In the Garden:
Upper South
June, 2012
Regional Report

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Hydrangeas bring dramatic flowers to the summer garden.

Hooray for Hydrangeas

For much of the twentieth century, the hydrangeas grown in most gardens were limited to only a few different kinds. That has changed in recent years, as many new varieties have been introduced. What was once considered an old-fashioned Victorian shrub is now one of the most popular choices for the garden. All with good reason, as hydrangeas are easy to grow as long as the soil is well-drained, tolerate both full sun and partial shade, and provide showy flowers for many weeks from late spring well into summer. There are hydrangeas for any size garden, with choices ranging from ones that grow only 3 feet tall to others can reach 15 feet in height.

Most likely, at least one or more hydrangeas have found their way into your garden in the last couple of years. Have they fulfilled your expectations? Do you understand when and how to prune? Wondering which of the newer hydrangeas would be best in your garden? Let's take a look at the main type of hydrangeas.

Smooth Hydrangeas
The smooth hydrangea, H. arborescens, is native to woodlands in the United States from the East Coast as far west as Oklahoma and Kansas, withstanding temperatures to -40 degrees F. Garden varieties have much larger flower heads than those on plants found in the wild. Flowers appear on new growth of smooth hydrangeas.

The best known variety is 'Annabelle', with heads of white flowers up to 12 inches in diameter. The flower heads of 'Grandiflora' reach 6 to 8 inches in diameter. Both varieties grow 4 to 5 feet tall. If you're wanting color, try Invincibelle Spirit, with pink flowers. Besides 'Annabelle', one of my favorites is 'Hayes Starburst' with its double flowers on 3-foot plants.

Panicle Hydrangeas
The best known variety of the panicle hydrangea, H. paniculata, is 'Grandiflora', commonly known as PeeGee. Introduced from Japan in 1862, this was often grown as a specimen plant trained as a standard, making it appear as a small tree. Whether as a rounded shrub growing 8 to 10 feet tall or as a small tree, panicle hydrangeas grow and bloom on new wood and in a wide variety of climates. They are hardy to -40 degrees F and need more sun than other hydrangeas. The 6- to 8-inch-long clusters of white flowers are somewhat cone-shaped. As the flowers age, they turn a pinkish color. The flowers develop on new growth each year.

Of the newer varieties of panicle hydrangea, 'Limelight' is a favorite. The shorter-growing 'Little Lime' is a good choice for smaller gardens. The bi-colored flowers of Vanilla Strawberry and Pinky-Winky make them intriguing. As part of Chicago Botanic Gardens six-year evaluation program, the top performing panicle hydrangeas included 'Big Ben', Angel's Blush Ruby, 'Dharuma', 'Unique', 'Little Lamb', and the aforementioned 'Limelight'.

Oakleaf Hydrangeas
Native to the southeastern United States, the hydrangea, H. quercifolia, is one of the most handsome plants for the garden. Forming a full, rounded mound 4 to 8 feet tall and as wide, the oakleaf hydrangea has lobed leaves that turn burgundy in autumn and cinnamon-colored peeling bark on the stems. This gives additional appeal in the garden after the 4- to 12-inch-long, cone-shaped clusters of white flowers, opening in June, fade to a pinkish shade. Oakleaf hydrangeas are hardy to -20 degrees F. Flower buds are produced on the previous year's growth.

'Alice' is the tallest growing variety, sometimes reaching 10 to 12 feet tall and wide. 'Snowflake' has a double-flowered appearance, while 'Snow Queen' has particularly showy flowers and red fall leaf color. The flowers of 'Amethyst' turn a wine-red with age. Have a smaller garden? 'Pee Wee' and 'Sikes Dwarf' each grows 3 to 5 feet tall, but both still produce plenty of flowers. 'Little Honey' is coveted both for its diminutive size and the golden-to-chartreuse foliage.

Bigleaf Hydrangeas
The bigleaf hydrangea, H. macrophylla, is a plant of many forms. The flower heads may have a delicate lacecap form, with both sterile sepals and fertile, budlike true flowers, or may be large, rounded clusters, called mopheads. The most recognizable trait of this latter type is how, with some varieties, the flower color can be either pink or blue, depending upon the alkalinity of the soil. There are well over 500 varieties of bigleaf hydrangeas, most of which are hardy, at best, to -10 degrees F.

Because bigleaf hydrangeas usually bloom on the previous year's growth, many of us could not have them flower in our gardens. This all changed with the introduction of Endless Summer, a variety that was able to bloom on new growth. Subsequently, a number of similarly growing varieties have been introduced. I have yet to have much success with any of these, probably for a number of reasons, including my microclimate, which tends to be on the colder side of my zone, with late spring frosts and hot, humid summers. If you've experimented successfully with this type of hydrangea, congratulate yourself, but if yours haven't done well, focus on growing the other types. Tell me which ones have done well for you.

More Information About Hydrangeas
For greater detail about choosing and growing hydrangeas, there is a website and book that you should explore. Hydrangeas for American Gardens by Michael Dirr (Timber Press, $29.95, 2004) provides comprehensive information about this genus. The website, is a labor of love by Judith King, a member of the American Hydrangea Society. The site provides detailed information about the main types of hydrangeas, including how to plant, fertilize, prune, and change the color of hydrangeas, as well as how to dry them for bouquets. There is also a lengthy frequently-asked-questions section.

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