Hydrangea is a flower that changes colour with the acid/alkaline content of the soil. It can be intense blue, not pictured here, to intense pink, indicating acid soil to alkaline soil, in that order, blue to pink.

On one side of our little stream the colour is blue-violet, indicating slightly acid to neutral soil and the right side is the pink bloom, indicating very alkaline soil.

Here in our garden there is a lot of old broken down shell in the soil (alkaline), hence we cannot grow big potatoes, but do well with beets. Zucchini never overwhelm us and in part of our garden winter squash blossom but do not fruit. We are good for beans, leeks and kale.