Hydrangeas are popular because they have beautiful blooms. They can be white, pink, or blue, and they can actually change colors.
Lacecap and mophead hydrangeas can change from pink to blue or blue to pink depending on the pH level in the soil. If you want to make your hydrangeas pink, you can modify your soil conditions.
Why Do Hydrangeas Change Color?
Hydrangeas will change color based on the amount of aluminum and the pH level in the soil where they are planted. This doesn’t happen with white hydrangeas, but it happens with blue and pink varieties.
When the soil is more acidic, there is plenty of aluminum for the plant to use. The hydrangeas absorb it through their roots.
On the other hand, in alkaline soil, the plants don’t have access to the aluminum. You might plant a blue hydrangea one year, and it could bloom pink the following year because your soil is too alkaline.
If the soil is acidic, the plant will bloom blue. You can change the color of bigleaf hydrangeas that are pink or blue by changing the pH levels of your soil.
Start by Getting a Soil Test
The first step to understanding your hydrangeas is to get a soil test. It is best to opt for a professional test to get accurate readings of your pH levels.
You can also get a pH meter that will measure the pH in the soil. Once you know how alkaline or acidic your soil is, you can add to it to choose the color your hydrangeas will bloom.
If you want to get a professional test done, you can call your county extension office or universities in the area.
How to Test Your Soil at Home
Start by gathering a sample of your soil. You should dig a hole that is four to six inches deep, remove the soil from the bottom of the hole, and place it in a container made of glass or plastic.
You only need a teaspoon of soil, but you can take a little more and mix it up. If you want to test a few areas, you can mix them together.
Make sure that you use gardening tools, and break up any clumps with a trowel. You shouldn’t use your hands because you can actually affect the pH level of the soil.
Wait for your soil to dry, and then place a small amount into the vial that comes in the test kit. Try to make sure that it is only soil without rocks or other substances.
Use a small spoon to get the soil into the vial, and don’t touch it with your fingers. The vial will have a line that tells you how much soil to add.
Next, you can open one of the capsules that comes with your kit and pour it into the soil. Once it is in there, use the plastic eyedropper to fill the vial all the way to the top with distilled water.
Using distilled water is ideal because it is neutral, whereas your tap water may not be.
Now you can place the lid on your vial and shake it. Continue shaking it until you see the soil and the powder completely mixed with the water in the vial.
You should put the vial down and let the soil settle for 60 seconds before you check the color. Then, compare the color that you see with the chart that is on the vial.
You will find out the pH level of your soil, and then you can decide what you want to do to make it work for the color you want your hydrangeas to be.
How to Change Your Hydrangea to Pink
If you want your hydrangea to bloom pink, start by making sure that you have bigleaf hydrangea in the pink or blue variety. Then you have several options.
You should consider testing your soil so that you know the pH level. The basic rule of thumb is that when the pH of the soil is between 6.0 and 6.2, the blooms will be pink, when it is between 5.5 and 6.5, the blooms will be purple, and when it is 5.5 or lower, you will have blue blooms.
If you want to make your hydrangeas bloom pink, you can add lime to the soil; for blue blooms, add aluminum sulfate. The amount you need is based on your soil composition.
Of course, you can control the pH of the soil much more easily if you keep your hydrangeas in a container, so this is a consideration if you need the plant to bloom pink or blue.
Myths About Hydrangeas
Because hydrangeas can bloom different colors, there are many myths out there about these plants. You may have heard that they are difficult to grow, but the fact is that as long as you give them what they need, they aren’t hard at all.
Myth #1: The “Hydra” in Hydrangeas Means That They Need a Lot of Water
This is one of the most commonly spread myths about hydrangeas. When you break down the meaning of the name, it is easy to understand how someone started this rumor.
Hydra comes from the Greek word hudra, which means water. Angea comes from the Greek word angeion, which means pitcher or vessel. Some say that it is named this way because it looks like a water pitcher, while others say that the three red stems that hold the seeds look like a water vessel.
Either way, it was named for its appearance, not due to any excessive need for water. Hydrangeas need approximately one inch of water (including rainfall) each week through the growing season.
If you hear this myth and overwater your hydrangeas, you can kill them quickly.
Myth #2: Use Fertilizer to Make Hydrangeas Bloom
You may hear people say that hydrangeas will bloom if you add fertilizer. Fertilizer adds nutrients that are lacking in the soil, and if nothing is lacking, the fertilizer won’t help your hydrangeas bloom.
The biggest problem with this myth is that sometimes people over-fertilize, which can have the opposite effect. You may end up with beautiful deep green leaves, but you won’t have any flowers.
If your hydrangeas are not blooming as expected, there are a number of possible reasons, but adding fertilizer when the soil doesn’t need it isn’t the solution.
When you prune hydrangeas, it is easy to cut off the wood that is prepared to bloom in the spring. If you cut them back, you will actually cut away the blooms, and it won’t flower.
Hydrangeas can be sensitive to cold, and if your plant freezes over the winter, it may not bloom in the spring. A late spring frost can also prevent a bloom.
Your hydrangeas need at least three or four hours of light to bloom, so make sure that you have it in the right location. You should avoid feeding fertilizer that is high in nitrogen because it promotes leaf growth, but not blooms.
Myth #3: You Can Change the Color of Hydrangeas with Fertilizer
This is not true. The pH level of the soil influences the color of the bloom. It is based on whether the hydrangeas’ roots absorb aluminum.
Myth #4: The pH Changes the Color of the Bloom for Hydrangeas
While there are some hydrangeas that can change the color of their bloom, most of them are white, and the bloom changes colors as it ages. If you have bigleaf hydrangeas in blue or pink, they can change colors depending on the condition of your soil.
It is only these hydrangeas that bloom based on the pH level and the availability of aluminum. No matter what the pH level is of your soil, if you have no aluminum, the hydrangeas will not bloom blue flowers.
To understand the way that the pH level changes the soil, you need to know what happens. When you have soil with alkaline conditions, the soil holds the aluminum molecules inside it very tightly together, so the roots of the plant aren’t able to absorb them.
The bloom is pink when the roots can’t absorb aluminum. However, when the soil becomes more acidic, it releases the aluminum, and the roots can absorb them.
The availability of aluminum helps the hydrangeas turn blue, but if they only have some aluminum available, the blooms might be purple.
Myth #5: Add Aluminum to the Soil to Make Blooms Blue
While this could be true, it isn’t necessarily the case. If you have alkaline soil and add aluminum to it, the soil will pack it tightly so that it isn’t available to the roots of your hydrangeas.
The time to add aluminum is when your soil has the right pH level (is acidic) and simply lacks the aluminum you need. This works best when you have your hydrangeas in containers and can control the soil environment.
Myth #6: You Can Turn Hydrangeas Blue If You Bury a Nail Under the Roots
Some people say that you can bury various objects under hydrangeas, ranging from nails to razor blades, hairpins, and pennies. The problem is that there is no chance of this working unless a couple of things happen.
First, the object would need to be made of aluminum or mostly aluminum. Second, it would have to corrode right away to release the aluminum into the soil.
In addition, the pH of the soil would need to be conducive to releasing aluminum. The bottom line is that this trick doesn’t actually work.
If you want to add aluminum to the soil, you should make sure that the pH is in the right range and then add aluminum.
What Kind of Hydrangeas Can Bloom Pink?
When you are looking for pink-blooming hydrangeas, you have a few options. Although many hydrangeas bloom in white, there are a few that bloom in pink.
Among these, some bloom pink when the soil is alkaline with a pH above 7.1, and there are others that always bloom pink no matter what the soil pH is.
Hydrangeas that are considered mophead hydrangeas produce flowers that look like a mophead, and they will bloom pink when you grow them in alkaline soil. They can grow up to six feet tall, and there are a few smaller versions that grow to three or four feet.
Another type of hydrangeas is the lacecap variety, which is another version of the bigleaf hydrangea. These plants also grow pink blooms when they are in alkaline soil.
The panicle hydrangeas and oakleaf hydrangeas both produce white flowers that are shaped like a cone, but they do change to pink over time. This type of hydrangeas is not affected by the pH level of the soil.
Finally, there is a hybrid vine called the Roseum, and it does give out pink lacecap flowers at the end of the summer. This type is not affected by the soil either.
When to Treat the Soil to Change the Color of the Hydrangeas
The best time to treat your soil is in the spring or the fall. You want to make sure that your plant has enough time to absorb the aluminum that is released into the soil to change the colors.
Once you adjust the soil, it can take anywhere from a few weeks to a few months to actually change the hue of the bloom.
If you are looking to make a more significant change to the composition of your soil, you might want to treat your soil every two to four weeks. It is important to continue treating the soil because it will eventually return to its old pH.
Final Thoughts
Hydrangeas are a popular plant in many homes because they are beautiful when they bloom. One unique feature is that bigleaf hydrangeas can bloom in different colors depending on the availability of aluminum in the soil.
If you want your hydrangeas to change their bloom, have your soil tested and find out the pH as well as the aluminum content. Then, make the necessary adjustments to have them bloom in pink, blue, or purple.
Growing up with a mom who filled her home (inside and out) with all sorts of plants, Lisa got her start in gardening at a young age. Living now on her own with a home and yard full of plants (including an indoor greenhouse), she shares all the gardening tips she’s gained over the years.