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 color before offering the flower for purchase. During holidays and special events, many types of flowers can be dyed colors 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 color, 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 coloring to the water. More food coloring will result in a deeper color on the dyed hydrangea, while less food coloring 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 coloring seeps into the flower's petals and changes the color of the petals. Add additional food coloring as desired to deepen the color of the petals.