All about Hydrangeas (or, don’t it make my pink blooms blue?)

By Dr. Bill Barrick, Executive Director

The four seasonal hallmarks of the Gardens are camellias in winter; azaleas in spring; roses in summer; and chrysanthemums in fall.  But soon, hydrangeas may eclipse roses as we continue to add plantings of hydrangeas throughout the Gardens.

Each year we generally force over 1,000 six-inch pots of hydrangeas for our displays, incorporating three varieties – ‘Merritt’s Supreme,’ ‘Mathilda Gutges’ and ‘Libelle.’ These hydrangeas are treated as annuals, but within the last several years, we have been replanting ‘Merritt’s Supreme’ throughout the Gardens.

Hydrangeas are well adapted to our Southern gardens and as you drive around our city, you will see many well established plantings. While you will no doubt notice many are planted in full sun, my experience is that they prefer partial shade, particularly when in full bloom, as the large flower heads tend to wilt during the heat of the day.

Currently we have plantings of six different varieties of Hydrangea macrophylla – ‘Merritt’s Supreme,’ ‘Blaumeise,’ ‘Madame Emile Mouillere,’ ‘Tokyo Delight,’ ‘Nikko Blue’ and ‘Fuji Waterfall.’ With the exception of ‘Fuji Waterfall,’ all of these varieties are varying shades of blue, which brings up the most asked question about hydrangeas: flower color.

Soils in Mobile County for the most part are acidic, which makes aluminum more available and causes hydrangeas to turn or remain blue. ‘Merritt’s Supreme’ is a pink variety, but over time fades to blue unless the soil pH is altered. To make soils more alkaline, spreading lime around the plant will help, but may require multiple applications. Conversely, to make soils more acidic, aluminum sulfate applications may be made.

The other frequently asked question is how to keep cut flowers from wilting. The best advice is to cut the flowers early in the morning and submerge the stems up to the flower heads in a container for several hours. Removing the foliage may also help reduce water loss. Although I have mixed reports, recutting the stems and dipping the cut ends in powdered alum may prevent wilting. The best advice is to keep adequate water in the vase at all times to reduce the likelihood of wilting.