Hydrangeas are beautiful plants that bloom in pretty shades of blue, pink, and purple. But is it possible for hydrangea flowers to change colors?
Some bigleaf, Lacecap or mophead hydrangeas (Hydrangea Macrophylla) have the ability to change the color of their blooms from pink to blue to purple based on the pH of the soil.
Not all varieties of hydrangea change color. Some hydrangeas, like the Oakleaf, PeeGee, or Annabelle types that are white or ivory in color, will not be affected by the pH of the soil.
Lacecaps are flat flowers with frilly edges, while mopheads have large, globe-shaped flowers. This includes varieties like Endless Summer, Nikko Blue, Summer Crush, and L.A. Dreamin. Although these varieties have blue or pink in their names, they can still change colors.
Why do hydrangeas change colors?
Hydrangea plants change colors based on the pH of the soil. The chemical makeup of the soil decides the color of your hydrangea blooms.
If the soil is high in aluminum and has a low pH, the soil is acidic and this will result in blue hydrangeas. And if the soil is low on aluminum or has a high pH, it is alkaline and the color of the hydrangeas will be pink.
A neutral pH between acidic and alkaline will result in hydrangeas that bloom in shades of purple.
How long does it take for the hydrangeas to change colors?
You can change the colors of your hydrangea blooms, but it is not an instant process.
The change of color can take weeks or even months. It also depends on the type of hydrangea and the color you want to change it to. Some cultivars are more prone to changes in colors than others.
Also, it is easier to change blue hydrangeas to pink than to change pink hydrangeas to blue.
After you plant the hydrangea, you need to wait for at least two years to try and change the color, so that the plant has enough time to recover from transplant shock.
How to change the color of your hydrangea?
Here are the steps that you can follow if you want to change the color of your Hydrangea.
Soil test is the First Step
The first step in changing the color of your hydrangeas is to get a soil test done.
Whether you grow your plants in a container or in the ground, you need to do a soil test to get accurate information on the pH of the soil. As you need to find out if your soil is acidic or alkaline in order to proceed further.
There are two types of soil tests. Either, you can get a home soil testing kit that you can use yourself, or you can get a professional soil test.
You can get a home test kit or a pH meter at any garden center or nursery. It won’t be as specific as a professional test, and you may not get N-P-K levels.
However, you can still get an accurate pH reading that you can use to amend your soil in order to change the color of the hydrangeas as you desire.
A professional soil test will be done in a lab. You can check in with the local county extension office or area universities who might know of labs that can do this procedure for you.
You can send in the soil samples there to get a very accurate and detailed reading of your soil.
Change the color of hydrangeas to blue
To change the color of hydrangeas to blue, the soil needs to be acidic.
For that, aluminum needs to be present in the soil. You can add aluminum sulfate to the soil around your hydrangeas in order to ensure a supply of aluminum.
Here are the steps.
- 1 tablespoon of aluminum sulfate for 1 gallon of water can be applied to the plants throughout the season.
- The plants must be at least 2 to 3 years old.
- Water the plants in advance before applying the solution.
- Make sure you apply it carefully, as an excess of it can burn the roots of the plant.
- Adding aluminum sulfate will lower the pH of the soil.
You can also add organic matter like compost, coffee grounds, fruit and vegetable peels, etc. to keep the pH low.
Crushed eggshells, as well as ground-up citrus peels, can also help increase the acidity of the soil.
Many gardeners use vinegar in the water while watering hydrangeas in order to increase the acidity of the soil and turn the flowers blue.
Fertilizing with high potassium and low phosphate fertilizer will also help increase the uptake of aluminum. You can use ammonium sulfate as a source of nitrogen to keep the pH low.
You should avoid using superphosphates and bonemeal if you want blue flowers. Hydrangea Blue, a liquid fertilizer, also helps in producing blue flowers.
If the soil is naturally acidic and contains aluminum already, the color of the blooms will automatically lean towards shades of blue or purple.
You might also want to get your water tested if you really want blue hydrangeas. The pH of the water should not be higher than 5.6, as it will disturb the balance you have created and make a difference in the pH of the soil.
Even after all this, if the soil is highly alkaline and contains no aluminum, it might not be possible to grow blue flowers at all.
The only thing you can try if you wish to grow blue hydrangeas even in alkaline soil is to grow them in containers.
That way, you can use a lot of compost to keep the pH level down. And it will be much easier to control the conditions required for growing blue hydrangeas.
If you have planted your hydrangeas near a concrete structure or the sidewalk, it will affect the color of the flowers.
The limestone in the concrete will leach into the soil, making it difficult for the plant to get blue-colored blooms.
Change the color of hydrangeas to pink
If you want to change the color of your hydrangeas to pink, you will need alkaline soil.
For this, the plant needs to avoid taking up any aluminum from the soil. If the soil already contains aluminum, you need to make sure it does not enter the hydrangea’s system.
It is harder to change the color of blue hydrangeas to pink, as there is no way to remove the aluminum from the soil.
Here are the steps that you can follow to change the color of your hydrangeas to pink.
- Adding dolomitic lime to the soil several times a year will help raise the pH of the soil.
- You need a pH of about 6.0 to 6.2.
- If the pH is more than 6.4, the plant may suffer from an iron deficiency.
- Hydrangeas take up aluminum better when the soil is acidic, so raising the pH of the soil will ensure that the process of the flowers turning blue because of the uptake of aluminum does not take place.
- You will need to use fertilizers that have higher levels of phosphorous. Phosphorous helps prevent aluminum from seeping into the hydrangea plant.
- You can also add lime to the soil over the area of the roots of the plant. It will be at least 1 to 2 inches outside the edges of the plant.
- You might need to repeat the treatment to get pink hydrangeas, and even after that, you will need to keep up the treatment.
If you live in a region where the soil is acidic and grows blue hydrangeas, you might want to consider growing your hydrangeas in containers.
This way, you can control the requirements necessary for growing pink hydrangeas. Using a soil-less mixture for your potting mix will ensure that there is no aluminum in there.
Change the color of hydrangeas to purple
Hydrangea flowers can turn shades of reddish-purple to pale-purple or lavender when the soil is around the neutral mark.
Often, you might get purple flowers while you are in the process of raising or lowering the pH to get pink or blue colors.
If you want to get purple blooms, you will need the pH of the soil to be somewhere between 6.0 to 6.9.
What to remember while trying to change the color of hydrangeas?
One application of soil acidifier will not be enough. You will need to apply it at least 2 to 3 times a year.
White hydrangeas cannot be changed to blue or pink. Some species, like The Almighty, can get hues of red or pink as they age, but the flowers will not completely change colors.
A true red hydrangea can rarely be obtained if you live in a hot climate. Even if you add a lot of lime, you will only get a very deep pink.
It is not easily possible to change the intensity of the color. You can change the colors from pink to blue to purple. But it will be difficult to change how strong or pale the color is.
This is because the intensity of the color depends on a lot of factors. They include the heredity of the variety of hydrangea, climate and temperature of the region, the health of the plant, etc.
Sometimes, just fertilizing a hydrangea once or twice a year can result in a more saturated color as the health of the plant improves.
There are a few varieties that lean towards either pink or blue colors. But if the soil conditions are not right, they will not be able to retain that color.
The L.A. Dreamin variety can feature all three colors – pink, blue, and purple at the same time.
Hydrangeas start fading naturally as fall season approaches and dry out.
A tip – Try to use rainwater instead of tap water wherever possible, as hard water can affect the color of the blooms.
Hydrangeas at a florist’s
You will notice that hydrangeas at a florist shop are always vibrant and saturated with color.
You never seem to get that intensity with the blooms in your garden. This is because the growers make a lot of alterations to the soil from the beginning and throughout the growing process.
The small brightly colored plants that you see are also bred to have bigger blooms.