Hydrangea -- Color

By The Old House Web
The color of some hydrangea can be changed by modifying the soil pH.

Hortensia hydrangea (Hydrangea macrophylla) will turn blue if the soil is on the acid side. Fertilize yearly with an acid fertilizer according to direction; modify the soil when planting with two (2) pounds of sulfur and peat moss. A pH between 4.5 and 5.5 is desirable.

To turn flower pink to light red, the soil should be neutral to alkaline. Use ground limestone ONLY around the plant if the color isn't pink. Pink colors occur between 6.5 and 7.5.

At pH levels higher than 7.5, chlorotic leaves and poor growth results.

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