Naturally pink hydrangeas will turn blue under certain soil conditions. Responsible for this is the pH value of the soil, which must be in the acidic range. Only then can the hydrangea absorb enough aluminum sulphate from the subsoil. In the following article we explain how you can influence the soil conditions so that the hydrangea blooms permanently blue.

Hydrangeas need very acidic soil to turn blue

Acidic soil as a basic requirement

So that the hydrangea can absorb the trace elements responsible for the blue color from the soil, the soil must have a pH value of less than 4.5. However, only a few garden soils are so acidic.

remedy

  • Replace the topsoil with special hydrangea or rhododendron soil when you plant the hydrangea.
  • Analyze the pH value regularly with test strips from garden retailers.
  • If this value is too high, it can be lowered by sub-amounts of composted leaves or mature compost.
  • Watering with vinegar water also lowers the pH value.

irrigation water

Liming causes the pH value of the soil to shift towards alkaline and the hydrangea loses its beautiful blue colour. Therefore, in regions with calcareous water, only water the plant with soft rainwater.

Dyeing a hydrangea blue

For a pink hydrangea to turn blue, acidification of the soil is usually not enough. In addition, you must supply the earth with the aluminum responsible for the blue color.

You can either add commercially available hydrangea blue or alternatively potassium alum to the irrigation water. Out of respect for the environment, please follow the instructions on the packaging.

Discoloration occurs slowly

It can take up to two years for the hydrangea to turn fully blue. At first, attractive intermediate tones such as violet or a bluish pink appear. Usually even the flowers of an umbel are shaded differently, which gives the plant a special charm.

tips and tricks

The rumor keeps circulating that coffee grounds and ground egg shells as fertilizer turn the hydrangea blue. In fact, eggshells add calcium to the soil. Coffee pomace improves the soil structure and shifts the pH value into the acidic range. On their own, however, these measures are only sufficient if the garden soil is relatively acidic anyway.

Category:

Vegetable garden