Answer: Hydrangea blooms color can be affected by soil pH. A somewhat acidic 5.5 should turn them blue, a more alkaline 6.0 should turn them pink with the effect being more intense the more extreme the pH. Pink and red hydrangeas often turn blue or purple in acid soils. Blue hydrangeas can turn pink in alkaline soils. Plants can be made (or kept) blue by applying aluminum sulfate to the soil; plants can be kept pink by liming the soil or applying superphosphate. Because you've added peat and pine needles to your soil, the pH will be on the acidic side. Do a soil test and add lime if necessary to sweeten the soil. It's best to apply amendments in February or March of each year so the blossoms will be the color you expect!
Your hydrangea will probably bloom this year (they don't take long to become established!) Enjoy!
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