Blue Hydrangeas

June 23rd, 2010

This year I put some aluminum sulfate on the dirt around my hydrangeas to get a blue bloom.  I don’t do this every year because I have mixed feelings about gigantic blue blossoms.  I think they look a little goofy… a little clownish… a little bit like cotton candy at the fair.

Did you know that the best way to get blue blooms on a hydrangea is to plant one beside a house with a slate roof?  Rainwater that comes off of a slate roof contains mild doses of sulfuric acid that won’t damage a hydrangea’s roots, but will result in a nice blue flower.  Most people might find adding a slate roof to their homes for the sake of blue hydrangeas to be a bit beyond their budget so they can choose the more budget friendly option of sprinkling on a bit of aluminum sulfate.  Just be careful and maybe only add it to the soil every other year.  Give your amended hydrangeas plenty of water too, as aluminum sulfate is acid and well… need I say more?  Acid… roots… plants… these things must exist in a delicate balance.

And as goofy as the big blue blooms look to me on a shrub…

They are absolutely lovely in an arrangement on the kitchen table.


  • Kait:

    I absolutely love hydrangeas. They grow like weeds in almost every yard in my neighbourhood. All the colours of the rainbow and then some. BUT when I was a kid my sister lived in a icky old house that had a graveyard practically right outside the back door. The front of her house had huge dark hedges and a couple of purplish-blue hydrangeas. I had the absolute creeps from her house, backyard and creepy ass hydrangeas to make me dislike them for years.

  • kimj:


  • Diane:

    Lovely blue/purple blooms. Rther than get the “Endless Summer” I got it’s cousin “Forever & Ever” from Lowe’s. It is on its 4th year now and is simply gorgeous this year. The prettiest deep blue/purple. I was thinking of cutting some to fill a pottery pitcher that I have and your picture has convinced me to do so tonight. Mine started out (from the store) as pink, but in my GA acidic clay it’s blue. I believe it is lime that I would need to add to get it back to pink and I toy with the idea from time to time but in the end let Mother Nature have her way.

    Thanks for the inspiration to being some of the lovelies inside!

  • M.R.:

    Excuse me? You said that you had a depressing story about blue hydrangeas. Did I come to the wrong web page? This is a story of delightful blue hydrangeas!

  • priscilla:

    I had never heard about the slate roof/blue hydrangea connection. I have 1920′s colonial with the original slate roof and mine are bright blue!

  • Rechelle:

    M.R. – Perhaps it was I who was depressed and not the hydrangeas! Fortunately, their big old blooms lifted my spirits!

  • I love to hear all about hydrangeas. I want to grow them all over my small yard. My Mom and I just bought another one today. Thanks for the post.


  • nanne:

    hi rechelle!

    gorgeous hydrangeas!! i’m a recent transplant (from alabama) to the midwest & am slowly learning about zone 5 gardening –it gets freakin’ cold here in indiana!!!. would love to know what kind of hydrangeas you have had success with…


  • I love the blue flowers, but my sister is like you and thinks they are weird. I may have to sneak some sluminum sulfate in the soil for next year! When would be the best time to add this to the soil, in the winter?


    PS – I loved the book, “Me Talk Pretty One Day”. Very interesting read.