Keeping your hydrangeas blue
QI understand that blue hydrangeas need a certain type of soil to keep their colour. Is this correct? Mrs B Whittick, Morden, Surrey
AThe flower colour of types of hydrangea plants varies according to the pH (alkalinity/acidity) of the soil or compost in which they are growing.
They have pink or mauve flowers in neutral to limey/chalky soils, whereas in acid (ericaceous) soil/compost the flowers are lilac to deep blue.
You can buy hydrangea colourant (such as Glowing Success Hydrangea Colourant) that can be used to keep blue hydrangeas blue or turn pink ones blue.
Hydrangeas with white blooms are unaffected by soil pH, but will sometimes turn pink as they age.
Acid soils cause blue hydrangea blooms