This colour changing flowers experiment is a great way to see how water travels in plants and it’s really fun to see the flowers change colour! All you need is white flowers and food colouring (and a little bit of time!).

What you will need:

White flowers
Food colouring - A concentrated paste or liquid would work best as gel dye is usually not very pigmented.
Clear glasses/cups, bottles or jars - as many as you have food colours and flowers!
Water

First of all, you’ll need to gather some white flowers. Any type of flower will do and you can even use a mix of different ones and see which ones work best. If you’re picking your own flowers, then try to use them soon after picking. Bear in mind that more substantial flowers such as carnations, chrysanthemums and roses will last longer than delicate daisies like I used!

Prepare your dyes by half-filling your glasses/cups, bottles or jars with water and then mixing in a few drops of food colouring until your water is a nice deep shade of your colour. If you’re using narrow-necked or tiny bottles and thick paste food colouring like I did, you might want to mix the colour up in a separate container first. I really wanted to use the cute tiny little bottles from the May Mud & Bloom box so mixed the colours separately first!

You can also combine different colours of food colouring to make more dye colours. For example, blue and red food colouring to make a purple dye.

Trim down the stems of the flowers so they fit your cups or glasses, cutting the stems at a 45 degree angle. Cutting the stems at an angle will help to increase the absorption of water by providing a larger exposed area for the uptake of water. It also ensures that the base of the stem is not sitting flush with the bottom of the glass so that water is always in contact with the cut surface.

Place a flower in each of your glasses of coloured water.

Now wait for your flowers to change colour!

The flowers will start to change colour within an hour, with some colours appearing in the petals faster than others. The reason the flowers change colour has to do with how they soak up water. It is through capillary action that plants are able to defy gravity and pull the coloured water from the cup up into the stem, through the flower and into the petals. The longer the flower stem sits in the coloured water, the more of the dye the flower will absorb as it ‘drinks’ the water.

Interestingly, I found that the flower in the red water only changed colour very subtly and also that the flower in the purple water (at the back, on the right) went blue rather than purple - perhaps the red pigment particles were too large to be pulled up the tiny stem to the top of the flower?