How to Change the Color of Hydrangeas
Process of changing colors is based on manipulating the light received by the plant and chemical composition of soil used. Change in soil pH brings about desirable changes in the color of hydrangeas. Checking or testing the pH of soil is the first step in the process of changing it and color of flowers.
Raising the soil pH any higher in order to make it alkaline, won't be of much help. Just maintaining the 6.0-6.5 range is recommended. Adding soil amendments like high phosphorus fertilizers to the soil also helps in reducing aluminum absorption by soil.
Aluminum is naturally present in almost all soils, and so, one can change the color to blue easily. Even if the soil is acidic and there is natural presence of aluminum, the addition of aluminum sulfate should prove to be useful. To maintain the blue color, one should add fertilizers that are low in phosphorus content and have higher percentage of potassium.
There are many factors which play a role in the alteration of shades of hydrangea flowers. Some of these factors include temperature, humidity, and heredity of hydrangea varieties. At the most, one can attain a saturated color by fertilizing it once/twice every year.