Why and How Hydrangeas Change Colors and What You Can Do To Influence It

Hydrangeas are indeed the showstoppers of a lawn or garden. Every spring and summer, you’ll find these lush green shrubs covered in large, colorful blooms ranging from soft white to dark crimson and every shade of pink, green, or purple in between. Unlike many cut flowers, Hydrangeas change color through natural means, like a litmus test for your garden.

Most Hydrangeas change color when the soil’s pH changes. Blue blooms are produced by more acidic soil, and pink flowers prefer alkaline soil. Some Hydrangeas, like those that bloom actual white flowers, do not change color. You can influence certain types of Hydrangea’s color by using soil additives to alter the pH.

In this article, I’ll explain in detail why and how some Hydrangeas change colors and discuss how you can change or improve your Hydrangea’s hue. I’ll also discuss which kinds of Hydrangeas won’t respond to soil changes by changing color.

Why Do Hydrangeas Change Color?

You may already know that Hydrangeas can switch between blue and pink, and you may even have an idea about why it happens. However, you probably don’t know about all of the science behind this color-shifting quality. Let’s take a closer look at this not-so-magical (but still very unique) process.

What is Soil Acidity? The pH level of soil refers to how acidic or basic it is. Understanding pH is a little tricky because the numbers may seem backward. pH is measured on a scale of 0-14, where 7 is neutral. Lower numbers indicate that the solution is more acidic, and higher numbers are more basic or alkaline. Since 7 is neutral, pH levels below 7 are acidic, and pH levels above 7 are basic.

Hydrangeas and Soil Acidity

Since you’re probably familiar with Hydrangea blooms, you know that they’re made up of many petals on a large, lush ball. Well, think again, because you don’t know Hydrangeas at all! (Neither did I, so don’t feel too bad). Hydrangea blooms are actually a cluster of many flowers, and those “petals” are called sepals.

The sepals on your Hydrangea act like tiny litmus papers, and their color reflects the pH of the soil, just like if you dipped a litmus paper into a solution in chemistry class. The colors follow the same pattern as the pH scale chart, which is actually pretty cool.

The pigments in Hydrangea blooms are called anthocyanins. These are water-soluble pigments that create the colors you see in fruits and veggies. These pigments are an essential part of why your Hydrangea changes color.

When these unique pigments are closer together and stacked on one another (we’re talking on a teeny, tiny, microscopic level), they appear blue to our eyes. When anthocyanins are farther apart, they look pink.

In acidic soil conditions, the pigment molecules can more easily move closer together, resulting in blue blooms. The opposite is true in less acidic conditions.

Hydrangeas and Aluminum Content in Soil

If you do a Google search for Hydrangeas, you’ll find information about soil acidity and color changes. However, many people don’t know that aluminum is an equally important factor in why these fantastic flowers can do their tricks.

The role of aluminum is a more recent discovery in the history of garden science. Aluminum ions interact with the pigment in Hydrangeas and impact the chemistry inside the plant. It’s a very complex and scientific process that you can check out this article in American Scientist if you’d like to learn more.

When the soil condition has a lower pH (or is more acidic), the aluminum ions can be absorbed more easily and move around inside the plant to interact with the pigments. Without aluminum, all Hydrangeas would likely just be red! Can you imagine?

Since aluminum is toxic to plants, Hydrangeas move the ions from the root systems and leaves into the blooms, turning the sepals blue!

Acidic soil → aluminum ions can move easier → increased aluminum uptake into the root system → blue Hydrangea bloom.

Do All Hydrangeas Change the Color of their Blooms?

Despite being widely known for their chameleon-like quality, not all Hydrangeas change color, even if the soil composition drastically changes. White Hydrangeas, for example, don’t contain the pigments that pink and blue Hydrangeas have.

Because of this, white Hydrangeas do not change color the way that many other varieties of blooms do naturally.

Which Kinds of Hydrangeas Change Color?

Lacecap and mophead Hydrangeas are the most common types of Hydrangea that will do the pink-blue color change. Here are some of the most common varieties of these showstoppers:

Hydrangea macrophylla – Bigleaf Hydrangeas

Blue Enchantress
Seaside Serenade (Hamptons, Cape Cod & Cape May)
Pink n Pretty
Nikko Blue
Endless Summer
Blue Prince
Hydrangea Enziandom
Big Daddy
Dear Delores

Hydrangea serrata

Tiny Tuff Stuff
Mountain Hydrangea

How Do Hydrangeas Change Color?

Since we’ve already discussed why Hydrangeas have the unique ability to change color, let’s take a look at how this happens. Unlike most colors that we see, which depend solely on the wavelengths of light that pigments absorb or reflect, Hydrangea blooms are simply a natural indicator of the soil’s pH level.

How Does Soil pH Affect a Hydrangea’s Color?

Hydrangea color shifts between red and blue, just like the pH scale. Blooms present on a continuum of color variation, from deep crimson to soft pink, to baby blue or even purple.

Source: Espoma Organic

This table shows the pH scale and how it affects the Hydrangea’s color. When the soil is more acidic (lower pH), blooms are deeper shades of blue. When the soil is more basic or alkaline (higher pH), Hydrangeas are more vibrant shades of pink.

When soil is neutral, Hydrangea blooms present as shades of purple. These are arguably the most difficult to maintain unless the soil is naturally neutral, because it requires finding the right balance without tipping the scale to one side or the other.

(For more details on growing the elusive purple Hydrangea, read on…)

pH Levels in Soil Can Change Naturally

Hydrangeas can naturally change color due to underground chemistry, such as lime leaching out of concrete from foundations, patios, or sidewalks near the shrub. Decaying materials in the surrounding soil can also change the soil’s pH.

Excessive rainfall, especially in sandy soils, can also naturally cause an increase in the soil’s pH and affect your Hydrangea’s color, as can using high-nitrogen fertilizer on nearby grass.

Monitoring the pH level in your soil is a good way to keep an eye on conditions and know if something is going on to alter the acidity of your soil.

How to Change the Color of Your Hydrangea Blooms

Knowing why and how Hydrangeas change color means that you can manipulate the soil conditions to change your Hydrangea’s blooms to your desired color. Even though the science behind the process is complicated, the practice is really easy.

You can change your Hydrangeas between pink and blue and all of the hues in between, as long as your plant is the correct type. Remember, some Hydrangeas won’t respond with color changes, so it’s important to do your research before investing time and money in your garden chemistry.

Test your soil’s pH. You can use a digital meter or a soil test kit if you’re feeling like a real scientist.
Analyze your results. Once you get your reading, determine how acidic or alkaline your soil is and if you need to raise or lower the pH.
Plan your changes. How you’ll respond to the pH level of your soil depends on your desired results.
- For blue Hydrangeas, the ideal pH is between 5.2 – 5.5.
- For pink Hydrangeas, your pH should be between 6.0 – 6.2.

How to Make Hydrangea Blooms Blue

To make your Hydrangea’s blooms turn blue, you will need to adjust your soil’s pH level so that it is between 5.2 – 5.5. You can use a soil additive or even some natural materials to increase acidity. There are many types available, like this soil acidifier.

If you’d rather go the more natural route, there are some home remedies to increase the acidity of your soil and encourage your Hydrangeas to stop blushing. Here are some of the suggestions that I found which you could try:

Vinegar
Lemon juice
Burying rusty nails (Maybe don’t try this one, unless you’re using a pot).
Citrus peels
Coffee grounds
Pine needles

Note: Some other suggestions floating around the web include burying pennies around your Hydrangea. While it may make for an exciting discovery 100 years from now, it will not make your Hydrangeas turn blue. Pennies don’t contain aluminum and won’t increase your soil’s acidity. I also wouldn’t recommend burying rusty nails, just from a safety standpoint.

Things to Consider When Turning Your Hydrangeas Blue

Some varieties of Bigleaf Hydrangeas will not turn blue, no matter how much you tinker with the pH. It’s important to research what kind of plant you have and make sure it is a color shifter.

Hydrangeas like the “Glowing Embers” will not turn true blue. According to N.C. State University’s Garden Extension, this beauty has a color range of deep “rose-red” to a burgundy-purple hue. The “Pink Elf” variety is another beauty that won’t transition to blue.

If your Hydrangea is certainly the type that should change color, and you’re still not getting the results you want, you may be lacking aluminum content.

How to Make Hydrangea Blooms Pink

To make your Hydrangea blooms pink, you will need to adjust the soil to be more alkaline, ideally with the pH level measuring around 6.0 – 6.2. If your Hydrangeas are already blue, this will involve using a soil additive such as lime.

Garden lime soil amendment is an easy, one-step soil additive that will increase the pH and allow your Hydrangea to turn pink. According to the manufacturer’s directions, you should ideally apply this at planting and reapply 2-3 times per year to maintain the desired pH. You should always retest your pH after you use a soil additive.

Things to Consider When Turning your Hydrangeas Pink

Where you live and the natural soil composition in your area will greatly impact your Hydrangea’s colors. For example, if you live in Georgia, most Hydrangeas you see will be blue because of the naturally acidic soil across the state.

If you use garden lime to make your soil more alkaline, the most effective way is to dissolve the compound in water and pour it into the soil around the base of the plant, rather than sprinkling granules onto the soil and watering. The best time to add this solution to your soil is during early spring, between April and May.

Take care not to get any of the chemical compounds or solutions on the leaves of your Hydrangea to avoid damage, and always retest your soil’s pH after applying.

How to Make Hydrangea Blooms White

White Hydrangeas are the classic beauties in your lawn or garden. These are desirable shrubs, but you will need to purchase a Hydrangea variety that naturally produces white blooms. The soil’s pH does not influence white Hydrangeas.

The best way to keep your Hydrangeas white is to keep them healthy. Blooms that go through periods of white during their life cycle will last longer when they’re getting the right amount of water, sunlight, and soil nutrients.

Also, don’t forget that your white Hydrangeas won’t be very white when they’re lying in the dirt. This is especially true for varieties like Annabelle, whose flowers are so big and heavy that they will often outweigh the strength of their stems.

For tips on preventing this issue of “legginess” in your Hydrangeas and keeping your white blooms from being covered in mud, head on over to this article on pruning and prevention.

Here are some Hydrangeas you should consider for creamy white blooms:Annabelle Hydrangea, Panicle, Incrediball, Oakleaf, Snow Queen, Snowhill, White Wedding.

How to Make Hydrangea Blooms Green

Like white Hydrangeas, green Hydrangea blooms result from nature’s processes rather than soil composition. Some start out green and change to a different color as the bloom matures and ages.

Limelight Hydrangeas produce unique creamy flowers with a hint of green that bloom late into the summer. These popular shrubs have long-lasting blooms that eventually turn pink late in the fall.

If your Hydrangea blooms turn green unexpectedly, you can probably attribute this to the plant’s natural aging process. The best way to combat this change is by ensuring that your Hydrangea is getting sufficient water, especially during the months when the temperature is higher and the sunlight levels are more intense.

Are There Purple Hydrangeas?

There aren’t many colors that are more vibrant than deep purples and violet hues on your Hydrangea. If you’ve never seen one of these beauties in person, you may be wondering if they occur naturally and how hard it is to make your Hydrangea blooms turn purple.

For purple Hydrangeas, you’ll need slightly acidic soil. It will be a balance that will take time to get just right, but once you find that perfect soil composition, you’ll be rewarded with beautiful violet blooms.

If you want to try your hand at changing your pinks and blues into pretty pops of purple for your garden, try Twist’ N Shout, Summer Lace, and Starlight Hydrangea varieties.

Some Hydrangeas tend to develop into purple hues rather than going entirely blue when the soil becomes more acidic. For the most vibrant purple Hydrangeas, try these types: Merritt Supreme, Royal Purple, Cityline Rio, Alpenglow.

Tips for Improving Your Hydrangea’s Color

While it can be challenging to change the “intensity” of your Hydrangea’s color, you can improve your blooms’ overall appearance and quality. Basic care is key to enhancing color and ensuring that your blooms stay at their peak for as long as possible.

All plants go through an aging process during their blooming season. Freshly bloomed flowers are when colors are the most vibrant, leaves are lusher, and the plant’s overall appearance is at its best.

Hydrangeas are no exception. Blooms naturally go through a process of maturing and eventually dying off, and most will go through color changes during this process.

Ensuring that your plant is getting enough light will help it produce the nutrients it needs for the best quality color. Feeding your Hydrangea with the appropriate plant food for your desired color will help to maintain the brightness throughout the life cycle.

Don’t underestimate the importance of proper watering for your Hydrangea. This is especially important if you like in an area with higher temperatures. If your Hydrangea is getting too much intense sunlight, it can cause blooms and leaves to turn brown, curl, wilt, and die off. Your Hydrangea may need more water than usual if it’s getting too much afternoon sunlight.

Watering keeps your Hydrangea’s root system cool and allows the plant to retain enough moisture to thrive.

Making Hydrangea Blooms More Vibrant

Playing with the colors of your Hydrangeas gives you the opportunity to make your blooms more vibrant. Adjusting the pH to move the color scale more toward the blue or pink side will influence the color expression on the blooms.

Beyond the chemistry, where you place your Hydrangea also impacts the intensity of the bloom’s color. Typically, if you put your Hydrangea where it gets full sun, it will have more vibrant colors. Sunlight promotes the production of more pigment in the blooms, which helps to sustain the intense color.

Hydrangeas planted in an area with too much shade cover can cause the coloration to be less vibrant, and it can also cause other problems like legginess.

What Should You Plant Near Hydrangeas?

When you’re making changes to your soil’s chemistry, you shouldn’t forget that your additives may also impact surrounding plants. Some plants may become unhealthy if the soil becomes too acidic or too alkaline. If you’re making your Hydrangeas blue, you should ensure you have other acid-loving plants nearby and the opposite for pink Hydrangeas.

Other Acid-Loving Plants to Plant Near Blue Hydrangeas

There are actually many plants that will thrive in acidic soil conditions. Here are some of the most common that you could consider for your lawn or garden.

Azaleas. These shrubs are a staple in southern states and warm areas. They are available in many different colors, so finding one to complement your blue Hydrangea should be no problem.
Rhododendrons. This is another super common shrub that grows well in many climate zones. They bloom around the same time as Hydrangeas, making for a beautiful landscape.
Daffodils. What’s not to love about this cheerful, springtime flower? These bright yellow blooms will pop up during early spring.
Camellias. These are fairly similar to Azaleas, and they produce dainty blooms during the springtime. Pink Camellias are especially lovely near blue Hydrangeas.
Marigolds. These are easy ground-cover flowers that have super cute yellow blooms. These are a go-to for most garden landscapes.
Gardenias. This sophisticated shrub is another southern staple, with gorgeous white flowers and deep green leaves. This is more of an intermediate-level plant in terms of care and maintenance.
Begonias. These are a good alternative if you’re not ready to commit to a Gardenia. Begonias are easy to grow and produce bright, colorful blooms.
Caladium. If you’re looking for a flower alternative, this is an excellent option. Caladium has large foliage in an Elephant-ear shape, with bursts of color. The green, pink, and white hues complement Hydrangeas of any shade really well, and they have a more unique look than some of the flowering options.

Alkaline-Loving Plants to Plant Near Pink Hydrangeas

If you’re going the pink bloom route with your Hydrangeas, your soil is going to be less acidic. Here are some of the best options to plant in the surrounding areas:

Lilies. These elegant beauties are a solid choice for any garden with alkaline soil, and they will continue to dazzle you year after year.
Hyacinth. These are hands-down some of my favorite flowers for right outside my house. They have a delightful fragrance and are available in a range of pastel colors that will look beautiful next to your pink Hydrangeas.
Geraniums. These petite pretties have a nice, long blooming season and are available in many shades of pink, red, and purple. Just be aware that Geraniums are very toxic for dogs and cats.
Daisies. These flowers are low-effort and low-maintenance. They have a really nice wildflower appearance and will complement the sophistication of your Hydrangeas.
Lilac. Plant these in full sun, and you’ll have a beautiful spread of flowers come springtime that will attract birds, bees, and butterflies galore.
Photinia. This is a great non-flowering option that will still give you a pop of color. These evergreen shrubs are hardy and will do well planted in-ground or in a container.
Buddleia. AKA “Blue Chip,” this miniature butterfly bush has lovely green leaves and soft lavender flowers that are low-maintenance and delicately pretty.

Putting it All Together

Changing your Hydrangea’s color can be fun and exciting, and it can give your garden a fresh, new look. If you’re going to try this at home, remember that changes won’t occur overnight.

It’s important to monitor your soil conditions and watch your plant for physical changes. It could be weeks, months, or even years before you reach your desired result.

You can also try it out on a potted Hydrangea first since the small amount of soil in a pot will be much easier to deal with than a large area outside. Happy blooming!

Why and How Hydrangeas Change Colors and What You Can Do To Influence It - RootingForBlooms.com (2024)