Key Takeaways

Bloom color is generally controlled by soil pH and aluminum availability.

Only certain hydrangeas can change color, and some cultivars will stay white no matter what you do to the soil.

Color shifts happen slowly, often taking a full season or more.

Hydrangeas are one of those hardy perennials that can feel almost magical: One year, your neighbor has a surge of sky-blue blossoms, the next they’re a blushing pink. But hydrangeas changing colors isn’t random—it’s some basic chemistry at work in the soil (think back to that pH experiment in science class).

By making a few easy soil adjustments, you may be able to influence whether your hydrangeas lean blue, pink, or somewhere in between. To explain the method behind it, we turned to horticulture experts who specialize in

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