NEIGHBORHOOD GARDEN FOR APRIL 18, 2015

NEIGHBORHOOD GARDEN FOR APRIL 18, 2015 *************************************************************

HYDRANGEAS PART #1

BY GEORGE EDGAR

In February of 2008 I wrote a series of articles on Hydrangeas. I repeated these three articles in 2010 and am repeating now as many are still asking questions about Hydrangeas, do not know about the many wonderful varieties, and do not know whether to plant a particular variety in full sun, part sun, or shade. (Not all Hydrangeas like shade.) They also do not know when to prune the Hydrangea they have. As with most shrubs, if you prune at the wrong time of the year, you prune off the flower buds for next year.

Gladys and I write most of our articles from our own experience in our own backyard, from information we have learned in Master Gardener classes, and from reading about the topic. My reading usually starts with information that is backed up with University research.

I became interested and started my reading and research on Hydrangeas because 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. Gladys and I have very little personal experience with growing Hydrangeas, so I asked around and a few people gave me suggestions as to why. I wanted to find a local person who knew about Hydrangeas to write the original articles and came to a dead end. Therefore, I began to research why they would grow but not flower. Today I will share with you what I have learned from my reading and talking with friends who grow Hydrangeas.

One expert wrote “Hydrangeas do not usually bloom because: (1) Too much pruning, (2) improper pruning time, (3) weather---too cold and they winter kill or the transition to and from winter/summer is too drastic, (4) too much shade, or (5) too much nitrogen fertilizer.” (1)

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” ‘Nikko Blue’ did not bloom. This variety blooms on one year old wood and usually the new growth dies back over the winter so there is no one year old wood to produce flowers. The “Endless Summer” series that was developed by Bailey Nursery in Minnesota and fully released in 2004 is also a “Hydrangea macrophyla” (also called Big Leaf Hydrangea) but is a re-blooming variety so it blooms on one year old wood and on new wood.

Many homeowners want that blue color of the “Nikko’ and the ‘Endless Summer’ (Hydrangea macrophyla ‘Endless Summer’) and have had a hard time getting it to bloom the second or third year, or the blue color has turned to pink. As a result, they give up on trying to raise Hydrangeas. What they don’t realize is Hydrangea macrophyla ‘Nikko Blue’ and ‘Endless Summer’ and other blue Hydrangeas need sulfur to lower the pH to get the blue color or the bloom is pink.

Dr. Cindy Haynes, Department of Horticulture, Iowa State University, wrote “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 commonly 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 Hydrangea blooms 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.”(2)

She continues, “There are wonderful groups of summer blooming Hydrangeas 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.” Many call this the hardy “Snowball Hydrangea”. (2)

Many in Southeast and South Central Nebraska grow ‘Annabelle’ and enjoy the beautiful large flower. However, a friend, Bob Henrickson who lives here in Lincoln and works a great deal with trees and shrubs for the Nebraska Statewide Arboretum, 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.” (3)

Most people do not realize that a gardener, by putting in different varieties can have Hydrangea flowers blooming in the spring, in the summer, and in the fall. Dr. Michael S. Dirr, professor of Horticulture at the University of Georgia and recognized international expert on trees and shrubs, has a book on Hydrangeas with chapters on each of the 9 major species of Hydrangea, and in Chapter 11 he mentions many more minor species that are found around the world. 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 does one choose from the hundreds of mopheads, lacecaps, climbers, and oakleafs, to name just a few?” (4)

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.

REFERENCES:

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

2, “Hardy Hydrangeas” by Dr. Cindy Haynes, Department of Horticulture, Iowa State University, Horticulture and Home Pest News, June 22, 2001. (www.ipm.iastate.edu/ipm/hortnews)

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

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

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

6. Hydrangea.com (Wilkerson Mill Garden, Palmetto, GA 30268)