Hydrangea blues that is!
Hydrangeas are my favorite flower and shrub, a passion I inherited from my mother! And while I am fine with the traditional blue, as I expand my hydrangea landscape, I’ve attempted to introduce some other colors, such as whites and limelights (successful) and pinks (unsuccessful).
With varying degrees of intensity of hue, most of my hydrangeas are blue!
My lack of pink hues in my macrophylla hydrangea collection reminds me of a close friend whose first four children were boys. When she became pregnant a fifth time, she decided to wear only pink for the entire pregnancy! In her first trimester she was told to expect twins. She adored her sons, but I think the trains, trucks, footballs, baseball bats and dinosaur decor had run its course. She wanted that pop of pink! She wanted to introduce Barbie to Spiderman! But, what popped out were fraternal twins-two adorable baby boys! She was delighted. She was in love. Her passion for pink did not linger. She saved a fortune on baby clothes and toys, and she’ll certainly save a fortune on weddings!
But I empathize with her when it comes to my blue hydrangea children. I adore their show-off blue audaciousness and rock-steady performances. Although I turn to other flowers to contribute pinks, roses and magenta hues in my landscape, I must confess: I too, yearn for that pop of pink in my macrophylla hydrangea family!
The failure in pink is all about my soil chemistry. Here along the Delaware coast, USDA Zone 7b, my soil has a good deal of aluminum sulfate composition and as a result my pink purchases eventually turn into blue boasters! And I am fine with that! But I keep trying, thinking my soil’s chemistry will change all by itself.
I fell in love with a particular hydrangea below (left). Its old-fashioned look and combination of pink centers and creamy white edges reminded me of something my grandmothers might have selected. I quickly scooped it up in my garden center cart and made a bee-line to the checkout counter. I planted it in a special location–at my garden gate entrance where my visitors and I would not miss this unique greeting. For the remainder of the summer I enjoyed the variegated pink display. It was a great choice as the official welcome hostess to my garden. I looked forward to it growing profusely offering delicate pinky goodness in my landscape and bouquets! I believe this is Forever and Ever “Peppermint” though I lost the tag on it when I bought it.
I should not have been surprised, but I was, that my soil had a different plan in store for that shrub. The following year not a trace of pink remained. The blue bully lurking in my soil battled for dominance and won, replacing all of the original, dainty pink hues. To the victor goes the spoils! I am a gracious loser!
While the colors of some hydrangeas varieties are affected by pH, that is not the only factor. Your soil’s pH will affect the uptake of nutrients and minerals that pre-exist in the soil. With hydrangeas, it is the uptake of aluminum sulfate that is the primary factor for color.
If you have pink, and want blue, it’s easy to add aluminum sulfate to the soil if it is not there, and make your soil more acidic.
But if aluminum sulfate is already in your soil naturally, it’s much more difficult to remove, and simply changing the pH toward alkaline will only slow down the plant’s ability to access that aluminum. But it will not be enough to override the blue. This Georgia Extension site explains it. A good deal of misinformation and Old Wives’ Tales on changing color abound on the Internet. My mom told me pushing pennies in the soil would change, or boost the color!
Another way to explain how it works is to think of your soil pH as a straw. Acidic soil would be a very wide straw, allowing the plant to uptake its mineral needs, and therefore turning pink into blues or purples or violets. Alkaline soil would be akin to a very narrow straw, preventing the plant from accessing those same minerals, therefore remaining pink. If the aluminum sulfate and other minerals are already in the soil, it’s easy to change the size of the straw. But those minerals have to be there, or be added. It is next to impossible to remove minerals, which is what one needs to do to get the pink hues. But you can try to reduce access to those minerals by narrowing the straw.
Adding commercial additives like aluminum sulfate or acidifier however, will not be reliably stable. We all know hydrangeas love water, and if we are not getting enough rain, we are watering often! This helps wash away what we are adding to the soil. The water pushes these nutrients through the soil profile, so the desired change is rarely permanent. If your soil is healthy to begin with, soil with a lot of organic matter, the minerals will have something to hang on to.
When planting a new pink hydrangea that you hope to shift to blue, it is good to amend the soil at the very beginning, adding compost, leaf litter, pine straw etc., which take longer to decompose, and while doing so alters the soil’s composition and quality.
Some soils have pockets of alkaline and acidic qualities. Rarely is your soil consistent across your property. Soils with a diverse composition,combined with an unknown history can yield surprising results! Did a structure exist on the spot sometime in the recent or distant past? Did the original roofer leave beer cans that got covered over? Are there decaying roots from a plant that existed decades ago? Factors like that might account for a pH or metallic anomaly. Neutral pH can be a delightful blessing, providing the hydrangea owner with blues, pinks and purples from the same plant! Roots spread in all directions so who knows what they’ve tapped into!
The plants I buy purposely as blue are normally not as beautiful as the blues that start out as pink and transition over to blue. Those chameleon blues are stunners! The flower below, was a deep pink, hot-house hydrangeas with blooms forced for the Easter market. I planted it that same year and it stopped blooming, which I expected. For an additional two years it grew and leafed out and did not bloom. But on the third planted year, the shrub, nearly 5 foot tall, was festooned with these beautiful blue balls with just a whisper hint of lavender! Why its more blue than any of the blues I bought as blue!
In July 2017, I bought another hydrangea (because one can never have enough and I am completely justified since I suffer from GBTH (Gotta Buy This Hydrangea) Syndrome–a serious affliction for which I am refusing treatment! My husband, however, has tried many forms of intervention upon me, alas (hooray) to no avail. I googly-eyed and exclaimed “ooh la la” over a specimen and eventually bought the “Merritt’s Supreme” looker, seen below. The garden center owner assured me it “should stay” pink. Even without this expert assurance, I was going to buy this showy darling! I heaved her into my trunk for the short ride home (yes, I refer to it as a she). Here it is where I gave her a new home in a wooded setting:
Miss Merritt is leafing out now and setting her 2018 buds. Other than adding home-grown compost at planting, I’ve not added any fertilizer or amendments. I resolved to let nature take her course. Stay tuned for the June reveal!
UPDATE: June 17, 2018: We’ve gone purple! I love the color shift.
In 2018 I don’t have as many blooms. The spot I selected clearly gets more shade than what my Merritt’s Supreme obtained at her nursery. We’re going to do some strategic tree pruning, and take down one Arborvitae that is not doing well, and that should allow more light to filter through and improve the flower yield of this shrub for 2019. But look at this violet color!
Update 2021: In the past three years my Merritt Supreme has grown quite a bit. It really needs three years to adjust to its new environment and come into its own. The color has remained a violet purple. You can see a true blue in the background:
As new cultivars get introduced to the market, and breeding and genetics become more sophisticated, I find that certain cultivars possess strong genetic colorfastness. In an other more wooded area of my yard, I purchased an Endless Summer “Summer Crush” in late summer of 2020. The fading blooms were pink, as was the beautiful photo on the label. It was a late season deal, so I wasn’t going to see any new blossoms after planting.
But this spring she began to leaf out and as the green buds expanded, I received the pink I’ve always longed for. Here is the display after its first year in the ground:
Despite being surrounded by blue hydrangeas, tree droppings, pine needles, and leaf litter, this baby has not shifted color in the least. I know aluminum sulfate is in the soil, but it doesn’t seem to matter. Time will tell as the roots expand into the the surrounding soil.
Another hydrangea I bought from Wayside Gardens (about 10 years ago) is “Pistachio”. The color of the genetics is steady and unwavering. This is the color advertised, the color I received with its first, measly single bloom, and the blooms I enjoy 10 years later!
Obviously, tenacity, patience and experimentation has broken through my blue barrier! I am very fortunate to work with Cooperative Extension experts, agents and specialists, and through them, I appreciate the value of soil tests, understanding how soils, and the micronutrients contained within, work to feed a plant.
Get to know your soil before listening to your neighbor or reading a social media post for a solution. It is important to know basic soil chemistry, the role of organic matter for healthy soil, and what your shrub needs rather than what you want it to be.
For a hydrangea to reach its full color potential within its own color spectrum also means you must provide it with a happy home. The right plant in the right spot. The right shrub in the wrong spot will not perform as it should. Too much sun, too much heat, improper pruning, stone mulch, are all human errors that can stress your hydrangea. If you are in the U.S., contact a Cooperative Extension expert or Master Gardener. Very likely there is one in every county that can respond to your specific needs — experts who understand your local climate and soil.