No-Fail Tips for Turning Hydrangeas Blue!

(photographer - unknown)

Everyone wants Blue Hydrangeas. The rarity of naturally blue flowers is an irresistible draw to gardeners. 

How to Turn Your Hydrangeas Blue?  Here are a few tips from Proven Winners:

Nikko Blue Hydrangea from Missouri Botanical garden

1. Be sure you’re working with the right kind of hydrangea.  You must have a Hydrangea macrophylla or H. serrata to have pink or blue flowers. 

(photographer -unknown)

2. Aluminum availability determines flower color. The availability of aluminum makes the flowers turn blue. Without aluminum the blooms will be pink. 

Soil pH must be low or acid (5.2-5.5) for the plant to absorb the aluminum.

from nely.bluehortensia

3. Color changes need time to take effect.  Consistent treatment is necessary to
 turn your hydrangeas blue:

  •  Plant your hydrangeas in a phosphorous-free medium, and use a phosphorus-free fertilizer with lots of potassium (i.e. 25-5-30).

  • Drench with aluminum sulfate immediately after planting. A solution of ½ oz (1 Tbsp) per gallon is a good start. Be sure the plants are well-watered before applying the aluminum sulfate as it can burn the roots. (important!!!) Drench again in 10-14 days.
  • Alternatively, you may apply a controlled-release form of aluminum sulfate. Products such as Blue-Knight® will release aluminum sulfate over a three month period. This is safer.

Some varieties shift to blue more easily than others. Here are NEW varieties which produce blue flowers more easily than others: 

(Cityline have tight sturdy stems and these maintenance free plants require no pruning for more flowers in the coming summer. Intense colors will "pop" in your garden. The flowers age quite nicely into fall as well.)

Cityline Berlin Hydrangea by Benkes Blog

 Cityline® Berlin
 Cityline® Mars
 Cityline® Venice
 Cityline® Rio
 Let’s Dance® Starlight*
 Let’s Dance® Rhapsody Blue*
 Let’s Dance® Diva!*
 Edgy™ Orbits
 Tuff Stuff™ *
 Tiny Tuff Stuff™ *

*Denotes reblooming varieties.


  1. Dear Jan the photo that you repinned from Beverly Russell is actually my photograph. I can attest to the fact that nothing ever has been added to the soil in this garden. They are the best and happiest of any blue hydrangeas I have ever seen-and I have no idea why. Best, Deborah

    1. Deborah - I am so sorry! and I have changed the caption to your name. And I have added your fabulous website there too - Love your work!

    2. Jan, not to worry-the attribution of pictures on Pinterest get muddled the more they get passed around. But I do appreciate your setting the record straight. The most amazing thing is the blue hydrangeas. They have never been treated with anything. Deborah

    3. My mother lived in the coastal mountains of norther Calif. and her Hydrangas were a beautiful blue. She said her soil was very acidity living among the Redwoods

  2. This is a wonderful tip about having blue hydrangeas. I finally planted a hydrangea, a small type (Paniculata I think) called Bombshell, so that type won't turn blue. Still, it is my only hydrangea and I wanted a smaller bush so I am happy with it.

  3. I particularly like the title of your blog Serenity in the Garden. your website is amazing and always bring me interesting informations and ideas to deal with thanks.

  4. I just discovered your site and I am thrilled with the serene kids and great gardening tips. Thanks

  5. Blue hydrangeas are amazing. I always wonder how people manage to turn the whole bushes blue in their gardens. I had so much trouble even with a small pot. My experience is pretty interesting, however.

    I actually bought a blue hydrangea. Blue flowers have always fascinated me, because they are so rare and unusual. As soon as I saw that plant, it had to be mine. I thought it was naturally blue and would always stay that way.

    When it bloomed the following year, I was in for a big disappointment. The flowers were pink!

    Then I got on the Internet and looked for the explanation. Apparently, hydrangeas were able to change colour according to the type of soil.

    My family and friends gave me all kinds of advice how to make them blue: put some aluminium nails in the soil, or coffee grounds, or vinegar... but nothing worked.

    Then I found a special product in a flower shop. Adding that to the soil was supposed to make my hydrangeas blue. I started adding it according to the instructions, but it obviously wasn't enough, because they bloomed in pink again. Then I added a large quantity at once and that burned my hydrangeas.

    The following spring my mother was pruning some plants in our garden and accidentally cut the parts of my hydrangea where the blossoms were supposed to form, so it didn't bloom at all that year. I was very sad, because my chance to try to make it blue was ruined again.

    Finally, the third year I started adding that product to the soil early and in larger quantities, but increased it gradually. And indeed, when my hydrangea bloomed, it had awesome blue flowers. They did turn more purple during the summer, though.


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