In Georgia, bigleaf hydrangeas, Hydrangea macrophylla, sometimes known as French, Japanese, or snowball hydrangeas, are grown both as landscape and florist plants. Bigleaf hydrangeas are frequently bought as gift plants from florists and can be moved to the landscape for yearly blooms. By modifying the soil pH, homeowners can alter the color of flowers from pink to blue or from blue to pink.
Two Main Groups
In the nursery industry, bigleaf hydrangeas come in more than 500 different cultivars. They can be split into two main categories: hortensias, which have huge flower clusters resembling snowballs, and lacecapes, which often have flowers with fairly flat tops, fertile blooms in the center, and showier sterile flowers on the periphery.
Location
Bigleaf hydrangea prefers moist, well-drained soil, morning light, and afternoon shade. Don’t plant it in exposed, hot, dry areas. Winter and late spring can cause cold damage to the buds, so be ready to offer some winter protection by wrapping the plant in an old sheet, blanket, or cardboard box when the temperature drops below freezing. Additional effective cold protection is offered by a cylinder of chicken wire surrounded by leaves.
Bigleaf hydrangea is a great patio plant that is simple to cultivate in containers. The ability to bring the plant indoors on a chilly night is another benefit of growing it in a container.
Planting
Prepare the soil over a large area if at all possible. Apply 50 pounds of decomposed organic material per 10 square feet and thoroughly work it with a tiller or shovel into the top 8 to 12 inches of soil. Organic matter keeps nutrients and water in the soil and protects plants from stress caused by changes in soil moisture from wet to dry.
Before the plant is established, don’t fertilize (4 to 8 weeks after transplanting). Since Georgia’s soils tend to be acidic, the first blossom color will probably be blue.
After transplanting, make sure the root ball’s top is flush with the soil’s surface and give it a good drink of water. To retain moisture and manage weeds, add 3 to 5 inches of an organic mulch to the soil’s surface, such as pine straw, pine bark, or fallen leaves.
Fertilization and Watering
Throughout the growing season, bigleaf hydrangea responds to many sparing fertilizer applications. It is advised to apply a general-purpose fertilizer, such as 8-8-8 or 10-10-10, at a rate of 1 pound (2 cups) per 100 square feet in the months of March, May, and July. When fertilizing, it is not required to remove the mulch; however, watering soon after application will help the fertilizer dissolve and go into the soil.
Bigleaf hydrangea is a water-hungry plant that does best in landscape zones with moderate water requirements. When the plant starts to wilt in the absence of rain, water it. Avoiding plant stress during the spring, when the blooms are developing, is especially crucial.
Flower Color
According to research, the presence or absence of aluminum compounds in the flowers is the real cause of color variation. The color is blue if aluminum is present in the plant. If it’s absent or only minimally present, the blooms are pink, and if it’s there, the color is “in between.”
Through influencing the amount of aluminum in the soil, soil pH indirectly influences flower color. Aluminum is typically more accessible to the roots in soil that is acidic (pH 5.5 or lower). Alkalinity (pH 7.0 or above) in the soil reduces aluminum availability and increases the pinkness of the blooms.
Distribute 1/2 cup of wettable sulfur per 10 square feet and water it in to gradually turn pink flowers blue. Spread one cup of dolomitic lime per 10 square feet and soak it into the soil to turn the flowers pink. The effects of this treatment on flower color could not be visible for a year.
Through liquid soil drenches, you can change the color of your flowers more quickly and easily. In March, April, and May, saturate the soil around the plant with 1 tablespoon of alum (aluminum sulfate) dissolved in 1 gallon of water to make the blossoms blue, or perhaps more blue. In March, April, and May, soak the soil surrounding the plant with a solution of 1 tablespoon of hydrated lime in 1 gallon of water to turn the blossoms pink. Avoid getting the mixture on the leaves to prevent foliar damage.
Failure to Flower
Bigleaf hydrangeas can have problems with flowering failure. This may be brought on by winter damage to the flower buds, overly-shady plant growth, an excess of nitrogen fertilizer, or untimely pruning. Pruning throughout the late summer, fall, and winter will eliminate prospective blossoms since bigleaf hydrangeas develop their flower buds in the late summer for the next year.
Pruning
When the bigleaf hydrangea’s blossoms start to fade, prune it. To promote branching and fullness, remove blossom heads and head back other shoots as appropriate. Avoid pruning after August 1 since flower buds for the following season will start to grow in late summer.
After a difficult winter, it may be necessary to prune plants to remove damaged foliage. The removal of winter-damaged leaf is healthier for the health of the plant and its aesthetically pleasing appearance, even though it will promote vegetative growth at the expense of flowering.
Propagation
Softwood cuttings collected in the early summer can be used to multiply bigleaf hydrangeas. Choose terminal cuttings from shoots that are not in bloom. A minimum of three leaves and a length of 3 to 5 inches should be present on each cutting. Make a little angle cut at the node (where the leaves are joined), then dip the cut end in a rooting hormone and plant it in a moist growing medium. To prevent wilting and dehydration, propagators frequently cut off the top half of each leaf. While the cuttings are rooting, keep them wet and in a shaded environment.
Layering is another method of bigleaf hydrangea propagation in the landscape. This is accomplished by excavating a trench close to the plant and bending a branch downward into the trench. At the point where the limb touches the ground, use a knife to carefully remove a narrow band of outer bark that is about an inch broad. After that, bury the limb in dirt, leaving 6 to 12 inches of the growth at the tip exposed. The new plant should be ready for transplantation the following winter if layering is done in the summer.
Early spring is a good time to separate clumps of mature, older hydrangeas with a shovel. A cluster that has been there for a while can produce many plants.
For More Information
On hydrangeas, there are several top-notch books accessible from publishers and online. Dr. Michael Dirr, a former professor at the University of Georgia, is the author of the book Hydrangeas for American Gardens. Both online and in bookstores, it is widely accessible. Additionally, the U.S. National Arboretum offers a fantastic online resource for choosing and growing hydrangeas. To learn more, visit www.usna.usda.gov/Gardens/faqs/hydrangeafaq2.html.
Associate in public service and coordinator of the state’s master gardening program; consumer ornaments
Have a concern?
To learn how our group of county agents can help you, get in touch with your nearby UGA Extension office.
Should I prune my bigleaf hydrangea?
Consider when your hydrangea blooms to see if it grows on old wood. These shrubs typically start blooming in the early summer and stop by midsummer, however isolated blooms may continue into the fall. Late summer or early fall, when the days grow shorter and the temperature drops, these shrubs begin to create the bloom buds for the following year. Pruning should be done just as the flowers start to fade to limit the chance of eliminating these buds. The sooner the shrub recovers after bloom, the more and bigger flowers it will produce the next season.
1. Old blossoms should be taken out to tidy up.
Gardeners can remove any wayward or straggly canes at the soil level and prune wasted blooms just below the flower head to keep their plants looking clean.
2. Eliminate the oldest canes to increase vigor.
A hydrangea may produce lesser blooms as it ages and becomes woody. The shrub will remain healthy and continue to produce big, many flowers if a few of the oldest canes along the soil line are routinely removed. The same technique, which involves removing the tallest canes, can prevent a shrub from becoming too tall.
Watch a video on pruning bigleaf hydrangeas
Almost everyone is mesmerized by bigleaf hydrangeas’ mophead blossoms (Hydrangea macrophylla and cvs., Zones 49). And it appears that queries regarding pruning these flowering bushes are common among gardeners. Because they are shrubs, it is frequently assumed that they require pruning. Some gardeners believe that pruning their hydrangea will encourage it to bloom. Both of these ideas are incorrect. Bigleaf hydrangeas don’t require any pruning, and if you prune them, you risk removing the bloom buds you were trying to receive by timing your cuts improperly.
The flower buds on bigleaf hydrangeas are often found on growth from the previous season, which is known as “old wood.” You will be removing the flower buds if you prune them before they bloom. Pruning too early doesn’t stop the entire display; rather, it stops a large chunk of it for many newer types that really generate buds on both old and new wood. However, if your hydrangea isn’t blooming, improper pruning is frequently to blame. Just after the bigleaf hydrangea has finished flowering is the ideal time to prune it. The shrub will have plenty of time before winter to establish new growth and harden off.
This video will provide you with the knowledge you need to timing your cuts properly and pinpoint where to make them on the shrub if you feel that pruning your bigleaf hydrangea is necessary. Only hand pruners and possibly a pair of loppers to reach deep into the hydrangea will be required of you. Wearing safety eyewear is also advised. While trying to gaze down into the shrub, it is quite easy to poke your eye on a stem, even if you don’t think they are cool. A poke in the eye is also never appropriate.
Can bigleaf hydrangeas be pruned in the spring?
Pruning is not typically thought of as one of the many gardening activities that may be done in the fall, despite the fact that there are several. It can be difficult to cultivate hydrangeas successfully in New Hampshire, and if you want your plants to blossom, there is frequently very little room for error in pruning.
Wait until Spring to prune hydrangeas
In New Hampshire, hydrangeas come in a variety of kinds, and each one has quite distinct growth patterns and pruning needs. Some plants only produce flowers on fresh growth, while others mostly produce flower buds on older wood. In any case, it is better to postpone all hydrangea pruning until spring. Hydrangeas, as with all other trees and shrubs, go dormant in the fall. Not much new growth is produced by them until the next spring. As new growth is more vulnerable to harsh cold at the location of wounds, plants that have been trimmed now run a higher risk of winter damage. Additionally, fall pruning may lessen the quantity of June blooms.
Considerations for pruning hydrangea species commonly grown in New Hampshire gardens
The gigantic blue mopheads or lacecaps known as bigleaf hydrangeas (Hydrangea macrophylla), which are familiar to most gardeners, form their flower heads at the tips of stems on old wood from the previous year. Although lower buds along the stem have the capacity to grow blooms as well, the hydrangea’s blossoming potential is decreased if those buds are died or damaged throughout the winter. Wait until new growth sprouts in the spring before pruning your bigleaf hydrangeas. Approximately 1/4 inch above the first group of live buds, prune the plant. A hint: the interior of living stems will be green, whereas the interior of dead stems will be brown. Cut completely dead stems flush with the base.
The three other hydrangea species that are frequently planted in Fresh Hampshire—oakleaf (H. quercifolia), panicle (H. paniculata), and smooth—all bloom on new growth. Before the emergence of the leaves in the late winter and early spring, remove wasted flowers and prune the plant to improve its general structure and habit.
In conclusion, there are a ton of other activities you can engage in to stay occupied in the garden during fall. Save the spring for hydrangea pruning.
When should hydrangeas be pruned in the year?
Depending on which group the plant belongs to, the timing and extent of pruning are determined:
Advice on Pruning for Group 1:
- As the days get shorter and the weather gets colder in the late summer and fall, buds for the following year’s blooms start to form.
- Typically, removing dead, diseased, or damaged branches is all that is required to preserve shape, size, and a healthy plant. Otherwise, gentle pruning ought to be practiced.
- In the summer, trimming should begin as soon as flowering ends, but no later than August 1. Pruning should not be done in the fall, winter, or spring because you risk removing fresh buds.
- Tip-pruning the branches in the spring as the leaves begin to appear can promote more numerous, smaller flower heads as opposed to fewer, larger flower heads.
Advice on Pruning for Group 2:
- On the growth of the current year, flower buds form.
- Early in the spring, as the leaves are starting to emerge, prune.
- Just above a node, prune branches back by half to a third.
- After that, prune any fragile or spindly branches.
- Minimal trimming encourages huge, strong bushes with many of tiny flower heads in H. arborescens. Hard pruning between 12 and 18 inches from the ground, or even all the way down, will result in fewer but larger flower heads that may flop if unsupported.
- For H. paniculata, remove the surrounding smaller wood while leaving the larger stems in order to establish a sturdy foundation.
Pruning may be connected to flower head size. Shoots will grow more vigorously and flower heads will be bigger and fewer with more rigorous trimming. Smaller but more numerous flower heads may result from less aggressive or tip pruning.
Consideration of hydrangeas’ mature size is the best piece of advise. Place them in a location where they won’t outgrow and won’t need a lot of pruning to keep them in check. Hydrangeas don’t need to be pruned precisely or often; as long as dead wood is removed, they will remain healthy and continue to develop and bloom.
Does my bigleaf hydrangea need to be deadheaded?
According to Meyers, the species of hydrangeas will determine the optimal time to prune them. When the initial set of flowers emerges from the previous year’s growth in the spring on bigleaf hydrangeas like Endless Summer, she advises, “deadheading to remove the faded blossoms before the next flush arises.” As long as the cut is made before July or August, when the plant starts to create buds for the blooms of the following year, you can make a deeper cut for a longer stem. She advises removing the faded blooms off smooth hydrangeas as soon as they turn green in order to guarantee a second flush of smaller flowers in the fall.