How To Keep Red Color In Red 'n Pretty Hydrangea - Knowledgebase Question

Temecula, CA
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Question by djbixler
March 30, 2001
I know that by adding aluminum sulfate, you can turn or keep some hydrangeas blue. Is there anything I need to add to my soil to keep my Red 'n Pretty hydrangea red or to intensify the red? I just planted one in my camellia/azalea bed which has been amended several times with lots of peat. This bed is also mulched every winter with pine needles from our Christmas tree. The pine needles are turned into the soil every Jan. when we cut up the new tree for mulch. I haven't done a soil test, but I believe that this has created somewhat acidic soil since my camellias and azaleas thrive in this location. By the way, can I expect to see flowers this summer or do hydrangeas need longer to establish themselves before flowering? Thank you!!!! Janette

Avatar for Infiniteheal
A comment from Infiniteheal
June 23, 2018
Iron is what keeps your hydrangeas in the red zone. My grandmother would take some big 6" iron nails and hammer 6-10 of them around the outside of the root zone to keep her's in color. I've done the same and it works! You can always purchase iron sulfate or use other more natural iron rich nutrients like blood meal to do the trick. If you want to add blue, then aluminum is the key. The DIY aluminum trick is crunching up a long snake of aluminum foil and laying it 2 inches down in the soil just outside the root zone. It takes a bit longer than aluminum sulfate powder you can buy but it lasts longer. The powder amendment washes out more quickly.

Answer from NGA
March 30, 2001
Hydrangea blooms color can be affected by soil pH. A somewhat acidic 5.5 should turn them blue, a more alkaline 6.0 should turn them pink with the effect being more intense the more extreme the pH. Pink and red hydrangeas often turn blue or purple in acid soils. Blue hydrangeas can turn pink in alkaline soils. Plants can be made (or kept) blue by applying aluminum sulfate to the soil; plants can be kept pink by liming the soil or applying superphosphate. Because you've added peat and pine needles to your soil, the pH will be on the acidic side. Do a soil test and add lime if necessary to sweeten the soil. It's best to apply amendments in February or March of each year so the blossoms will be the color you expect!

Your hydrangea will probably bloom this year (they don't take long to become established!) Enjoy!

Homewood, IL
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Answer from somewhereinillinois
June 23, 2018
I had never heard of this particular hydrangea so I googled it to see an image of it. Wow!!! That color is very beautiful. I did notice that Monrovia suggested azalea, camellia, and hosta as companion plants so I am going to hazard a guess that an acidic soil should be fine to maintain the color you like. More likely consistent moisture is the key for this one?

Regarding blooming, I planted six small Little Limes I received from Bluestone Perennials in my beds this year and one has grown significantly and is blooming. They are about a foot to 18 inches tall but blooms they have. Mine are paniculatas so this may be different for macrophyllas.

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Answer from Jackie_Trouard
June 23, 2018
Thumb of 2018-06-23/Jackie_Trouard/d61277

I purchased this hydrangea thinking it was white; however I used a big box store soil and it has bloomed more purple/pink. the older the blooms have gotten the more purple is becomes. I think I'll follow the above advise and keep it in the purple/pink zone. Appreciate being a (new) member of this group.

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