half in yellow you will also see some orange emerging amidst the clearly yellow and red, but not as much as if you had mixed the orange ahead of time.
• Now place the stems of all your colors into the different colored containers as you'd like to see them colored. We prefer a nice mix of everything.

Step 3: Sit and Wait!

• Now you wait. Some color should start emerging after the first hour, and after 24 hours you probably will have considerable color effects. We stopped after 24 hours as we loved the tie-dye effect it produced, but you can leave the flowers in longer and see what happens.
• Place your tie-dyed flowers in a vase of fresh water (no food coloring), add some flower food mix if the store gave you any, and enjoy them as long as they last. Our tie dye flowers survived just as long as some plain white flowers that we used as a control group, and we do not believe that the dye has any effect on their lifespan.

Step 4: The Science of It All

Normally flowers will pull water from their roots all the way up to their leaves and petals where they use it to make food through photosynthesis. Flowers with their roots cut will still be able to absorb water through xylem which is a system of tine hollow tubes that behave similarly to a bundle of straws sucking the water upwards. So the water with the food coloring is able to travel up to the petals via the xylem. Once the water arrives in the petals, it proceeds to evaporate out of microscopic holes in the plant in a process called transpiration. The food dye is not able to evaporate along with the water, so instead it is left behind in the petals which results in the beautiful coloring. This is a fun experiment to learn about plant structures, but more critical to understand is that by using this same process harmful chemicals and pollutants can contaminate the vegetables we eat or the plants we live with.

In florist terms the method is called the absorption method, and the dye results can be controlled by monitoring the time the flower spends in the water; generally the longer time the flower spends in the colored water, the deeper the shade will turn.

Step 5: What to Do If Your Flowers Don't Change Color?

• Some flowers as you can see in the video just aren't as conducive to picking up the colors as others. This can often be due to the flowers having herbaceous vs. woody stem types. We learned that roses and lilies are almost always a safe bet. Lilies were definitely our favorite.
• Give them some more time, we gave our flowers nearly 24 hours to get the coloring in the photos. Oftentimes if you accidentally chose woody stem types it can take them multiple days to show color.
• Did you use enough food coloring? Try dumping in the whole bottle. More is always better (depending on what color you're looking for).If all else fails, take to the following infamous back-up plan pictured above.

We hope you enjoyed this how to tutorial for how tie dye flowers using osmosis. Share this post with your friends and comment below with thoughts or ideas. Learn more about us http://www.craft-curious.com/

• 1 white flower (a carnation, daffodil, rose, tulip or chrysanthemum works well)
• 1 cutting board
• 1 sharp knife
• 2 drinking glasses
• Food coloring of two different colors

Short explanation

Long explanation.

• Which flower species gives the best result?
• What does the flower look like after 1, 2, 4, 6, 12, 24, 48, 72 hours?
• How many parts can you divide the stem into and still make the demonstration work?
• What happens if you place the stem in some other kind of colored liquid (soda, juice, coffee)?
• Is there any color that the flower has a harder time turning into?
• What kind of color (watercolor, oil paint, etc.) gives the best results?
• What happens if you place one half of the stem in water with plant nutrients?
• What happens if you place one half of the stem in salt water?

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Colour Changing Flowers Science Experiment - A fun science project for kids

MORE FUN SCIENCE PROJECTS FOR KIDS

Colour changing flowers science experiement for preschoolers.

Supplies needed for the colour changing flowers science experiment

• White flowers
• Glass jars (we used baby food jars)
• Liquid water colour or food colouring

What are the best flowers to use for the colour changing flower experiment?

How to set up the colour changing flowers experiment 

Step 1: get your supplies ready for the flower experiment and predict what will happen.

STEP 2: Fill glass jars with coloured water

STEP 3: Prepare the flowers

Step 4: place the flowers into the coloured water .

How long does it take to change the colour of a flower with food colouring or liquid watercolour?

The science behind the colour changing flowers science experiment. 

Cool Science Experiments for Preschoolers (and older kids too!)

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Color Changing Flowers

It’s easy to see how plants drink water by doing this simple science experiment: Color Changing Flowers. Learn about plant biology and create a beautiful flower rainbow the kids will love. It’s a must-try kids’ plant experiment!

And for endless science fun, check out our 30 Science Experiments in our shop!

Getting Ready

This experiment can be done with any white flower. Carnations, daisies and white roses will all yield gorgeous results.

We live next to a field with hundreds of wild white daisies growing in it. One sunny day we took a walk and picked a handful.

Once we got home we filled six small film canisters with water and then dripped about 3 drops of food coloring in each one. We made an entire rainbow: red, orange, yellow, green, blue and purple. The kids placed a few flowers in each container and then we waited to see what would happen.

Color Changing Daisies

It took a few hours for anything visual to happen. During that time, we talked about how plants drink water.

I asked the kids how very tall plants get water all the way up to their highest leaves, branches and flowers. The kids had lots of very funny and creative ideas!

I guided the discussion to lead my children to the conclusion that plants absorb water through their roots in the ground. Water moves from the roots up through the stem and into the leaves and flowers through tissue called xylem.

After a couple of hours we started to see blue-tinged petals on the flower in the blue water. Little by little, each of the other flowers changed colors, too! It was interesting to note that some of the colors, like blue and purple, were more vibrant than other colors, like orange and yellow.

We left our color changing daisies overnight to develop. The next morning we had a beautiful daisy rainbow.

How Plants Drink Water

As mentioned above, water moves through plants through the xylem . But how does water defy gravity and move upward to the very highest leaves of a tree?

The answer lies in capillary action , which is defined as the process that plants use to pull water up from the ground. There are several factors that enable capillary action to happen.

First is the force of adhesion, which is the attraction between water molecules and plant fibers.

Second is the force of cohesion, which is the attraction of one water molecule to another water molecule.

Third is transpiration. When water evaporates from the leaves, buds, and petals of a plant, more water is drawn upward to fill in the empty space. It is similar to what happens when a person sucks water through a straw.

All three of these factors combine to enable a plant to draw water from the ground and distribute it throughout the entire plant. Doing this color changing flower experiment makes it easy to see how capillary action works.

Must-Try Science Activities

Continue the science fun with our 30 Science Experiments – complete with a no prep journal!

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