If you have bought a red hydrangea, you would like to enjoy exactly this color of the romantic flower umbels. In this article you will find out why a red hydrangea suddenly has pink flowers and how you can turn the flowers of your hydrangea intensely red again.
How do you get a red hydrangea?
To obtain a red hydrangea, the pH of the soil should be in the alkaline range (about 6). Lime helps raise pH, while eliminating lime and adding compost or vinegar to irrigation water lowers pH and results in pink or blue flowers.
The color of the hydrangea depends on the substances in the soil
Hydrangeas need acidic soil to absorb the aluminum necessary for the intense color. If the soil is only slightly acidic or slightly alkaline, the flowers of the hydrangea always turn a delicate pink.
A dye from the anthocyanin group is responsible for the respective shade of the hydrangea flowers. The delphinidin forms a chemical bond with aluminum ions that the hydrangea absorbs from the soil. This is shown by the red or, in very acidic soils, purple or blue coloring of the hydrangea umbels.
Influence the pH value of the soil
For your hydrangea's flowers to turn red, you need to shift the pH of the substrate to the alkaline range. On average it should be 6 or even slightly above.
Deacidify the soil with lime, which you spread around the plant several times during the growing season. To avoid liming too much, it is recommended to measure the pH value before the first application of lime and to repeat this analysis at regular intervals.
Turning a red hydrangea pink
Perhaps you are re-planning the design of your garden and a red hydrangea no longer fits well into the overall picture. In this case, you can decolorize the hydrangea so that it bears delicate pink flowers in the future. You can do this like this:
- If you have shifted the pH value of the soil to the alkaline range, stop liming from now on.
- The substrate is acidified by adding mature compost and a mulch layer of leaves.
- Add a dash of vinegar to the water at regular intervals.
To ensure that the soil does not become too acidic, check the pH value of the vinegar water with test strips. We recommend that you also test the substrate regularly. If the soil becomes too acidic, the hydrangea will not turn pink as desired but, if the aluminum content is appropriate, it will turn blue.
Tips & Tricks
Even with optimal pH, a red hydrangea will never be as brightly red as a rose, for example. The color is always a bit pink.
