While pruning a neighbor’s neglected tree Hydrangea Lately I’ve found myself reflecting on the history of this genus in American gardening, its popularity rising and falling over the years. Grown across the country in many forms and used in countless ways, Hydrangea have found prominence in every gardening style. Often, hydrangeas are taken for granted and neglected, like this one I’m pruning. Yet even amid such disdain, this versatile ornamental plant has endured, attracting new generations of fans.
Basics of growing hydrangeas
(hi-dran-nam)
• The genus is mainly deciduous shrubs, small trees and climbers.
• Many cultivars are able to withstand USDA cold hardiness zone 4 (–30°F).
• Most people like to be protected from the harsh afternoon sun.
• Prefers moist, humus-rich soil but can adapt to many conditions.
• Generally resistant to pests and diseases.
More than 50 plant varieties hydrangea derived from five common species: H. Paniculata, H. macrophylla, H. quercifolia, H. arborescens, And H.anomala species petiole. Their height ranges from 18 inches to 30 feet, and their form can be climbing, dense shrub, or weeping tree.
Name hydrangea is from the Greek “hydor” (water) and “aggeion” (vessel), referring to their cup-shaped seed capsules. Hydrangeas are one of the easiest ornamental plants to grow, thriving in a variety of climates and conditions. They need humus-rich soil, enough moisture and protection from the midday sun. Add an annual pruning specifically for this plant, and you’ve met its needs. All are easily propagated by cuttings.
Cut H. panic for giant snowflakes
H. panic, Native to China and Japan, and thriving in USDA Hardiness Zone 3 (–40°F), it is a giant in its genus. A mature, well-preserved, well-placed specimen is a sight to behold. With its gracefully arching branches and luxurious, pyramidal clusters of snow-white flowers, then tinged with pink to dusty purple, and finally warm wheat-colored flowers, it deserves a standing ovation in my hall of high achievers—especially considering how few woody shrubs bloom during its showy season from July to September. With an upright habit—which becomes attractively vase-shaped and arching with age—it will reach 25 feet tall, with a spread of about 15 feet. It is typically grown as a large shrub or small tree, about 12 feet tall..
Because of the tree’s strong vitality, it should be pruned every year. For dense, bushy shrubs, “pinch” from the growing tips—snip off some of the leaf nodes—in early spring, shaping the plant while pruning old and dead wood. To get a small tree, prune lower and weaker branches from their base point, leaving three to five main branches close to the ground. From these branches, a dense, attractive canopy will grow. Thin annually in late fall or early spring to maintain shape and prune when desired height is reached.
If your H. bellflower overgrown, severe pruning is required in spring. For best results, fertilize first and wait a week or two. Then, take your pruning shears, tree saw, and hand pruning shears, and cut the tree back to the size and shape you want.
If you want larger flower clusters, reduce the number of buds developing. By focusing its energy on just a few buds, H. panic will produce flowers up to 16 inches long. These huge flowers will remind you why you chose this lovely ornamental plant for your garden.
Mophead hydrangea color is determined by soil pH
Probably the most precious member of the familyH. macrophylla has long been admired for its voluptuous flower clusters, which range in color from pink to red or blue to purple. It was one of the first plants to migrate from Europe, where it had been cultivated for centuries and was previously a popular plant in China and Japan.
H. macrophylla has a rounded habit, growing to about 5 feet tall with dark green, serrated leaves, up to 8 inches long, which in some varieties have cream-colored edges. The 6- to 10-inch flower clusters appear in midsummer and include both sterile (showy) and fertile (inconspicuous) flowers.
There are two distinct types of flowers H. macrophyllaThe best known type is the spherical-headed type with mostly sterile flowers. This is the original type Hydrangeaor mopheads, in our grandmother’s garden. The other is the disc-shaped lacecap, which has an inner fertile inflorescence surrounded by prominent sterile flowers (photo, facing page). Each type is gorgeous; trying to choose between them is futile—which is why I grow both types in my Brooklyn brownstone garden.
H. macrophylla is the litmus test of the garden. Blue to purple flowers indicate acidic soil. Add lime and they will be a pretty, soft red or a striking shade. If you want the pink and blue you want, add aluminum sulfate or an acidifying organic substance, such as oak leaf mold or peat moss. Or try throwing a penny under your bush; my neighbor credits her delicious purple flowers to this.
Although not very demanding and hardy to Zone 6 (–10°F), bigleaf hydrangeas still benefit from a little annual care. In the spring, dead wood should be cut back to live wood and older branches—the upper branches 3⁄4 inch diameter—should be eliminated. This will encourage new growth and improve flower quality.
General pruning to maintain size should be done soon after flowering, as lace flowers and mopheads flower on the previous year’s wood. In cold climates where heavy frosts are likely, some winter protection is recommended. Mulching leaves or spruce branches around the plant will reduce the chance of death and help ensure another season of blooms.
Oakleaf hydrangeas are the least demanding plants
The popularity of oakleaf hydrangeas (H. medicinal plants) has increased dramatically in recent years. While this species brightens the garden with its showy, erect clusters of white flowers in mid-July, it is best appreciated for its 6-foot-long, dark green foliage. Left unpruned, the spreading branches bear a profusion of lush oak leaves. When thinned selectively, it makes an exceptional specimen or potted plant. Thinning is best done in spring or immediately after flowering.
Oakleaf hydrangeas are the least demanding of this easy-care genus—tolerating both drier soil and more light exposure than the others—and will grow in deep shade. Native to the southeastern United States, oakleaf hydrangeas are hardy to Zone 5 (–20°F), where they can die back to the ground in winter. Because they flower on the previous year’s wood, this prevents any blooms, but the lush green foliage in spring and summer, russet foliage in fall, and beautiful, flaky winter bark are enough to make up for such a low-demanding plant.
Thin the old wood of the hydrangea smooth
Despite the objections of many fans, I consider the fluffy hydrangea (H. arborescens) is a poor relative of a prestigious family. After all, it requires more than 6 feet of garden space in all directions, producing an abundance of soft, heart-shaped leaves. It most closely resembles a mop, but the flowers are half the size and only come in white. Native to woodlands and stream banks from New York to Florida, and west to Missouri, it requires summer shade or supplemental moisture.
That’s right, it blooms from June until frost, when a few showy woody bushes add a little coolness to hot summer days. Yes, it is one of the hardiest and most reliable hydrangeas for flowering. It may freeze to the ground in Zone 3, but will recover in spring and bloom as flowers sprout from new growth. It is also the only hydrangea that is easily propagated by division; If it is too large for the allotted area, a portion can always be planted elsewhere. And, for good growth, thinning old wood in early spring will create a more attractive shape and larger flowers. Really not bad for a poor cousin.
Be patient with young climbing hydrangeas
H. anomala ssp. petiole-known previously as H. petiole—is the only vine of the genus hydrangea. Despite its slow start until the roots become established—usually two to three years after planting—the climbing ivy is a magnificent tree. It is remarkably vigorous and beautiful, reaching 60 feet tall thanks to its self-supporting aerial “roots,” which bear numerous heart-shaped leaves. The white flowers are flat, lacy clusters of both fertile and sterile flowers borne on stiff, upright stems in mid-June and July.
Patience is the best thing to provide during the first year or so of this East Asian native’s care, which is very difficult for Zone 4. After that, all you need are the manual pruning machine. Once established, climbing hydrangea will quickly fill its allotted space and continue to climb anything it can sink into. It works very well on walls and can climb trees, fences or any other structure without the help of ropes or nets. General pruning is best done immediately after the flowers fade, but touch-up work can be done at any time. With just a little care, long-lived hydrangeas will beautify your garden and delight generations of gardeners to come. I
With pruning shears in hand, horticulturist Keith Davitt tends to hydrangeas and enjoys gardening in Brooklyn, New York.
Source of hydrangeas
These mail-order nurseries offer all five species of hydrangeas, along with many other cultivars.
Carroll Gardens, 444 East Main St., Westminster, MD 21157; 800-638-6334.
Greener gardens, 1280 Goodpasture Island Rd., Eugene, OR 97401-1794; 541-686-8266.
hydrangeas plus, 6543 S. Zimmerman Road, Aurora, OR 97002; 503-651-2887.
Owen Farm, 2951 Curve-Nankipoo Rd., Ripley, TN 38063-6653; 901-635-1588.
Wilkerson Mill Gardens, 9595 Wilkerson Mill Rd., Palmetto, GA 30268; 770-463-2400.
