The hydrangea plant is the only known plant that can 'detect' the pH level in surrounding soil!
The more acidic the soil is, the more likely the sepals of the hydrangea bloom will be blue or purple; however, the more basic the soil is, the more likely the sepals of the hydrangea bloom will be pink or red.
There are more twists in this curious chemical process! To read more, visit this link: americanscientist.org/issues/feature/2014/6/curious-chemistry-guides-hydrangea-colors.
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