Them Old Hydrangea Blues

August 15, 2008 | By | Comments (8)

Q: I have a common question concerning my hydrangeas blooming pink instead of blue. I purchased them while they were blooming and they were blue.
I know it is all about the soil — acid for blue blooms — I have watered them with aluminum sulfate — and they continue to bloom light pink.

Question 1 — Am I using the correct product — if so, how often do I water with this and when do I begin?
Quesion 2 — When do I prune my hydrangeas so I can be assured of blooms the following year?

Thanks for you time and I look forward to hearing from you.

A: Hi Lavonda,

Because your hydrangeas were blooming blue when you bought them and have now turned pink, I would guess you have somewhat alkaline soil. Making the soil acid will take time. You probably won’t see a difference this year. Repeat the applications of aluminum sulfate a couple of more times, but don’t overdo it, because too much aluminum in the soil isn’t good for plants. You could also apply garden sulfur to the soil surface around your plants and water it in. And if you’re a ground coffee drinker, save the grounds and spread them on the soil around your plants to acidify it. Once your hydrangeas start blooming blue, you may have to repeat the application of sulfur every couple of years to keep them that way.

As for pruning, for most varieties, the rule is prune them immediately after their flowers fade. This is because most bloom on growth made the previous year. So if you prune them in fall, winter, or spring, you’ll cut off the flower buds. However, a few types, such as ‘Endless Summer,’ ‘All Summer Beauty,’ and ‘Penny Mac,’ bloom on both last year’s growth and new growth. So even if you prune them to the ground in winter, you’ll still get blooms.

Shout-Out to Readers: What trick do you use to turn hydrangeas blue or pink? Be nice and tell us.


  1. Grumpy

    It’s hard to give you a definite answer without knowing what kind of hydrangeas you have. But when hydrangeas fail to bloom, usually one or more of the following factors are behind it.
    1. Lack of sun. Since yours get plenty of sun, we can discount this one.
    2. Pruning at the wrong time. Some hydrangeas, such as ‘Annabelle,’ ‘Limelight,’ and ‘Pee Gee,’ bloom on new growth. This means you prune them in winter or early spring. Oakleaf and most kinds of French hydrangeas (the ones with blue or pink flowers) bloom on growth made the previous year. If you prune them in fall, winter, or spring, you’ll get very few flowers. Prune them as soon as their flowers fade.
    3. Late spring freezes can kill flower buds on oakleaf and French hydrangeas and ruin the bloom.

    August 31, 2008 at 9:40 am
  2. jean b.

    We moved into a new house 5 years ago. We planted 5 hydrangeas(not sure what kind) and also planted 3 Oak leaf hydranges. The oakleaf have bloomed for two years, but the others have not bloomed. Healthy plants and get full sun. What can I do to get them to bloom?

    August 30, 2008 at 9:32 pm
  3. Grumpy

    Nikki, I concur. Many folks don’t know French hydrangea (Hydrangea macrophylla) can be white as well as blue or pink. Thanks for helping out Sylvia. If more readers would do likewise, the Grump’s job would be so much easier.

    August 22, 2008 at 5:06 pm
  4. nikkipolani

    Sylvia, you may have the kind of hydrangeas that don’t turn pink or blue. I bought some (Mme Emile Mouliere) on purpose for my white-flowering front garden. The blooms start out greenish and eventually white.

    August 22, 2008 at 2:28 pm
  5. Sylvia

    The blooms on my hydrangea are light green, not blue or red. I’ve added aluminum sulfate a couple of times to the soil and still no color. Why??
    They do get plenty of water and sun.

    August 22, 2008 at 2:00 pm
  6. Grumpy

    When blue or pink hydrangeas fail to bloom, the cause is usually one of two reasons.
    1. Lack of sun. Hydrangeas need lots of water in the summer. When they wilt, people think it means they need shade. Wrong. Hydrangeas in shade have nice, pretty leaves and few if any flowers.
    2. Pruning at the wrong time. Some newer kinds, such as ‘Endless Summer’ and ‘Pennymac,’ bloom on new growth, so you can prune them in spring, fall, or winter and still get summer blooms. Most types, however, such as ‘Nikko Blue,’ bloom on growth made the previous year. If you prune them in spring, fall, or winter, you’ll cut off most of the flower buds. For these types, it’s best to prune only those branches that flower directly after the flowers fade.
    Don’t know what kind of hydrangea you have? Follow the advice for ‘Nikko Blue.’

    August 20, 2008 at 10:07 am
  7. Stefanie

    What if the hydrangea plants did not bloom at all, just big beautiful leaves. When is the correct time to prune them??

    August 20, 2008 at 9:16 am
  8. Nancy Bond

    Beautiful in any color!

    August 15, 2008 at 4:38 pm

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