Gardening - Growing glorious Hydrangeas

I vividly recall beautiful blue Mophead hydrangeas gracing the side of my Grandmother’s home in Southern New Jersey. I was so fascinated by these large flowers. It just seemed to stand out among the other shrubs in the yard. I remember watching my Grandmother add what appeared to be a blue colored laundry detergent to water for the plant once a year. She explained that this gave the flowers their beautiful blue color. Once I moved to my own home in Saratoga County I had visions of growing that same striking blue ball-like flower in my yard. My family surprised me with two hot house grown Nikko Blue hydrangeas during the Mother’s Day flower rush several years ago. With great anticipation, I planted these two shrubs. However over the years, I have been very disappointed in the flowering of these shrub…recalling only one year of remarkable flowers! I absolutely love hydrangeas, but discovered I was not only choosing the wrong varieties to grow here, but also caring for them incorrectly.

Hydrangeas are very familiar sights in our region. They grace many old structures, camps and lakeside properties. But not all types are meant to grow in our area. There is confusion over which varieties grow best. There are basically four types of hydrangeas: the Big Leaf Hydrangea (macrophylla) or Mophead/Lacecap; the Oakleaf Hydrangea (quercifolia); the Panicle

Hydrangea (panculata); and the Smooth Hydrangea (arborescens). The blue variety I so loved at my Grandmothers home is the Nikko blue Big Leaf Hydrangea. They are most popular in retail outlets in our region around Easter and Mother’s Day. But beware, these big leafed florist hydrangea are cold tolerant only through zone 5b. We are zone 5a/4b. Although these shrubs will generally leaf out, consistent blooms outside the hothouse environment in the Saratoga Region is unpredictable. Spring in the North Country may bring early warm spells as we have seen over the past few weeks, then late spring frost. This can kill the developing bloom buds that grow on the stems of last season (old wood). Gardeners as far north as Canada have had success getting their Big Leaf varieties to bloom more fully with winter protection. They often use a frame work surrounded and covered by burlap. Before covering the top of the frame work, they place oak leaves inside the frame to insulate the hydrangea.

Another cause of failure to bloom in the Big Leaf Hydrangea is improper pruning. Blooms typically develop on old wood, so pruning early spring or late fall will eliminate the production of flower buds. These hydrangea don’t generally need annual pruning. They only require deadheading of the spent flowers and removal of dead stems. You can improve the plant performance with occasional snipping during bloom time at the soil level. Remove some of the oldest, woody canes at the soil line. If you want to keep the size in check you can also cut the longest canes at the soil line.

A fascinating feature of the Big Leaf Hydrangeas is the ability to change the shade of the bloom.

They can range from blue through the spectrum of pink with an adjustment in soil ph. (Thus, my Grandmother’s magical watering additive) In general, hydrangeas prefer slightly acid soil ph in the 5.5 to 6.5 range. To get pink flowers you must raise the ph to about 7.0. However, the soil amendments must be done the year prior to the desired color change. It is important to know your existing soil ph and type before trying any amendments. A trip to the master Gardener Lab at Cornell Cooperative in Ballston Spa with a soil sample is recommended. They can test your soil and make the necessary recommendations to increase or decrease your soil ph to the proper level. The Big Leaf hydrangeas generally do not tolerate full harsh sun. They prefer a part shade environment, preferably morning sun and afternoon shade.

If you really like the look, colors, and texture of the Mophead varieties but want a lower care plant choose the everblooming hydrangeas in the new Endless Summer line. These come in varying shades of pink, lavender and white. They are cold tolerant for our region, grow on both old and new stems, so no real pruning issues or problems with blooms being killed by late spring frost. My favorite in this line is the Blushing Bride. Your get profuse flower blooms and colors ranging from white, cream, to pink in the fall. I have had great success planting these in various environments in our region, in town, in slightly higher elevations, and lakeside.

The Oakleaf Hydrangea is native to the United States. This is a very popular variety that does well in our area as it is cold tolerant to zone 5a. These hydrangeas produce dramatic white blooms with a full four seasons of interest. They are a much lower maintenance shrub than many of the Big Leaf varieties, tolerating dryer conditions and far less fussy about pruning times. There blooms arrive later in the season, midsummer to first frost as they grow on the new wood of the season. They are more forgiving about pruning if pruning is not done at a specific time. If you want larger flowers on your plant, try cutting back the stems to soil level late winter/early spring.

I do however recommend leaving some of the canes at 18-24 inches above soil line as a framework for new growth. This reduces the branch flopping.

The Panicle or Pee Gee Hydrangea gets it nickname from its botanical name: paniculata Grandiflora. The flowers are cone shaped and transition from a white to pink as fall approaches.

They can grow 8-10 feet wide and tall. So give them plenty of room on your property. Unlike the Big Leaf hydrangeas, they tolerate more sun and require very little maintenance. You can generally prune them anytime, except of course when the buds are forming.

By far my favorite hydrangea to grow in our area is the Smooth Hydrangea (aborescens) or Annabelle. This is a remarkable white drumstick-like flower head that can grow up to 10 inches in diameter. They bloom every year even after severe pruning and extremely cold winters. A real versatile plant for our area it is cold tolerant to zone 4. Annabelle prefers morning sun and afternoon shade or dappled shade throughout the day. One challenge in growing Annabelle is supporting the heavy blooms. To avoid excessive flopping you can prune leaving the higher stems for support as directed with the Oak Leaf; put a short wire fence around the plant before it branches out (same concept as the framework used for peonies); or plant at least three Annabelle 3-4 feet apart for a hedge effect. They will support each other as they grow.

Hopefully the mysteries of growing glorious hydrangeas have been solved with this bit of information. If you choose to surprise Mom with this truly glorious plant, take a bit of time to read the plant label and choose the one that best meets your time and property needs.

Sue Ann DuBois is a Master Gardener and partner to the husband-wife team of Chips Landscaping. She designs, constructs, and maintains outdoor landscape, water gardens, and landscape watering systems. Chips Landscaping is an Aquascape® trained water garden contractor and member of the Aquascape® Water Garden Excellence Partnership. For more information visit: www.chipslandscaping.net