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Home » Key Stage 2 Science » Transpiration Experiment – Colour Changing Flowers

Transpiration Experiment – Colour Changing Flowers

Modified: Mar 25, 2025 · Published: May 7, 2024 by Emma Vanstone · This post may contain affiliate links · 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

white carnations with coloured petals. The colour of the petals has changed because food colouring has travelled up the

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.

Water

Small jar or vase

white flower with the petals coloured red as part of a transpiration experiment

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.

carnation coloured using food colouring to demonstrate transpiration. Easy plant science for kids

Free Transpiration Experiment Instructions

Colour Changing Flowers Instruction Sheet
Instructions for a colourful flower transpiration experiment. White flowers change colour when placed in a mixture of food colouring and water.

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 of water and the other in a different colour. After a few hours, you should have a flower with two different-coloured petals!

Multicoloured flower - transpiration experiment for kids

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. Thus, there is a constant transpiration stream 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.

transpiration diagram showing water being transported up a plant from root to leaves

What affects the speed of transpiration?

The rate of transpiration is affected by environmental factors

Factors affecting transpiration

Light

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.

  • mini DIY greenhouse made from a plastic bottle
    Easy DIY Mini Greenhouses
  • labelled flower diagram made with a dissected flower
    Dissect a Flower – STEM Challenge
  • Spring Science Experiments
    20 Spring Science Experiments for Kids
  • Sticky Seeds – a seed dispersal investigation
Colour Changing Flowers -  easy transpiration experiment for kids. Colourful plant science experiment for kids #plantscience #scienceforkids #transpiration Transpiration for kids
Transpiration Experiment for Kids

Contains Affiliate Links

Different white flowers with brightly coloured petals after being left in food colouring and water for a transpiration demonstration.

Last Updated on March 25, 2025 by Emma Vanstone

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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

Comments

  1. Melissa

    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!

    Reply
    • ScienceSparks

      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!

      Reply
  2. Janae

    September 28, 2011 at 8:50 am

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

    Reply
    • ScienceSparks

      September 29, 2011 at 6:12 pm

      It is great! x

      Reply
  3. maggy, red ted art

    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!

    Maggy

    Reply
    • ScienceSparks

      September 29, 2011 at 6:12 pm

      Thanks Maggy

      Reply
  4. mum of all trades

    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!

    Reply
    • ScienceSparks

      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! 🙂

      Reply
  5. mummiafelice

    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

    Reply
    • ScienceSparks

      October 12, 2011 at 9:19 pm

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

      Reply
  6. Fiona @Coombemill

    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.

    Reply
    • ScienceSparks

      October 12, 2011 at 9:18 pm

      Thank you lovely! x

      Reply
  7. Rainy Day Mum

    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.

    Reply
    • ScienceSparks

      October 04, 2011 at 12:33 pm

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

      Reply
  8. creativejewishmom/sara

    October 06, 2011 at 8:42 pm

    thanks so much for sharing on Craft Schooling Sunday!

    Reply
  9. ScienceSparks

    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! 🙂

    Reply
  10. ScienceSparks

    October 12, 2011 at 9:17 pm

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

    Reply
  11. Mama Pea Pod

    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!

    Reply
    • ScienceSparks

      January 02, 2012 at 7:55 pm

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

      Reply
  12. Kathy

    January 09, 2012 at 9:39 pm

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

    Reply
    • ScienceSparks

      January 09, 2012 at 10:54 pm

      Usually by the end of the day!

      Reply
  13. Christy

    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?

    Reply
  14. Sonia

    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.

    Reply
    • ScienceSparks

      November 05, 2012 at 8:39 am

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

      Reply
  15. Pinkoddy

    January 30, 2014 at 9:23 pm

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

    Reply
  16. Sthuthukile Ngcobo

    April 17, 2018 at 9:56 am

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

    Reply

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