How to Turn Your Mopheads Blue


Shannon O'DonnellI spend much of my free time gardening (which isn’t often now with one toddler and another baby quickly on the way!), and I’m crazy about all kinds of flowers: showy lavender lilacs, weepy wisteria, wonderfully fragrant hyacinths. But my absolute favorite of the bunch, hands down, is the hydrangea. I’m just mad over the huge, old-fashioned, moppy blue blooms of a giant hydrangea bush. The key descriptive there though, for me anyway, is the BLUE part!

I grew up in the Seattle area, and these soft blue and lavender explosions of color are seen in yard after yard all spring and summer around Puget Sound. When our family moved to the Bay Area, we received several ‘housewarming hydrangeas’ from friends and relatives who knew they were my favorite flower. I eagerly planted about 10 of them around my yard last spring, in an attempt to fill my yard with those memories of home.

Last year upon planting, the blooms all stayed their soothing shade of blue. However, spring has sprung once again here in California, and my hydrangeas, just now beginning to flower, are sporting a rather garish shade of hot pink! Not that I don’t like pink (as you may have noticed from my predominantly pink wardrobe), but I just really adore that soft, periwinkle blue of hydrangeas, and was disappointed to see the color changing in my garden.

Not that I can’t change them back to their original shade…I’ll just have to wait another year. Whether you like your hydrangeas dressed in fuchsia or cornflower, there IS a way to achieve and maintain your hue of choice. It’s all about the pH of your soil. Pink hydrangeas will stay that way for you in a more alkaline (basic) dirt, while the blue blooms that I prefer need a surrounding that is higher in acidity. I think that much of the soil around San Francisco leans basic, as the majority of the blooms I see coming in around the Bay Area are in pink.

So here is the recipe for (trying anyway!) to turn your mopheads blue:

* Add some aluminum sulfate (found in any garden center) to the soil surrounding your hydrangea plants. Begin in the late winter/early spring (before the blooms have begun to show), and keep it up through the growing season. You should use 1 Tablespoon of aluminum sulfate per one gallon of water, probably at least once a week. Be careful not too over-do it or you may burn the roots of your plant!

* You can also lower the pH of the soil around your hydrangeas by mixing in organic matter that is naturally high in acidity, such as coffee grounds or citrus peels.

* Be sure to use a fertilizer that is LOW in phosphates and high in potassium. Avoid phosphorus, as it blocks the aluminum from getting into the hydrangea plant…the availability of aluminum to the bush is what will keep that nice blue shade going for you all season long.

Happy Spring Gardening!

Shannon O’Donnell
NBC11 WeatherPlus Meteorologist


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