Garden hydrangea

How to keep your blue Magical Hydrangea blue

It can happen: you buy a blue Magical garden hydrangea, and see the flowers’ initial colour become permanently pink in the following year (so we're not talking about the promised Magical colour change). Why is that? Well it’s a natural process that is caused by a pigment reaction. The good news is: you can do something about it.

To keep your blue Magical blue, do the following:

• In the first half of September, sprinkle the earth with aluminium sulphate or potassium alum. Do this carefully so that the sulphate does not land on the flowers or the leaves.
• If the flowers still change colour a bit, place the plant in lightly acidic peaty soil with a pH value of 4 to 4.5. You can measure the acidity with pH strips.
• And finally: the blue Magical prefers rainwater to tap water. The latter contains calcium, which causes the flowers to turn pink.