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Hydrangea's Colors Can Please Gardeners
By Norman Winter
Central Mississippi Research & Extension Center
It is remarkable when a plant performs equally well in soils that are acidic or alkaline. It is even more wonderful when that plant has large pink flowers in soils with the higher pH and blue blossoms in the soils with the lower pH.
I am referring to the big leaf hydrangea, and it is putting on a show now across the South. No other plant seems to garner as many questions on flower color, propagation and drying. And no plant can reap the frustrations as does a hydrangea should it fail to bloom once in 30 years.
The hydrangea made its way to the United States during the 1800s and is loved throughout the South. Though called the French hydrangea, it is really from Japan. The French did a little tweaking and somehow came to be known as the originators.
The big leaf hydrangea has mophead-shaped flowers that can defy logic with their size. They are also offered in what many connoisseurs of hydrangeas consider the cream of the crop, the lacecap forms.
The lacecap hydrangea is as beautiful as the mophead, but not as popular. It should be, but lack of consumer education may be the culprit. Many gardeners think something has gone wrong when their hydrangea blooms and they find they bought a lacecap instead of a mophead.
In the South, hydrangeas prefer morning sun and afternoon shade in a rich, organic-amended soil followed by a good layer of mulch. When the plants are growing and producing flowers, do not let the soil dry to the point of wilting the leaves. Feed throughout the growing season with several light applications of a complete and balanced fertilizer such as a 8-8-8.
I grew up in Texas where the hydrangea blossoms are hot pink and was astounded at seeing my first ones in the Southeast that were blue. Both are beautiful, including those that are kind of purple, which indicates the soil has a neutral pH.
It seems gardeners always want the opposite of what they have, so here is how it works. Flower color is related to the aluminum available to the plant. Aluminum is available in acidic soils and the flowers are blue. In alkaline soils, aluminum is not available, and the flowers are pink.
So if you want pink flowers next year, modify your pH by watering into the soil dolomite limestone at a rate of about 1 cup per 10 square feet. If yours are pink and you want blue, water in 1/2 cup of wettable sulfur per 10 square feet. This is not an exact formula as your soils may be at extreme pH levels. If this is the case, a soil test will come in mighty handy.
Gardeners who incorrectly prune hydrangeas can seriously hurt next year's flower production. Prune when the flowers begin to fade. Deadhead flowers and cut back as needed to make your plants bushy. Flower buds for next year will begin to form in late summer. Pruning in late winter is not recommended because it will eliminate many of these flower buds.
This time of year, the biggest question I have from gardeners is how to cut and dry the hydrangea flower for arrangements. I will admit I have not tried to dry the first one yet.
There are probably several methods that work, but what I know for a fact is that Mrs. Polly Roberts of Mount Olive, and now of Brandon, does it without any failures. She has tried many methods, and this is the one that works for her.
She cuts the blooms after they have started to age and places them in a large vase of water. She keeps the vase filled with water until the flowers themselves have dried. Her color retention is good and the flowers last for years.