You and your friend live in different states and plant identical hydrangea bulbs in your garden. When they bloom, you send each other pictures. You notice that even though you bought the exact same kind of plant, your hydrangea flowers are blue and your friend’s are pink! On a hunch, you each measure the pH of your soil and find that your soil is a little acidic and your friend’s is a little basic. Why do you think the flowers have different colors?

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