Features

• The ideal soil for hydrangeas has lots of moisture and good drainage. For optimal plant health, use soil in a pH range between 5 and 7.
  
  

Preparation

• To increase a soil's acidity in preparation for hydrangeas, add a mixture of two parts sphagnum peat moss and one part potting soil into the planting area. Gardeners with a soil pH of 7 or higher should use the recipe to keep their plants healthy. A layer of mulch over the soil's surface holds in moisture; an acidic mulch helps maintain the soil's pH balance.
  
  

Bloom Color

• More acidic soil makes hydrangea blooms more blueish, while less acidic soil makes hydrangea blooms become more pink. Blue flowers occur in soils with a pH lower than 5.5, purple flowers in soils with a pH between 5.5 and 6.5, and pink flowers in soils with a pH above 6.5. The National Gardening Association suggests adding 1/2 cup of sulfur per 10 square feet of soil to make blooms more blueish or adding 1 cup of lime per 10 square feet to make the blooms more pink.