This handsome blue hydrangea is a fine plant for permanence if you are fortunate enough to find a supply source.
It is a native shrub of Japan and has found favor in some places in the warmer parts of southern New England and Long Island.
Characteristics Hydrangeas
It is not hard in Boston. Growing 3’ to 4’ feet high, it produces many erect branches from the base of the plant, eventually making a dense, rounded shrub.
More commonly grown hydrangeas with large globular flower heads have flower clusters made up of completely sterile flowers.
Depending on variety and soil conditions, these are either red or blue, sometimes white. Hydrangea macrophylla coerulea, however, has a flat flower cluster. 5 to 6 inches in diameter, but with both sterile and fertile flowers in the same cluster.
The large sterile flowers are outside the cluster (see above); small fertile flowers that form into seeds are in the center.
Soil Acidity Affects Flower Color
The color of the flowers frequently varies because of the soil acidity. The same is true of many of the other Hydrangea macrophylla varieties.
If grown in alkaline soil, they may be pink, and if in acid soil, they are usually blue.
The same is true of coerulea, with the difference that the small fertile flowers are a brilliant blue (when the plant grows in acid soil), and the larger ray flowers are often a lighter blue, possibly with white.
Experimental work has shown that the blue color is caused by the amount of available aluminum in the soil, the reason some growers merely say to “add alum” to ensure blue flowers.
Hundreds of garden varieties of Hydrangea macrophylla (formerly H. hortensiu or opuloides) exist.
They have been grown in the Orient for centuries and many in Europe and Australia, where they are also popular as garden or potted plants.
The variety coerulea is not one of the most conspicuous, but for bright blue flower clusters, it is one of the truly interesting Japanese natives.
44659 by Donald Wyman