Native to Japan and possibly Korea, Hydrangea macrophylla has invaded the Azores and Madeira Islands. This variety has also been naturalized in China, America and also New Zealand. It’s a deciduous shrub which grows to 2 m (7ft) high and 2.5 m (8 ft) wide with large heads of pink or blue flowers in fall and summer.
The term macrophylla itself can be interpreted as large or long leaves. Leaves on the opposite side can grow up to 15 cm (6 inches). When viewed from its shape, this shrub is quite simple, acuminate, membranous and also orbicular to the elliptic. Just like other varieties Hydrangea macrophylla also needs intensive care so that the flower heads can bloom with massive sizes.
If you have grown Hydrangea macrophylla throughout your garden, to avoid this shrubs to not propagate uncontrollably, you should take a bunch of care that we’ll explain below!
Growing Hydrangea macrophylla
Several varieties of Hydrangea macrophylla will grow and flower on old wood. During winter, this plant must carry its flower buds. Either early or late freezing will damage the flower buds thus preventing them from blooming larger.
In Zone 5, this plant may only successfully bloom 3 out of 5 years, but the plant itself is vigorous there. Fortunately, gardeners in colder zones have recently introduced the fact that these plants do well, because they flower on newly grown stems that are about a year old.
Test the soils before planting Hydrangea macrophylla
Before you go on planting Hydrangea macrophylla, it’s better for you to test your soil to know the soil’s pH. We recommend you to visit your Local Cooperative Extension Service to find out anything about soil testing in your area. They’ll usually offer soil pH meters to allow you to test soil and provide accurate results.
In this case, pH largely determines the availability of aluminum in the soil as an element that is more widely available in acid soils. For Hydrangea macrophylla, the color of the flower is determined by the pH in the soil. At higher pH, the flowers will be pink and at low pH (acid soil) the flowers will be blue.
Meanwhile, a pH below 0.5 will produce a deep, bright blue color. When the pH rises, the flowers will change from blue to lavender to light purple to bright pink at pH 7.0 (neutral). If you want your Hydrangea macrophylla blooming with pink color in acid soil, you just simply add lime to increase the pH and use a balanced fertilizer.
In fact, the Aluminum sulfate will decrease pH if you want your Hydrangea macrophylla to have a blue color. As phosphorus binds to aluminum in the soil, sure using a fertilizer which is low in nutrients really helps to produce blue flowers.
Feed your Hydrangea in spring
Just like most Hydrangea varieties, macrophylla also needs enough fertilizer in order to produce large leaves and gorgeous flowers. Fertilizer really increases both the size and the number of the flowers on the plant.
Granular, stake or also liquid fertilizer can be a great option that you can use. The granular fertilizer must be worked into the soil around the plant at a rate of 2 pints or 2 pounds per 100 square feet of planting bed.
Alternatively, you can drill or punch 6” deep holes at the drip line of the plant. Afterwards, you can pour the fertilizer into the holes with a total of ¼ pound of fertilizer per foot of height. Instead you can spread the shrubs which are divided up and poured evenly between all of the holes.
In this case, those holes have to be filled with more than 1/3 of the fertilizer which must be top filled with the soil. It’s best for you if you fertilize your Hydrangea macrophylla once a year in early spring or in late fall after leaf drop before bud break.
If you use stake fertilizer, it’s such an easy way for you as you can only follow the instructions on the package. While, if you use liquid fertilizer, you should mix it with water and then apply it the same as you water the plant. This fertilization method with liquid fertilizer must be performed three or four times per year starting in late April and ending in mid July.
From any options of choosing the fertilizer, a balanced mix should be used 18-24-16 or 20-20-20 or 20-30-20. We think that organic fertilizers such as manure can be used with great results. However, the organic fertilizer must be worked into open soil at 100 sq. ft. of. bed area or at a rate of one bushel per ounce 6’ shrub.
Keep away your Hydrangea macrophylla from disease
Even though there’s no serious diseases that can affect your Hydrangea, sometimes the powdery mildew will potentially infect the foliage especially in humid areas with bad air circulation. To keep away your plant from disease, you can treat it with a proper fungicide if the problem is serious. Make sure to always rake up and destroy all fallen foliage in the autumn.
As a variety that grows with wide leaves and flowers, of course there is a possibility that this plant will grow large uncontrollably. Well, if you don’t want your Hydrangea macrophylla to grow big, then the thing you have to do is pruning.
Better for you to prune your Hydrangea macrophylla by the end of August. While, in spring you only need to prune out dead wood after the new growth has emerged.
More Info : How to Prune a Hydrangea Bush Into a Tree
For modhead varieties which bloom on both and new wood, cut back stems by about half if the plant is growing too tall by the end of August. You should also throw away some of the oldest stems at ground level to thin out the shrub as needed. In spring, you just need to prune out dead wood after the new growth has emerged.
However, deadheading the spent blooms of Hydrangea macrophylla regularly which bloom on both old and new wood will encourage repeat bloom on the current year’s growth. For transplanting, young Hydrangea macrophylla can be transplanted when dormant in early spring.