How to Change A Hydrangea Plant Color To Blue
Certain hydrangea plants can produce pink or blue blooms. The color of Hydrangea macrophyllia depends on the specific cultivar and aluminum availability, according to the U.S. National Arboretum. Only H. macrophylla and Hydrangea serrata bloom in colors other than white and can change color based on soil acidity, according to the University of Maryland Extension. Florist hydrangeas are hybrid plants and won't change color. Does this Spark an idea?
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Instructions
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Water the hydrangea daily for a week so that the plant is well-hydrated.
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Mix 1 tbsp. of aluminum sulphate per gallon of water. Use up to 2 gallons per plant. Drench the soil in a 2-foot radius at the base of the hydrangea with the mixture beginning in February. Keep the aluminum sulphate mixture off the leaves to avoid damage to the hydrangea's foliage, Professor of Environmental Horticulture Gary W. Knox at the University of Florida website advises.
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Repeat the process of drenching the soil under the hydrangea with the aluminum sulphate mixture in March and April.
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Reapply the aluminum sulphate treatment every year to maintain your blue hydrangeas.
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Tips & Warnings
Hydrangea macrophylla is also known as a French hydrangea, bigleaf hydrangea or big leaf hydrangea.
Hydrangea serrata comes from Japan and Korea. H. serrata is a version of Bigleaf Hydrangea with a finer texture, according to the Norfolk Botanical Gardens. The blooms are the flat, lacecap shape.
Garden centers carry aluminum sulphate. Aluminum sulphate is also known as alum.
Avoid increasing the amount of aluminum sulphate you use; too much aluminum can be toxic to other plants.
Don't use lime near your hydrangeas -- lime encourages hydrangeas to turn pink.
Keep fertilizers out of reach of children.
References
- United States National Arboretum; Hydrangea Questions and Answers: How Do I Change the Color of My Hydrangeas?
- University of Maryland Extension; Why Won't My Hydrangeas Bloom?; Phyllis Heuermann
- University of Florida IFAS Extension; French Hydrangea...; Gary W. Knox; April 1007
- Norfolk Botanical Gardens; Hydrangea; 2009
- Photo Credit Jupiterimages/Photos.com/Getty Images
