Colour Changing Flowers – Transpiration!

So you have some white flowers but actually wouldn’t they look good with a bit of red in them? Or maybe blue? Not only are they pretty but can be used to demonstrate transpiration.

Coloured carnation

How could you do this? Well with what looks like a little bit of magic and a huge dollop of science!

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


Trim the flowers at the stalks.

Fill as vase or jar with water and add some food colouring of your choice.

Put your flowers in the water and wait.

Usually you can see effects within a few hours!

coloured carnation

This one is yellow and black.

Extra Challenge

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 with different coloured petals!

Multicoloured flower


What is Transpiration

The reason this happens is because of something called the transpiration stream. This 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 occurring at the leaves. Firstly water is absorbed by the root and moves through root hair cells via the process of osmosis (we will look at this another day!). It then moves into the xylem vessel which is the tube that carries the water up the plant. Plants are not like us with pumping mechanism that pushes our blood around, so water moves up the vessel by adhesion (being attracted to the side of the vessel) and cohesion (water molecules being attracted to each other). Therefore when water evaporates from the top of the leaves it changes the pressure in the vessel and pulls up the column of water to replace the water lost.

The best way to consider this is to imagine you have a thick shake – the straw can’t carry the shake up it, but if you suck from the top, you change the pressure and force the shake up the straw. It moves in a column because the molecules are attracted to each other.

What food colouring should I use?

We have found that natural food colours don’t work. These Wilton Gel Colours work for us every time.

Colour Changing Flower Experiment


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There are 46 comments

    1. ScienceSparks

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

    1. ScienceSparks

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

    1. ScienceSparks

      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! 🙂

  1. mummiafelice

    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

  2. Christy

    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?

  3. Why do plants need water? | Science Sparks

    […] Transpiration is the process by which water moves up the stem of a plant from root to leaf when water is lost from the plant due to evaporation occurring at the leaves. This continual flow of water and nutrients  keeps the plant’s cells firm, if the cells become short of water they lose firmness and the plant starts to wilt. […]


    […] of this process is where water travels from the roots of a plant to the leaves, we call this transpiration, which is driven by capillary action. This experiment is a simple, effective, and exciting way to […]

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