The hydrangeaswith their large flowers, fill gardens and terraces with color during the summer months.
Its most common tones are blue, pink and white.and whether they have one tone or another depends largely on the characteristics of the land that feeds them. The most curious thing is that the color of some varieties may change if the conditions and components of your soil change.
What does the color of hydrangeas depend on?
Originating from areas of Southeast Asia such as Japan, China or Korea, as well as South America, hydrangeas They are plants of the genus Hydrangea deciduous that can measure between 1 and 3 meters in height (depending on the species).
Its large flower heads, which They bloom between spring and early fallthey are usually colored in the ranges of blue and pink (purple, reddish, lavender…), or white. And one of its most surprising features is its ability to change color depending on the pH of the soil and the amount of aluminum it has (and the variety).
The presence of aluminum on earth It is the main factor that determines flower color: hydrangeas can absorb and metabolize aluminum and in doing so produce blue flowers.
Soil pH also influences
However, it must be taken into account that Soil pH affects aluminum availability so that the hydrangea absorbs it. Acidic soils (with a pH less than 5.5) allow aluminum to be soluble and the plant can absorb it. On the other hand, alkaline soils (with a pH greater than 7) retain aluminum.
So, acidic soils will produce blue flowerswhile alkaline soils will produce pink flowers.
A land with a neutral pH (between 5.5 and 6.0) is more likely to produce purple or lavender flowersthe result of mixing blue and pink.
On the other hand, The specific variety of hydrangea also influences the color of the flowers. Some cultivars are genetically predisposed to produce blue or pink flowers regardless of soil conditions and will not be able to change color even if soil conditions are changed (or will change very little). Additionally, you should know that when mature hydrangeas are white, they will not change color because this is determined by their variety.
How can you change the color of hydrangeas
Since the color of hydrangea flowers depends, to a large extent, on the characteristics of the soil, if we modify them we can change it. However, in those varieties in which the color is genetically determined this will not be possible.
Changing the pH of the soil will obviously be much easier in the pot-grown hydrangeas and it is advisable to do it a couple of months before flowering begins.
How to acidify the soil to have blue flowers
If you have pink flowers and you want them blue (or if you simply want to intensify their blue tone), you should make the soil more acidic (so they can absorb the aluminum). To do this, you can add organic matter such as coffee grounds, fruit or vegetable peelings, grass clippings, vinegar or citric acid to reduce the pH of the soil to between 5.2 and 5.5. Vinegar is a common fertilizer for acidophilic plants such as hydrangeas.
To better control the pH, another option is repot the hydrangea and use an acidic potting mix.
You can then add to the ground aluminum sulfate (you can get it at florists) to help the flowers acquire a bluish tone.
How to alkalize the soil to have pink flowers
On the other hand, if you want pink flowers, the soil must be alkaline so that it retains the aluminum and the plants cannot absorb it. In this sense, add dolomite lime to the soil It will help you increase the pH.
If what you want is lighten your pink or blue flowers until they have an almost white tone, you should get a very alkaline soil, with a pH of 8something that can cause health problems for the plant and is not advisable. The best to have white flowersis to buy specific varieties with that color.
You must keep in mind that modifying soil pH is a slow process that you must constantly monitor throughout the flowering season. The color change of flowers does not happen overnight and, to maintain it, you must constantly monitor the pH of the soil. To control it, there is devices that measure the degree of acidity or alkalinity of the soil and they can be very useful to you.