NEIGHBORHOOD GARDEN FOR FEBRUARY 23

NEIGHBORHOOD GARDEN FOR FEBRUARY 23, 2008 *************************************************************

HYDRANGEAS PART #2

BY GEORGE EDGAR

· “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 cultivars/varieties of Hydrangea. Where you plant your Hydrangea, how you grow it, how you fertilize it, when it blooms, what color the bloom will be, and when you prune it depends on the specie and cultivar/variety you are growing. In regard to blooming, 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)

In part #1 I wrote about a couple of the species of Hydrangeas. I mentioned Smooth Hydrangea (Hydrangea aborescens), especially the cultivar ‘Annabelle’ that does very well in our area, and Hydrangea macrophyla that does not do very well in our area except for the new ‘Endless Summer’ cultivars. In Hydrangeas Part #2 I will deal with more species and cultivars of Hydrangea that will do well in our area. In Part #3 I will deal with fertilization and pruning.

The following is from an article “Hardy Hydrangeas” by Cindy Haynes, Department of Horticulture, Iowa State University, Horticulture and Home Pest News for June 22, 2001. “The Panicle Hydrangea (Hydrangea paniculata) blooms later than the Smooth Hydrangea, often not starting until July. But the 6 to 12 inch long, cone shaped, creamy white flowers are equally persistent. As the flowers age, they often become a mottle pink. This is the largest of the shrub-type hydrangeas often reaching 10 feet or more in height. There are many wonderful cultivars in this species with ‘Grandiflora’ being one of the most popular. This variety is hardy to zone 3.”

According to Dr. Michael A. Dirr, Professor of horticulture at the University of Georgia and recognized international expert on trees, and shrubs, Hydrangea paniculata is very easy to grow and will grow in acid and alkaline, moist and dry soils as long as drainage is “respectable”. The species prospers in heavier clay and clay loam soils and is the most drought tolerant of the major landscape species. Flowering is reasonable in partial shade, but in full sun produces the most floriferous specimens.

I have a friend, Bob Henrickson who lives here in Lincoln and works a great deal with trees and shrubs for the Nebraska Statewide Arboretum. He has shared the following. “The Paniculata cultivar ‘Tardiva’ seems to be performing great in Nebraska. This and Pee Gee seem to tolerate our heat (full sun) better than the arborescens types.”

Dr. Haynes says “One of the most interesting hydrangea species is the Oakleaf Hydrangea (Hydrangea quercifolia). Most Oakleaf Hydrangea have showy cone shaped, creamy white flowers in June and July. It prefers partial shade in fertile, moist, well-drained soil with protection from harsh winter winds. These cultivars vary in plant height from 2 feet for ‘PeeWee’ cultivar up to 13 feet on ‘Alice’.”

My horticultural friend Bob Henrickson says, “The Oakleaf hydrangea can get rather open and coarse with age but can be rejuvenated by pruning back by ½ after flowering. This will encourage new growth. This is also one of the only hydrangeas that gets a nice fall color. They seem to be heat tolerant as well and hold up rather well when planted in ¾ to full sun.”

Dr. Haynes also says in her article, “Not all hydrangeas are shrubs. One such example is the Climbing Hydrangea (Hydrangea anomala ssp. ‘Petiolaris’). Many notable horticulturists have praised Climbing Hydrangea as the best landscape vine. It clings easily to tree bark or other structures and is almost unlimited in its ability to climb often reaching over 50 feet in height. The white flowers appear in 6 to 10 inch diameter, flat-topped corymbs in early July and persist for several weeks.”

In regard to the Climbing Hydrangea Bob Henrickson here in Lincoln says, “This vine is one of the slowest vines to get established. Provided consistent moisture, with rich, organic, well-drained soil, they will grow more quickly. This is best sited protected from strong, southerly, summer winds, and in part shade to avoid the hot, afternoon, summer sun exposure.”

In regard to shade or sun, Dr. Dirr says we should adjust the siting of hydrangeas to their particular region of the country, topography, soils, and microclimates. “Common sense makes more sense than directions on paper, which at best should be viewed as a guide.” In other words, read the tag, talk to someone who has that cultivar/variety, and look at what the microclimate is in your garden.

Next time in Part #3 I will deal with fertilization and pruning of Hydrangeas.

RESOURCES:

· “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.

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

· Hydrangea.com (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