Everyone has seen those bright blue hydrangea flowers and probably fallen head over heels in love with them. All the greater is the disappointment for the amateur gardener when he discovers that the purchased plant suddenly changes color or does not produce blue at all. Or the reverse case: blue hydrangeas emerge, although the inflorescences were originally pink. But do not despair, because with the next bloom you can influence yourself which of the two colors you will see. Seems really handy to add some variety now and then, without having to replant the whole garden. What you need if you want to change the color of your hydrangeas, and how exactly to do it, we explain today!
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How do hydrangeas turn blue or pink?
So, if you have bought a shrub with blue flowers and the hydrangea loses color, you can either accept it that way, or color it again. As mentioned earlier, the original color of the blue hydrangea is actually a pink. So these are not white varieties that have been recolored by dyes, as is the case with many cut flowers. But how does it work then? How to change the color of hydrangeas?
Change the color of hydrangeas by changing the soil properties.
If you change the properties of the soil, it will cause hydrangeas to change color. So “coloring” is actually not the right word, because no new colorant is added to it. The pink base is affected by several things:
- how strong the original pink shade of the flowers is
- how high the aluminum content is
- the pH of the soil
- the hardness of the water when watering
For this reason, the hydrangea’s flowers may change color even though you didn’t want them to. Something may have simply changed naturally in the soil. By counteracting this, you can also change the color again from your hydrangeas.
Evoke blue hydrangeas
If you want to turn your hydrangea blue, you should change the properties of the soil (or keep it the same if the flowers have always been blue before). Usually, the garden soil is neutral. But what does the plant need to turn blue?
- the pH of the soil must be acidic
- the plant needs aluminum
How do you achieve this?
You have several means at your disposal to create an acidic soil and thus influence hydrangea colors. Firstly, it is recommended to use special rhododendron soil. This type of plant likes it acidic, so the soil is exactly adapted to these needs (hydrangea soil is also suitable). Organic fertilizers such as compost, peat or mature livestock manure also create an acidic environment, which they can support with fertilizers containing sulfur. If you also care about coloring hydrangeas with home remedies, you can water hydrangeas with vinegar diluted with irrigation water. The goal is a pH between 4 and 5, which you should measure regularly.
Once you have reached the right pH, you should take care of giving the plants the necessary aluminum so that the hydrangeas can change color. For this you can buy either so-called hydrangea blue or aluminum sulfate. Fertilizer that contains a lot of potassium but less phosphorus is also suitable. Aluminum sulfate you administer in the form of a solution of one liter of water and two tablespoons of the aluminum powder. How to properly apply hydrangea blue, it is noted on the package. You can also buy alum powder. But here make sure that it is potassium aluminum alum (from the pharmacy), because now the name “alum” is also used for other means.
How to make the flowers pink?
What conditions must be present if you want to turn hydrangeas pink? In principle, here the plant needs the exact opposite of what it needs for the blue flowers, namely:
- the pH of the soil must be alkaline
- the plant must absorb less aluminum (which is achieved by the alkaline soil).
How do you achieve this?
So, the soil must have a higher pH to avoid blue coloration. It becomes alkaline by giving it, for example, lime . Repeat this process several times a year and check the pH regularly. Once this is “6”, the soil is sufficiently alkaline to promote pink flowering.
Note: Be careful, however, that the plant does not suffer a nutrient deficiency. Especially iron deficiency is not uncommon and leads to yellow leaves. Prevent this with the help of fertilizer specially designed for hydrangeas and containing additional iron. Twice a year it is enough to fertilize the bush with it.
Is it possible to change the color of hydrangeas from white to another?
Would you like to change the color of white hydrangeas? For the coloring of pink/blue flowers is responsible a substance called delphinidin, which is naturally contained in the plant. This very substance can be influenced by the acidity of the soil. White hydrangeas, however, do not possess this basic substance, which is why color change, as described above, is not possible here.
Causing red flowers
Was your plant red when you bought it, and now you would like to have that shade back, or rather, would like to try to maintain it? If you would like to color the hydrangeas red, proceed in exactly the same way as if you would like to evoke a pink color. The shade of red is basically a precursor to pink and requires a more alkaline to neutral soil. However, keep in mind that you can never create a strong red, but the hue will always tend to pink.