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Tag: Hydrangeas

Pruning Hydrangeas

Pink big leaf hydrangeas
Prune mophead bigleaf hydrangeas in summer just after blooming.

Timing and method are essential when it comes to pruning hydrangeas, and they differ depending on the species being pruned. If done improperly, you may prune off next year’s flower buds or cause your shrubs undue stress. On the other hand, making the right cuts at the right time will help keep them looking great and flowering to perfection.

Good Pruning Technique

The right techniques and tools are key to good pruning. Here are the basics.

The Best Pruning Tools

Sharp loppers, hand pruners, and hand saws
Choose sharp loppers, hand pruners, and hand saws for easy pruning.

For small branch cuts (up to 1 cm thickness), choose a quality set of sharp bypass pruners (avoid anvil pruners, which dull quickly). Bypass pruners are easy to sharpen and long-lasting, if you choose a high-performing brand (I like Felcos). For larger branches (up to 4.5 cm thickness), choose sharp bypass loppers. More powerful pruning tools may be needed for large panicle hydrangeas that become tree-like. For larger cuts, opt for a small, sharp pull-stroke pruning saw to cut through tough branches in no time!

How to Prune

Making the right cuts to branches will facilitate good plant health. Cuts to small branches should be made 2/3 cm from the adjacent stem. Make them at 45-degree angles. Larger branches should be cut flush to the trunk collar. The collar is the ripple of bark that will slowly and protectively grow over the cut. Cuts made above the collar will not heal properly, leaving plants vulnerable to pests and disease.

How Much to Prune

A stem with a 45-degree-angle cut
Make 45-degree-angle cuts 2/3 cm from the adjacent stem. Don’t damage lower buds!

Prune to the desired height, but beware of over-pruning. Refrain from pruning over 1/3 of the top growth, especially in smaller shrubs with well-branched woody top growth. Some species, such as smooth hydrangea (Hydrangea arborescens), are clump-forming with stems that can be harshly pruned back if the clumps are well established and have become overgrown. Others, like panicle hydrangea (Hydrangea paniculata), can become tree-like and require more selective pruning.

When to Prune

Hydrangea pruning time is species-specific. Follow the following guide for the top four garden hydrangeas.

Pruning Bigleaf Hydrangeas

Purple hydrangeas
Mopheads have a rounder more formal growth habit.

Latin Name: Hydrangea macrophylla
Best Time to Prune: These hydrangeas bloom on second-year wood, so the best time to prune is in midsummer, just after they bloom. If you prune in later summer or fall, you will cut off next year’s flower heads. Deadwood is common, especially in spring. Dead or dying stems can be removed at any time of year. Old blooms can also be removed at any time, as long as you just remove the flowers and not the buds that have developed below them.

Blue big leaf hydrangeas
Pruning bigleaf hydrangea in fall will remove next year’s flower buds causing irregular flowering the following year.

How to Prune: These hydrangeas can grow too large or develop ungainly stems that have grown too high — shape plants by cutting wayward or old stems to the ground. Stems can also be trimmed to the desired height, depending on the density of the overall shrub. Refrain from shearing bigleaf hydrangeas if you want to maintain a more naturalistic, appealing appearance.
Comments: Bigleaf hydrangeas can have either lacecap (Hydrangea macrophylla var. normalis) or mophead flower clusters. Lacecaps have a looser more naturalistic horizontal growth habit and should be pruned less formally. Mopheads tend to have a rounder habit better suited to uniform pruning. In northern zones above USDA Hardiness Zone 6, these shrubs may die to the ground, so they will never flower. Protecting the crowns with Fafard Premium Natural and Organic Compost and straw can help protect their flowering stems from the winter cold.

Lacecaps
Lacecaps have a more naturalistic habit and require selective pruning.

Pruning Oakleaf Hydrangeas

Standard oak leaf hydrangeas
Standard oakleaf hydrangeas are tall, broad shrubs.

Latin Name: Hydrangea quercifolia
Best Time to Prune: Oakleaf hydrangeas also bloom on second-year wood and should be pruned just after blooming in midsummer. Once shrubs have leafed out in spring, identify and remove any dead wood from the previous year.
How to Prune: Some compact oakleaf hydrangeas have rounder, tidier habits but most reach 8-feet in height and develop a broad, naturalistic habit. Remove overgrown or crossing branches. If they overgrow an area, shrubs can be hard-pruned back by half in midsummer. Just be sure to leave plenty of green leafy branches for strong growth, and keep newly pruned shrubs irrigated through dry summer days to encourage new growth and bud set.
Comments: The pretty flower panicles of oakleaf hydrangea dry nicely and look good in winter gardens. Remove the old blooms in late winter to keep shrubs looking fresh in spring.

Dry flowerhead of oak leaf hydrangea
Keep the dry flowerheads of oakleaf hydrangea on plants for winter interest.

Pruning Panicle Hydrangeas

Panicle hydrangeas
Panicle hydrangeas are hardy and best pruned in late winter or early spring.

Latin Name: Hydrangea paniculata
Best Time to Prune: These tall, hardy hydrangeas bloom on new wood, so the best time to prune is in late winter or early spring. Remove ungainly or crossing branches and dead wood at this time. Refrain from summer pruning, and avoid removing more than 1/3 of the top growth at pruning time.
How to Prune: Panicle hydrangeas are variable shrubs that tend to be tall (8-15 feet) and bushy or tree-like, but some cultivars are compact for small-space gardens. Selectively prune bushy varieties, cutting tall branches to the trunk or base of the plant. Cut the large branches of tree-like varieties to the trunk, making sure cuts are flush to the collar.
Comments: These shrubs revive quickly from pruning. Tree-form plants may develop suckers from the base of the trunk. Keep these pruned off to maintain a single trunk. The dry blooms of panicle hydrangea also look good through winter but should be removed in spring.

Pruning Smooth Hydrangea

Incrediball™ Hydrangeas
Large-headed smooth hydrangeas, like Incrediball™, should be pruned to 1/3 height in late winter. (Image thanks to Proven Winners)

Latin Name: Hydrangea arborescens
Best Time to Prune: These easy-to-grow hydrangeas also bloom on new wood and are best pruned in late winter or early spring. They respond well to harsh pruning and can even be pruned to the ground if they outgrow a space. By late spring, they will have grown back with vigor. Refrain from summer pruning.
How to Prune: Pruned these bushy shrubs uniformly to keep their habit rounded. Large-headed varieties, like Incrediball™, are top-heavy and appreciate regular pruning to 1/3 height to keep stems shorter and sturdier. Refrain from pruning large-headed varieties to the ground.
Comments: The bushy dry flower heads look great in winter but should be removed by spring. These hydrangea root very easily from cuttings. Take any pruned branches, dip them in rooting hormone, stick them in the ground, and keep them evenly moist. They will root in no time!

The Best Landscape Hydrangeas

Best Landscape Hydrangeas Featured Image
Hydrangeas, circa 1970, were a bit of a bore, represented by a few stodgy standbys such as the Victorian, mophead-flowered PeeGee hydrangea (Hydrangea paniculata ‘Grandiflora’). Today, however, they’re the epitome of horticultural cool, with numerous new and exciting varieties to choose from.

Panicle Hydrangea Hybrids

Hydrangea paniculata 'Tardiva'
Hydrangea paniculata ‘Tardiva’

Witness, for example, what’s happening in the world of panicle hydrangea (Hydrangea paniculata). Where once there was only ‘Grandiflora’, there now are dozens of seductive cultivars of this East Asian native, in a variety of shapes and colors. Many bear lacy, white steeples in the manner of ‘Tardiva’, an old (and – until recently—neglected) variety that is still unsurpassed for its showy blooms that peak in August and September, weeks later than most other paniculatas. Comprising both large, sterile florets and small, fertile florets, the blossoms possess an airy elegance that eludes ‘Grandiflora’ and other sterile-flowered, mophead forms. Numerous other excellent ‘Tardiva’ types – such as ‘Kyushu’ and ‘Chantilly Lace’ – have recently entered the scene. Most flower in midsummer.
Fafard Garden Manure Blend pack

Some recent cultivars come in hues and sizes that are new to the paniculata tribe. The lacy spires of ‘Pink Diamond’ and the early-summer-blooming ‘Quick Fire’ gradually evolve from white to dark pink, passing through a beguiling bicolored phase along the way. In contrast, ‘Limelight’ deepens its snowball blooms to an astonishing chartreuse-green that glows most brightly in partial shade. The dwarf cultivar ‘Little Lime’ does similar things on a smaller scale (4 to 5 feet tall rather than the typical 8 to 12). It exemplifies another welcome paniculata trend: compact cultivars that fit nicely in smaller gardens. White-flowered examples include ‘Little Lamb’ and ‘Bobo’.
Even the stodgy old PeeGee hydrangea has undergone a makeover, with the introduction of several cultivars (including ‘Unique and ‘Webb’s’) that outdo ‘Grandiflora’ in the size and showiness of their snowball inflorescences.
Most paniculata cultivars respond well to severe pruning in early spring, which restricts their height, increases their inflorescence size, and slightly delays their bloom. In whatever form, they’re among the hardiest and most adaptable ornamental shrubs, thriving in full to partial sun from USDA hardiness zones 3 to 8.

Big Leaf Hydrangea Hybrids

Hydrangea macrophylla 'Harlequin'
Hydrangea macrophylla ‘Harlequin’ only performs well in USDA zones 6b to 9. (photo by Jessie Keith)

Cold-hardiness is much more of an issue for undoubtedly the most popular hydrangea species. Prized in USDA zones 6b to 9 for its reliable summer display of showy blue, pink, or white blossoms, bigleaf hydrangea (Hydrangea macrophylla) has long been the despair of gardeners in zones 5 to 6a. There, it typically dies to the ground in winter, resulting in a disappointing summer display of lush foliage and few to no blooms. Breeders are hard at work, however, on a new generation of “re-blooming” cultivars that flower on the current year’s growth. Several have made it to market, including the much-hyped blue-flowered mophead ‘Endless Summer’.

To date, none of these ballyhooed newcomers are consistent performers in zones 4 and 5, alas. But for gardeners in milder zones, these and other recent introductions make for a larger selection of Hydrangea macrophylla cultivars than ever before.

Several other highly ornamental East Asian hydrangeas (such as Hydrangea serrata, H. aspera, and H. heteromalla) are increasingly available from American nurseries. All are well worth trying, where hardy.

Smooth Hydrangea Hybrids

Ivory hydrangeas
Most new sooth hydrangeas have attractive globes of ivory, sterile florets.

Two eastern North American species have also seen a significant fashion upgrade in the past few decades. Fifty years ago, smooth hydrangea (Hydrangea arborescens) meant one thing: ‘Grandiflora’, commonly known as Hills of Snow. A classic pass-along plant, this suckering, 4-foot shrub formed many a backyard thicket, topped in summer by mildly ornamental, loosely structured, 6-inch globes of dull-white sterile florets.

Today, ‘Grandiflora’ has numerous successors, most operating on a grander (and floppier) scale. Their queen mother is the ubiquitous ‘Annabelle’, whose foot-wide midsummer domes are notorious for toppling. Her several imitators, such as ‘Incrediball’, also topple, as does the recently introduced pink-flowered snowball, ‘Invincibelle Spirit’.

Gardeners looking for a sturdier (and more charming) arborescens variety can opt for the ravishing ‘Mary Nell’, which bears showy, stylish, snow-white lacecaps on stout 4-foot stems. Another wonderful option is Hydrangea arborescens ssp. radiata, whose leaves are often lined underneath with a luminous silver-white felting that flashes in the breeze.

Oakleaf Hydrangea Hybrids

Hydrangea quercifolia 'Alice'
Hydrangea quercifolia ‘Alice’ (photo by Jessie Keith)

Oakleaf hydrangea (Hydrangea quercifolia) is yet another eastern U.S. native that offers many more delicious possibilities than ever before, including several pink-flowered and double-flowered varieties. The best (such as ‘Snow Queen’) produce showy spires on strong flop-resistant stems furnished with bold, deeply lobed leaves that turn burgundy-red in fall.

Full-size selections grow to 7 or more feet, but gardeners with more limited space can now choose from a bevy of excellent compact-growing cultivars including ‘Munchkin’, ‘PeeWee’, and Sikes Dwarf’. Of particular note is ‘Ruby Slippers’, a compact variety whose flowers age from the usual white to a much less typical deep pink.

Hydrangeas grow well in a variety of partial shade and sun locations, so long as they have fertile garden soil that drains well. Amending yearly with organic amendments, such as Fafard Garden Mature Blend, and top dressing with leaf mulch will help support plants and encourage best growth.

Hydrangea quercifolia 'Sikes' Dwarf'
Hydrangea quercifolia ‘Sikes’ Dwarf’