Hydrangea & Calcium Deposits

About Soil pH

• Experienced gardeners know that soil pH has a significant effect on garden plants. Many plants require a particular pH range in order to uptake soil nutrients effectively. When soil becomes too acid or too alkaline for a particular kind of plant, it can suffer from nutrient deficiencies that affect appearance, growth rate and blooming ability. The pH scale ranges from zero to 14, with 7 being the neutral value. Soil that tests below 7.0 is said to be acidic. Soil that tests above 7.0 is considered alkaline.

Lime & Garden Soil

• Some areas of the United States have alkaline soil that contains large amounts of calcium deposits. Other areas may have more acidic soils without much calcium available for plants. Garden lime, calcium carbonate is a soil component often added to increase the alkalinity of soil. Calcium carbonate is worked into the top 6 or 8 inches of soil to raise the pH and allow greater nutrient availability for alkaline-loving plants.

Changing Hydrangea Color

• Hydrangea macrophyllla have the special ability to change color when certain materials are added to the soil. Highly acidic conditions cause the blooms to turn blue. Alkaline conditions turn the flowers a pink color. This allows gardeners to manipulate the color of the blooms whenever they want to add a different color note to their garden areas. Sprinkle 3 to 4 cups of lime around the base of the shrub and water into the soil. Repeat this three months later to keep the pink color.

Hydrangea Color Problems

• Not all hydrangeas change color, so ensure that you have a cultivar that is capable of color change before you attempt to add calcium carbonate to the soil. If adding calcium deposits to the soil does not produce the pink color you desire, it may be because of excessive amounts of aluminum in the soil, which works to keep the color of the blossoms blue. Adding additional amounts of calcium carbonate to the soil helps to counteract this blue tendency.