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How to Change Hydrangea Flowers From Pink to Blue (or Vice Versa)

Published on May 16, 2023 โ™› By Melissa J. Will

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While it’s not possible for most hydrangeas, certain varieties can shift from pink to blue (or vice versa) with the right soil conditions and these tips.

Not sure what type you are growing? See How to Identify Your Hydrangea to figure it out.

Pink and blue hydrangea flowers.

How to Change Hydrangea Bloom Colors

Blue and pink hydrangea flowers.

Can you change the color of hydrangea flowers from pink to blue or blue to pink?

It’s a common misconception that all hydrangeas can change colors. They cannot. And the ones that can shift from pink to blue or blue to pink require the right timing and conditions.

  • The hydrangeas that can shift colors include some Bigleaf hydrangeas (Hydrangea macrophylla) and Mountain hydrangeas (Hydrangea serrata) varieties. You can see pictures of them below.
  • With those varieties, start with plants with medium or light pink or blue flower color values.
    • Deep red and blue colors will not change. White and green flowers will not change.
  • To work, you will adjust the soil pH level and control the availability of aluminum in the soil. There is more on this below.
  • For long-term results, this mean growing the hydrangea in a container where you can control the soil conditions ongoing, not in the ground.
  • Following these tips, your hydrangea flowers (known as sepals) will gradually change color.
  • It may take a year or more depending on the original soil pH level.
  • Also, itโ€™s easier to shift pink flowers to blue than blue to pink.

Contents

  • Hydrangeas That Can Change Color
  • Hydrangea Garden Myths
  • Hydrangea Color pH Chart
  • How to Turn Pink Hydrangeas Blue
  • How to Turn Blue Hydrangeas Pink
  • Frequently Asked Questions
  • Resources

Hydrangeas That Can Change Color

Big Leaf Hydrangea

Hydrangea macrophylla.

Hydrangea macrophylla

Light pink, purple, or blue varieties only.

Also known as ๏ฌ‚oristโ€™s hydrangea, hortensia, mophead, French, or lacecap.

โ€ข Hardy to USDA zone 5
โ€ข Bloom on old wood: do not prune, protect in winter

Proven Winnersยฎ varieties include:
Abracadabraยฎ series, Citylineยฎ series, Edgyยฎ series, Letโ€™s Danceยฎ series, Parapluโ„ข

Mountain Hydrangea

Hydrangea serrata.

Hydrangea serrata

Light pink, purple, or blue varieties only.

โ€ข Hardy to USDA zone 5
โ€ข Bloom on old wood: do not prune

Proven Winnersยฎ varieties include: Tuff Stuffโ„ข series


Hydrangea Garden Myths

Penny coin
Penny coin

There are plenty of myths about changing hydrangea flower colors.

Some of these include burying pennies or rusty metal in the soil, or adding pine needles, coffee grounds, Epsom salt, vinegar, or aluminum foil near a hydrangea plant.

Spoiler Alert: none of these work.

See Popular Garden Myths We Have All Fallen For for more (popular) garden misinformation and folklore.


Hydrangea Color pH Chart

Hydrangea flowers changing from blue to pink.

Hydrangea Color pH Chart

Only Bigleaf / Mophead (Hydrangea macrophylla) and Mountain (Hydrangea serrata) hydrangeas can shift color in response to changes in soil pH.

Blue flowerspH 5.5 or lowerAluminum available
Purple flowerspH 5.5 to 6.5Some aluminum available
Pink flowerspH 6.5 or higherNo aluminium available

How to Turn Pink Hydrangeas Blue

To make the change from pink to blue, grow the plant in a container and lower the soil pH level to 5.6 by adding aluminum sulfate.

Choose the Right Type of Hydrangea

Start with Bigleaf (H. macrophylla) or Mountain (H. serrata) hydrangeas with medium or light pink, purple, or blue flowers.

Grow in a Container

Grow the hydrangea in a container. This makes it much easier to control the growing conditions long-term. Trying to change the pH of garden soil is a lifelong battle and not worth the effort.

Use Good Potting Mix

Use a good commercial potting mix suitable for shrubs and a low phosphorus-high potassium fertilizer (25-5-30), otherwise the phosphorus will lock up the aluminum.

Monitor Your Soil pH Level

Measure your soil pH level to gauge where you’re at and how long it may take. It’s a gradual process and you can’t push it without harming the plant. At 5.6 or lower, the shift to blue becomes visible.

Options: use test strips like these ones: Garden Tutor Soil pH Test Strips. Another brand is Fisherbrand Plastic pH Indicator Strips.

If growing in the ground (not recommended because results are not sustainable), another option is to contact your  local university extension office or lab that does soil tests to find out the known range for your areas or lookup aerial pH maps.

You could also use physical clues: if hydrangeas stay blue in your garden, that’s a good indication the soil pH is right where you want it.

Add Aluminum Sulfate If Needed

Water the plant deeply (to avoid burning roots with next step) and then apply an application of aluminum sulfate Al2(SO4)3, also called powdered alum, following the product instructions.

You can find this online or at a plant nursery. There are also similar products for this purpose at plant nurseries: Color Me Blue or Color Me Pink.

The sulphur (sulfate) will bring the pH level down, making the aluminum available to the plant but it is a slow process taking months or longer.

Your product should have instructions. Otherwise, do this:

  • For longest lasting-results, use a half-application (e.g. 1.5 teaspoons aluminium sulfate in one gallon of water) in fall and again at bud break in spring.
  • Repeat annually as needed.
  • Always check the package for precautions and instructions.

Alternately you can do just one application per year.

Either way, more is not better: too much aluminum will kill the plant. And each plant has a limit to how blue it will get.

Take Photos to Monitor Changes

Photograph your plant at the start or match the color to paint chip and check progress over the next year.

Once the pH level is lower than 5.6, the color change becomes visible.


How to Turn Blue Hydrangeas Pink

To change flowers from blue to pink, grow the plant in a container and make the soil pH more alkaline by adding garden lime (calcium hydroxide, Ca(OH)2). Your product should have instructions for correct application amounts.

This will stop the plantโ€™s ability to absorb any aluminum present. Without aluminum, the color shifts to pink.

  • Pink= Aluminium not available / alkaline pH level (6.5 or higher).
  • Purple = Some aluminum available + pH between 5.5 and 6.5.
  • Blue Flowers = Aluminium present + acidic pH level (5.5 or lower).

Frequently Asked Questions

How long does it take hydrangeas to change color?

Not all hydrangeas can change color but the flowers that do can take a year to shift from pink to blue or blue to pink.

Which hydrangeas can change flower color?

Two varieties can change color if conditions are right. These are Hydrangea macrophylla, also known as Big Leaf or Mophead hydrangeas, as well as Mountain hydrangea (Hydrangea serrata).

Can you change the color of hydrangeas by putting copper pennies in the soil?

No, you cannot change the color of hydrangea flowers by putting pennies or any other metals in the soil. This is an old garden myth.

Can you change soil pH using pine needles?

No. Any effect on soil pH from pine needles is temporary. This explains why pine needles are not effective for changing soil pH long-term.

What is the right soil pH level for blue hydrangeas?

Blue hydrangeas need a soil pH of 5.5 or lower (acidic soil) with aluminum available in the soil.

What is the right soil pH level for purple hydrangeas?

Hydrangeas are light purple, a combination of pink and blue, when soil pH levels are between 5.5 and 6.5 and some aluminum is available.

What is the right soil pH level for pink hydrangeas?

Pink hydrangeas need soil pH of 6.5 or higher (alkaline soil) with no aluminum available.

How do you change pink Mophead hydrangeas blue?

Changing hydrangeas from pink to blue requires lowering the soil pH level to 5.5 or lower using aluminum sulfate.

How do you change blue hydrangeas to pink?

Some hydrangeas can change from blue to pink by making the soil pH more alkaline (6.5 or higher) using garden lime (calcium hydroxide).


Resources

Hydrangea | Genus: Hydrangea

Blue hydrangea flower.

Flowering plants native to Asia and Americas
โ€ข Hardiness Zones vary from 3 to 9
โ€ข Morning and part sun
โ€ข Soil: does not like to dry out
โ€ข Fertilizer: Holly-tone by Espoma in spring only if required.
โ€ข Propagation: How to Root Hydrangea Cuttings
โ€ข Pruning: Need to prune depends on variety
โ€ข Pink/Blue: See how color changes

  • Hydrangea Growing Tips

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Hydrangea Pruning Tips

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Pruning and deadheading hydrangea shrubs.
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Read More

  • Role of aluminum in red-to-blue color changes in Hydrangea macrophylla sepals
  • Proven Winners – Blue Hydrangeas
  • Proven Winners – Hydrangeas Demystified
  • Soil Acidification: How to Lower Soil pH

It’s an interesting plant! Let me know how your color change goes.

~Melissa the Empress of Dirt โ™›

Blue and pink hydrangea flowers.
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How to Change Hydrangea Flowers From Pink To Blue

Tips for gradually changing light pink Bigleaf (Hydrangea macrophylla)ย and Mountain (Hydrangea serrata) from pink to blue.
Prep Time20 minutes mins
Steps20 minutes mins
Total Time40 minutes mins
Author: Melissa J. Will
Cost: $35.00

Equipment

  • Soil pH Test Strips
  • Potting mix
  • Aluminum Sulfate

Supplies & Materials

  • 1 shrub Hydrangea Bigleaf or Mountain
  • 1 bag Aluminum Sulfate

Instructions

  • Plant hydrangea in container with suitable potting mix.
    1 shrub Hydrangea
  • Test soil pH and record value.
  • Take photos of any flowers that form from now onward.
  • In fall, water plant thoroughly then apply half dose of aluminum sulfate per product instructions (usually 1.5 teaspoon in 1 gallon water).
    1 bag Aluminum Sulfate
  • Overwinter plant as needed to protect from freezing temperatures.
  • In spring, at bud break, apply another half dose of aluminum sulfate.
  • Measure soil pH every few months and compare.
  • When pH is 5.6 or lower, hydrangeas can take up aluminum in soil and gradually turn light blue.

Notes

For instructions on turning light blue flowers to pink, see https://empressofdirt.net/change-hydrangea-colors/
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Blue and pink hydrangea flowers.
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Comments

  1. Claire Daniel says

    February 24, 2024 at 1:55 pm

    Thank you so much.

    Reply
  2. Mary Lou Mayfield says

    November 12, 2021 at 6:39 am

    Because I live between zone 4 and 5, I have to cover my bigleaf Hydrangea in the fall. This requires cutting it back, which you do not recommend. What do you suggest?

    Reply
    • Melissa J. Will says

      November 12, 2021 at 7:51 pm

      Is this your first year with it or has it already survived previous winters? I would not cut it back. I would insulate it with something like straw or leaves secured in place with burlap.

      Reply

Melissa J. Will - Empress of DirtWelcome!
I’m Melissa J. Will a.k.a. the Empress of Dirt (Ontario, Canada).
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