Hydrangea macrophylla ‘Harlequin’ only performs well in USDA zones 6b to 9. (photo by Jessie Keith)
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.
Witness, for example, what’s happening in the world of 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.
Hydrangea paniculata ‘Tardiva’
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.
Hydrangea quercifolia ‘Alice’ (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, 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.
Hydrangea quercifolia ‘Sikes’ Dwarf’
Two eastern North American species have also seen a significant fashion upgrade in the past few decades. Fifty years ago, 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 (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.