Why are some hydrangeas dark blue but others are not?

Answer by  Marie (778)

Some hydrangeas are white, while others vary between blue and pink depending on the chemistry of the soil. For a hydrangea to bloom blue, it needs acidic soil.

Answer by  TejasWoman (300)

The deepness of the blue color in hydrangeas is due to the amount of iron in your soil. The more iron the deeper the blue. I remember my grandmother, many years ago, putting old rusty nails around the base of her hydrangea bushes because she wanted them to be a darker blue than the pale blue color they were.