Hydrangea Varieties

Arborescens
Hydrangea Arborescens

This variety is native to the United States. It is very hardy and blooms on new wood. It is the original 'snowball' hydrangea with white sterile flowers. Arborescens will bloom early, mid-season, and late.

Aspera
Hydrangea Aspera

Aspera is recognized for its huge fuzzy leaves and stems. The different varieties are native to the Himalayas, China, and Taiwan. This family grows very large and the flower color does not usually change with acidity. All varieties in the aspera family have unusually large lacecap shaped flowers.

Involucrata
Hydrangea Involucrata

This small shrub has fuzzy leaves that are pale green in color. Varieties were found in the early 1900s in Japan. Unusual buds are shaped like globes opening to oval shaped lacecap flowers which bloom early, mid-season and late.

Lacecap
Hydrangea Macrophylla Normalis

Lacecap flower heads are made up of small fertile flowers in the center with a ring of larger sterile florets around the outside. The flower head has a comparatively flat, roughly disc-shaped appearance. Lacecap varieties are strong vigorous growers.

Mophead
Hydrangea Macrophylla

Mophead is a nickname used to describe the familiar 'snowball' bloom hydrangeas. The florets are sterile forming large colorful globular heads.

Paniculata
Hydrangea Paniculata

Paniculata varieties feature a panicle (cone shaped) flower head consisting of fertile and sterile florets blooming on new wood. Paniculatas are easy to grow and hardy to Zone 4a.

Petiolaris
Hydrangea Anomala

This is a climbing hydrangea featuring a white lacecap bloom. Several varieties were found in 1800s in the Himalayas, Japan and China.

Quercifolia
Hydrangea Quercifolia

This hardy variety is commonly called the "Oak Leaf" family of hydrangeas and is native to the United States. It is a large growing deciduous shrub except for the few hybrid dwarf varieties. Quercifolia has panicle (cone) shaped blooms that are made up of both fertile and sterile florets.

Serrata
Hydrangea Macrophylla Serrata

Originally found growing in the mountains of Asia, the serrata variety is usually a smaller, slender stemmed but lush growing, fully blooming hydrangea. The blooms are most often a mixture of colors that change as the plant ages. Serratas are hardy to Zone 6 and more drought resistant than other varieties once established

Pruning Hydrangeas

By
Russell Balge, Western Maryland Research and Education Center, University of Maryland, Cooperative Extension Service

It is often said that no pruning at all is better than wrong pruning. Proper pruning is especially important with hydrangeas, where the misguided actions of an inept pruner can spell disaster. If hydrangeas are properly fed and watered, they will bloom if never pruned at all, even if they become overgrown, a bit scraggly, and produce fewer, smaller blooms than if they were pruned.

With the exceptions of climbing hydrangeas such as Hydrangea anomala ssp. petiolaris and the shrubby H. arborescens and H. paniculata, which bloom on the current seasons growth, all other hydrangeas bloom on last year's growth and are essentially pruned in the same manner. All pruning, cosmetic or rejuvenative, should be done after the last frost in spring. Pruning in the late summer to early fall must be avoided at all costs, as it may encourage late growth that may not harden off for the winter.

Dead Heading

The first form of pruning, especially for the H. macrophylla, or lacecap hydrangea cultivars, is dead-heading, or removal of spent blooms. There is a prevailing philosophy that allowing the spent blooms to remain on the plant protects the buds of next year's flowers that are present along the existing stem during the winter. This appears somewhat dubious as the spent inflorescences deteriorate and blow away during the winter, and next year's flower buds do not seem to suffer. Come spring through early summer though, last year's flower heads must be removed lest they distract from the appearance of the current seasons bloom. Cut the spent blooms, along with the flowering stalk, back to the uppermost pair of new buds. Be careful not to damage any of the new green shoots.

Cleaning Up

"Cleaning Up" consists of removing any shoots that did not harden off by the onset of winter and which were damaged by early fall frosts, those damaged during the winter, and those precocious shoots damaged by late spring frosts. Cut these stems back to new, vigorous growth in late April to early May. Cut the entire shoot down to the ground if it shows no sign of rejuvenation. This severe pruning often results in a proliferation of new shoots from the base of the plant. Remove some of these stems to allow sunlight and air currents to reach the center of the plant. While the new stems will not bloom during the current season, they should put on a healthy display next season.

Rejuvenative Pruning

While a young hydrangea needs little pruning beyond dead-heading, the cutting out of dead stems, the removal of brown leaves, and the occasional errant vigorous stem that spoils the appearance of the shrub, older hydrangeas may need a much more severe pruning. Once the hydrangeas have matured, remove about one-third of the oldest wood each season. This allows light to penetrate to the center of the shrub and encourages replacement limbs. The best time to do rejuvenative pruning is during a mild break in winter weather in January or February when the structure of the plant is quite visible and there is no chance of injury to new shoots.

If a hydrangea has become excessively overgrown for its site and gnarled, or has become damaged, cut all stems off at 1.5 ft from the ground. While this will completely eliminate all bloom for the current season, it will result in a proliferation of new shoots. Thin the new shoots out to a sensible amount by cutting them off right at the ground. By fall, the shrub will have a good framework of branches and flowering should resume the following season. The new stems may be a bit weak and will need a second season to become sturdy. Remember that this type of severe pruning is reserved for unrepentant otherwise unretrievable hydrangeas.

Pruning Other Species

Cut all branches of H. arborescens back to about 1 ft in late winter. There is no danger of frost damage, as the flower buds have not yet formed. Growth will be rapid once it starts. The many blooms may be so heavy that they require support.

Cut the wood of H. paniculata back to two buds at the base of each stem in late winter. New shoots, bearing large paniculate blooms will result. Sometimes whole branches may be removed to reduce the size of the shrub. The fewer the number of branches on the shrub, the larger the panicles.

H. anomola ssp. petiolaris, the most familiar of the climbing hydrangeas, requires little pruning at all. Once it is established it is self-supporting and quite independent. I have found that it takes up to five years before the plant begins to bloom freely. The only pruning necessary is that to confine the plant within its designated space. Mature plants of H. anomola spp. petiolaris can climb to 75 ft. Removing dead flower heads close to the main stems promotes future blooms.

The two evergreen climbing hydrangeas, H. seemanii and H. serratifolia, are restricted to zone 9 so they are not hardy in Maryland. Even though after a slow start, the growth of these plants increases in vigor, the plants need very little pruning. Prune only to confine them to their designated area. Cut them back a bit if they are growing on a wall, to encourage them to fully clothe the wall without projecting too far out from the wall.

Timely Horticulture Tips

The University of Georgia College of Agricultural & Environmental Sciences
Cooperative Extension Service

Growing Bigleaf Hydrangea

Gary L. Wade, Extension Horticulturist

Bigleaf hydrangea, Hydrangea macrophylla, also called French, Japanese or Snowball hydrangea, is both a florist plant and landscape plant in Georgia. Often purchased as a gift plant from florists, bigleaf hydrangea can be transplanted to the landscape for repeat blooms each year. Homeowners delight in changing the flower color from pink to blue or from blue to pink by adjusting the pH of their soil.

Location

Bigleaf hydrangea prefers morning sun, afternoon shade, and a moist, well-drained soil. Avoid planting it on hot, dry, exposed sites. Cold damage to the buds may occur in winter and late spring, so be prepared to provide some winter protection by covering the plant with an old sheet, blanket or cardboard container when temperatures drop below freezing. A cylinder of chicken wire placed around the plant and filled with leaves also provides excellent cold protection.

Bigleaf hydrangea can easily be grown in containers and is an excellent patio plant. Another advantage of growing the plant in a container is that it can be moved indoors on a cold night.

Planting

If possible, prepare the soil in a wide area. Apply 50 pounds of a composted organic matter per 10 square feet and incorporate it thoroughly into the top eight to 12 inches of soil with a tiller or shovel. Organic matter holds nutrients and water in the soil and helps prevent stress from wet/dry fluctuations in soil moisture.

Don't fertilize until the plant is established (4 to 8 weeks after transplanting). The majority of Georgia soils are acidic, so initial flower color will likely be blue.

Make certain the top of the root ball is level with the soil surface, and water thoroughly immediately after transplanting. Apply three to five inches of an organic mulch, like pinestraw, pine bark or fall leaves to the soil surface to conserve moisture and control weeds.

Fertilization and Watering

Bigleaf hydrangea responds to several light applications of fertilizer during the growing season. A general-purpose fertilizer, such as 8-8-8 or 10-10-10 applied at a rate of one pound (2 cups) per 100 square feet in March, May and July is suggested. It is not necessary to remove the mulch when fertilizing, but water soon after application to help dissolve the fertilizer and send it into the soil.

Bigleaf hydrangea is a water-demanding plant for the moderate water-use zones of the landscape. Water whenever the plant begins to wilt in the absence of rainfall. The avoidance of plant stress is particularly important during the spring months when the flower heads are forming.

Flower Color

Research has determined that the actual mechanism of color variation is due to the presence or absence of aluminum compounds in the flowers. If aluminum is present within the plant, the color is blue. If it is present in small quantities, the color is "in between," and if it is absent, the flowers are a pink.

The soil pH indirectly affects the color by affecting the availability of aluminum in the soil. When the soil is acid, aluminum is generally more available to the roots. When the soil is alkaline, the availability of aluminum is decreased and the flowers are more pink.

To gradually change flower color from pink to blue, broadcast 1/2 cup of wettable sulfur per 10 square feet and water it in. To make the flowers pink, broadcast one cup of dolomitic lime per 10 square feet and water it into the soil. It may take a year to see a noticeable change in flower color from this treatment.

Another, quicker way to achieve a change in flower color is through liquid soil drenches. To make the flowers blue, or perhaps more blue during the growing season, dissolve one tablespoon of alum (aluminum sulfate) in a gallon of water and drench the soil around the plant in March, April and May. To make the flowers pink, dissolve one tablespoon of hydrated lime in a gallon of water and drench the soil around the plant in March, April and May. Avoid getting the solution on the leaves because foliar damage may result.

Failure to Flower

Failure to flower is sometimes a problem with bigleaf hydrangea. This can be caused by winter injury to the flower buds, pruning in the late summer, growing the plant in too much shade, or applying excess nitrogen fertilizer.

Bigleaf hydrangea forms its flower buds in late summer for the following year, so pruning in late summer, fall and winter will remove potential flowers.

Pruning

Prune bigleaf hydrangea when the flower heads begin to fade. Prune out the flower heads and head back other shoots to encourage branching and fullness. Flower buds will begin forming in late summer for the following season, so avoid pruning after August 1.

Propagation

One of the easiest ways to propagate bigleaf hydrangea is by layering. This is done by digging a trench near the plant and bending a section of limb down into the trench. Use a knife to remove a small ring of outer bark about one inch wide all the way around the limb where it contacts the soil. Then, cover the limb with soil, leaving six to 12 inches of the tip growth uncovered. If layering is done during the summer, the new plant should be ready for transplanting the following winter.

Old established hydrangeas may also be divided in the early spring, by using a shovel to divide the clump. Several plants can be obtained from a well-established clump.

The University of Georgia and Ft. Valley State College, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability.

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