Colouring blue

The colour of the flowers of hydrangea is in general red, pink and white. Of most pink varieties the colour of the flowers can change into blue under influence of several circumstances. The possibility of a good blue colour depends on:

The variety: For instance: the soft pink coloured Hovaria® ’Hobella’ will –in phase one- stay pink, whatever we may try. The Hovaria® ’Homigo’ on the contrary can colour splendid sky-blue.
Acid soil (no lime or just a little) that also contains iron but especially aluminum.
Quality of water: Do not water with calcium water but with rainwater.
Fertilizing: Do not fertilize from August up to and including March and the rest of the year very sparingly. The leaves and the flowers will be a little smaller but also stronger.

Shortly after the winter-season some peat with a little of dried cow-manure can be mixed in the upper part of the soil.

If the hydrangeas grow blue spontaneously you can be sure they grow in acid soil.

The blue colour can also be stimulated by using aluminum-potash or aluminum-sulphate. Every year, in the first part of September, you have to spread this –only once about 15-50 gram (½ - 2 oz.) per plant dependent on the size of the plant- around the plant and rake this into the upper part of the soil.

If next year you think the flowers blue enough, do not give anymore or give a lower dose.

A plant in acid soil needs not as much aluminum as a plant in calciferous soil.

Need alum / aluminum-sulphate for your blue Hydrangeas? Order here!

If pink hydrangeas in your garden are growing blue and you want them to be pink, just click here.

If the hydrangeas in your garden do not keep their blue colour even after aluminum-potash and/or aluminum-sulphate has been given, you can dig a hole of at least 50x50x50 cm (20x20x20") or bigger, put plastic in it, make a drain in the bottom so the soil in the hole will not be too soggy and take care that the roots in no way can grow in the surrounding soil. Put acid soil (for instance sandy peat or Rhododendron soil) into it. Plant in this a new hydrangea to be quite on the safe side. Hovaria® ’Homigo’ for instance is very suitable because with this variety you start with a good blue plant that already is in proper soil.

You also can take a big pot or tub in which you put the proper soil and after that you plant a nice blue Hovaria^® ’Homigo’ into it.

Click for tips about hydrangea as a containerplant.

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