How do I get Hydrangea bushes to produce purple flowers like on cape cod?

I live just north of cape cod. My hydrangeas already produce blue flowers.

How do I get Hydrangea bushes to produce purple flowers like on cape cod?
My parents (on Cape Cod) stick long nails in the ground near the roots to turn them purple. Cheaper than acid fertilizer!
Reply:acid soil, this is advice from my gardening guru mother
Reply:Hydrangea are fun plants..you can make them go pink by fertilizing with Acid Fertilizer, or make them go Blue by adding Lime around their roots (ground under bush). Have at it.
Reply:there are many different varieties and colors of hydrangea. most fall into pinkish, blueish, or white. soil PH greatly affects them. among other things, lime to raise PH, sulfur to lower it. you can even put one on one side and one on the other and have more than one color on the same plant. experiment, have fun with it.
Reply:I think it needs an acid soil. I'd try Mir-Acid (its an acid form of the fertilizer Miricle Grow.)

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