There are many varieties of Hydrangea available. One of the most popular is the Endless Summer Hydrangea and depending on the pH of your soil the color of the flowers will change. By adding or subtracting aluminum you can control what color blooms your plant has. Colors range from pink to blue.
To get pink flowers the plant must not get aluminum. Here are a few tricks to keep the plant from taking up aluminum.
- Add lime to the soil a few times a year to raise the pH of the soil.
- Use a high phosphorus fertilizer.
- If all else fails try planting the hydrangea in a pot where it will be easier to control soil conditions.
To get blue flowers the plant needs to absorb aluminum. Here are some tips to get your Hydrangea to absorb aluminum.
- Add aluminum sulfate to the soil. Add 1 Tbsp per gallon of water to mature plants throughout the season. Apply cautiously, to prevent the solution from burning the roots.
- Lowering the pH of the soil will allow the Hydrangea to more easily absorb aluminum. This can be done by adding organic matter to the soil (compost, coffee grounds, grass clippings).
- Use a fertilizer low in phosphorous and high in potassium. Avoid bone meal as it is a superphospate.
- Avoid planting Hydrangea near concrete foundations or sidewalk as lime leaching from the concrete will raise the pH of the soil and make it difficult to keep flowers blue.
One last note...white Hydrangeas can not be changed to Pink or Blue. They may have a slight tint of pink to them, but will not change color.