When flowers absorb water from a vase or container, they also absorb any nutrients and additives in the water. Florists often use dying techniques to heighten or change a flower's colour before offering the flower for purchase. During holidays and special events, many types of flowers can be dyed colours that are not available naturally such as green carnations for St. Patrick's Day. Hydrangeas grow in shades of pink, blue and white. Dye a cut hydrangea to heighten its natural colour, or create one-of-a kind blooms for special occasions.
Add a pint of lemon-lime soda to the flower vase and then fill the remainder of the vase with lukewarm water.
Drop 1 tsp of bleach into the vase and then add a few drops of food colouring to the water. More food colouring will result in a deeper colour on the dyed hydrangea, while less food colouring will create a more subtle dye.
Cut the stem of a white hydrangea at a 45-degree angle while submerged in lukewarm water.
Place the hydrangea into the vase before the stems dries. As the flower draws in the water from the vase, the food colouring seeps into the flower's petals and changes the colour of the petals. Add additional food colouring as desired to deepen the colour of the petals.