NEIGHBORHOOD GARDEN FOR FEBRUARY 16, 2008 *************************************************************  




·       “Should I plant my HYDRANGEA in full sun, part sun, or shade?”                                                            It depends.

·       “Will my HYDRANGEA bloom in the spring, in the summer, or the           late summer?”                                        It depends.

·       “When do I prune my HYDRANGEA?”          It depends.


I say “It depends” because there are thousands of varieties of Hydrangea and where you plant your Hydrangea, how you grow it, how you fertilize, when it blooms, what color the bloom will be, and when you prune it depends on the specie and variety you are growing. . In his new book on Hydrangea, Dr. Michael S. Dirr, professor of horticulture at the University of Georgia and recognized international expert on trees and shrubs, has chapters on each of the 9 major species of Hydrangea. In Chapter 11 he mentions many more minor species that are found around the world. (See Resources at end.)

As the fly cover of his book says, “The sheer number of Hydrangea species, hybrids, and cultivars can prove overwhelming even for the most advanced gardeners.  How to choose from the hundreds of mopheads, lacecaps, climbers, and oakleafs, to names just a few?”

          Gladys and I write most articles from our experience with the subject. This one is different in that both Gladys and I have very little personal experience with growing Hydrangeas. I started my reading as I had a hard time successfully growing a Hydrangea macrophyla ‘Nikko Blue’. I wanted that blue flower but could not even get it to flower let alone turn blue. I asked around and a few people gave me suggestions why. Then I tried to find someone to write this article and came to a dead end so I began to research why they would grow but not flower.

          Today I will share with you what I have learned from my reading. One expert wrote “Hydrangeas do not usually bloom because: (1) Too much pruning, (2) improper pruning time, (3) weather--too cold or the transition to and from winter/summer too drastic, (4) too much shade, or (5) too much nitrogen fertilizer.” (Hydrangeas Plus newsletter for November/December 2007)

          I think number 3, the weather, is probably the biggest reason most Hydrangea macrophyla, especially in Southeast and South Central Nebraska, do not bloom. As I look back, I know this was why my Hydrangea macrophyla did not bloom.

          I found an article in the “Horticulture and Home Pest News” from Iowa State that had the best description of why certain Hydrangeas don’t bloom and also about other Hydrangeas that are good for the Upper Midwest and zone 5. The following is from that article “Hardy Hydrangeas” by Cindy Haynes, Department of Horticulture, Iowa State University, Horticulture and Home Pest News for June 22, 2001.

          “The Big Leaf Hydrangea (Hydrangea macrophyla) is the colorful shrub we see in florist shops and super markets and desire in our landscape. One variety is referred to as a “snowball plant” because of its big round flower. However, this variety of Hydrangea is not hardy in zone 5. It will grow but the Big Leaf Hydrangeas bloom on previous season’s growth (old wood) and since the stems often die back to the ground in the winter, they seldom bloom.  Even placement in a protected site with fertile, moist, well-drained soil, will not guarantee blooms every year.”

          “But wait!!! Don’t give up on Hydrangeas yet. There are a wonderful group of summer blooming shrubs with several species that are hardy in our zone 5. These include the Smooth Hydrangea (Hydrangea aborescens) that flowers freely from June to September. The flowers are rounded and change from an apple green to cream white during the summer. ‘Annabelle’ is one of the most popular cultivars and noted for its large (almost 1 foot diameter) flower heads.”

          According to Dr. Michael A. Dirr in his book on Hydrangeas, “The Smooth Hydrangea (Hydrangea arborescens) will reliably produce flowers in gardens from Alberta, Canada, to North Florida. The most common variety is ‘Annabelle’. At a certain stage the big flowers are green in color and prized by those who prepare and arrange dry flowers as well as fresh. Most seeds of ‘Annabelle’ produce sterile-flowered, globose (globe shaped) to round-shaped, white, mophead offspring.” In spite of this problem with the seeds, Dr. Dirr has a goal to breed a pink type of ‘Annabelle’.

          A friend, Bob Henrickson who lives here in Lincoln and works a great deal with trees and shrubs for the Nebraska Statewide, has shared the following, “The Smooth Hydrangea ‘Annabelle’ does not tolerate drought very well, and consistent moisture and rich, organic soils should be encouraged for optimum bloom.”

          Many garden centers and especially box stores, hardware stores and drug stores sell “Hydrangea macrophylla” as hardy in zone 5. It is but beware as it probably will not bloom every year. One exception is the new variety called “Endless Summer” that was developed by Bailey Nursery in Minnesota and fully released in 2004. This variety blooms on both old wood (last season’s growth) and new wood (this year’s new growth) and is hardy to zone 4. It is becoming a very popular shrub and new cultivars are coming out each year, including ‘Blushing Bride’, a pink variety of ‘Endless Summer’. You might want to try one.

          In Hydrangeas Part #2 I will deal with some more varieties of Hydrangea that will do well in our area, and then in Part #3 will deal with fertilization and pruning.


·        “Hydrangeas for the American Gardens” by Michael A. Dirr, (Timber Press: Portland) 2004

·        “Hardy Hydrangeas” by Cindy Haynes, Department of Horticulture, Iowa           State University, Horticulture and Home Pest News for June 22, 2001.

· newsletter (Hydrangeas Plus: A division of VanHoose Enterprises, LLC, and P.O Box 389, Aurora, OR 97002)

· (Wilkerson Mill Garden, Palmetto, GA 30268)

·        “Pruning Hydrangeas”, Fine Gardening Magazine, The Taunton Press: Newtown, CT 06470-5506, May-June 2007, pages 51-53.

  • E-mail from Bob Henrickson, Assistant Director of Horticulture Programs for the Nebraska Statewide Arboretum

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