HORTENSIAN COLOR CHANGE TIPS
Influencing the color of the hydrangea
The color of the hydrangea is influenced by the acidity of the soil. Under neutral conditions (pH value between 5.5 and 6.5) and without too much aluminum in the soil, the hydrangea takes on its normal color. With more lime in the soil, the color turns pink. Acidic soil with aluminum sulphate causes a discoloration to blue. But remember: a light pink hydrangea will never turn dark blue. It will always change color to light blue.
Each hydrangea has its own preferred color, but let’s say you have a pink hydrangea and you want it to fade to blue. Two factors are then important. Firstly, you need acidic soil, for example by adding garden peat, then you get a low pH value. Second, there must be metal ions in the soil. You do that by throwing in alum, aluminum sulfate or even your old nails. What happens then: the pink color slowly changes to blue.
If you want to have the blue hydrangea color back to pink, you should sprinkle lime on your hydrangea. Then the acidity of the soil decreases and you will see that that blue color slowly disappears again, sometimes through purple it turns pink again.