How to Get Hydrangeas Purple

Hydrangeas change color because of the chemical composition of the soil.

Hydrangeas have the ability to produce pink, purple or blue flowers. Their color depends on the pH and mineral content of the soil in which they are growing. Adding chemicals directly to the flowers will not change their color. Hydrangeas change color because of the chemical composition of the soil. You should let newly planted hydrangeas acclimate themselves for a full year before attempting to change their color by altering the soil composition. Chemical additives could be fatal to a young plant.

Things You'll Need

• Aluminum sulfate

Instructions

1. Water plants well with plain water and wait one day.

2. Mix 1 tbsp. aluminum sulfate into 1 gallon of water. Give each hydrangea bush about half a gallon of the solution once a week.

3. Add organic material to help lower the pH of the soil. Use organic material that is high in acid, such as coffee grounds, pine needles or peat moss.

4. Fertilize with a fertilizer low in phosphorus and high in potassium.

Tips & Warnings

• Aluminum sulfate is commonly used as a soil amendment and is available at garden centers and home improvement stores.

• White hydrangeas are white and cannot be changed to purple, blue or pink.

• If all else fails, bury a handful of iron nails in the soil beneath or right next to the plant.

• The pH of the water you water your hydrangeas with can undo all you have done to change them to purple -- it should be no higher than 5.6.

• If your hydrangeas are planted near a concrete foundation or sidewalk, it may be difficult to turn them purple. Lime that leaches out of the concrete may raise the pH of the soil enough to prevent the color change.

References

• All about changing the color of hydrangeas.