Change the Color of Your Hydrangea
You can alter the color of your hydrangea flowers by increasing or decreasing the acidity of the soil. If you have blue or pink hydrangeas in your garden, you can change their color. However, acidity level in the soil has no effect on the color of white hydrangeas.
The main factor in the coloring of hydrangeas is aluminum absorption. If the pH of your soil is high, the hydrangea plant will not absorb aluminum from it. This will result in the production of pink flowers. Acidic soil encourages aluminum absorption, resulting in blue hydrangeas.
If you grow your hydrangeas in a pot or container, your task is simple, as you can easily manipulate the pH level and aluminum content.
Altering Soil pH
To change the color of blue hydrangeas to pink, increase the pH of the soil by adding agricultural lime. Do not increase the pH above 6.4, because the plant’s growth may be affected adversely. Provide high levels of phosphorus, which will aid in decreased aluminum absorption.
Increasing the aluminum content in the soil and lowering its pH will result in blue flowers. If your plant is well-established, add aluminum sulfate at the required rate, taking care not to overdose, which will result in burnt roots. You can also plant some aluminum nails or add compost in the surrounding soil. When fertilizing, make sure the phosphorus level is low. Water plants with distilled water so that the pH is not altered by watering.