On the heels of my last post on hydrangea care,I thought an honest dialog about hydrangeas and their color changes would be a logical follow up dialog. First and foremost….white hydrangeas can NOT be changed to blue or pink by the grower. This would include PeeGee, Oakleaf, Annabelle and Limelight varieties. The white or light green colored blooms can change to various shades of pink and red as they age. But the initial bloom color remains white or the light green. The mop head and lace cap hydrangea that come in a blue or pink color are the only ones your can alter color to some degree.
It is however important to note that one can rarely change the intensity of the color. The intensity develops as a result of the particular variety of the hydrangea, weather conditions (heat, cold, humidity or dryness) health of the plant, and other natural factors. By fertilizing the plant 2x annually this could result in more saturation of color simply due to improved plant health. Some varieties tend more toward a pink or blue color they may not retain their colors if soil condition does not support.
So how does one attempt to change your hydrangea color? Lets start with the pink variety. Essentially for this color to remain, the plant must not uptake aluminum from the soil. By adding dolomitic lime several times a year, this will help raise the ph level. You want to achieve 6.0 to 6.2. Hydrangeas tend to uptake aluminum from the soil with a lower ph…so raising ph will reduce aluminum uptake and that bluing effect. You will also want to use a fertilizer that has has a high level of phosphorus. (that’s the middle number of the 3) Hydrangea gurus suggest a fertilizer close to 25/10/10.
To achieve a blue hydrangea color, aluminum must be present in the soil. So to assure it is available in your soil, you can add aluminum sulphate around the base of the hydrangea. Hydrangea growers and specialists recommend solution of 1 tbsp. of aluminum sulfate/gallon of water applied throughout the growing season. they do stress that the plant must be 2-3 years old. But use caution. General watering of plant should occur before applying the aluminum sulphate solutions, as you can burn the roots. So be careful! To assure the aluminum is available to the plant,(this is general chemistry folks) the soil ph should be low….5.2-5.5. Adding grass clippings or other organic matter to the soil is a functional, organic way to lower soil ph.
It is important to understand, that ground conditions change and so can the colors on one hydrangea plant. The best way to get the total color of course is having the plant in a container, as hydrangea growers do. This assures the proper conditions. So use these tips merely as a guide and enjoy the variety that nature provides us throughout the growing season
