Gardeners with serrated or bigleaf hydrangeas growing in a home landscape have the unusual ability of determining the color of their hydrangea blossoms. Whether the blooms become pink or blue and how intense the hues display depend upon the pH levels in the soil. Allow enough time to amend the soil and you should see the blossoms slowly change, depending upon whether the soil is acidic or alkaline. Turn hydrangeas pink by making the soil more alkaline (raising the pH level).
Measure 1 tbsp. of hydrated lime and pour it into your bucket or watering can. Add 1 gallon of water over the hydrated lime and stir to dissolve the lime.
Pour the hydrated lime over the soil around the hydrangeas, taking extreme care not to splash any liquid onto the plant foliage, because it will burn tender foliage. Pour the hydrated lime until you thoroughly saturate the soil.
Repeat the hydrated lime application two more times during the growing season throughout the spring months.
Apply the fertilizer to the soil during the spring and again in midsummer. Sprinkle ¼ cup of fertilizer around a small bush, 1 cup of fertilizer around a medium-size bush and 2 cups of fertilizer around a large bush. Scratch the fertilizer into the soil with the hand rake and water the soil generously.