It Isn’t Summer Without Hydrangeas
Daniel J. Hinkley grew up in Michigan, a place with serious Zone 4 winters and a repetitive palette of two white-flowered varieties of hydrangeas.
In many front yards, you could see Hydrangea paniculata Grandiflora, known as the peegee hydrangea and often trained like a small tree, or a wider-than-high mound of Hydrangea arborescens Annabelle, with its large, rounded flower heads.
But a guy can dream, and Mr. Hinkley did — and traveled, too, becoming a modern-day plant explorer. Botanical travel, he said, has made him a better gardener, informed about plants’ use and care by seeing where and how they grow in nature.
“Hydrangeas are wild plants,” he said, “and part and parcel of ecosystems all over the place.”
In the wild, though, hydrangeas don’t look much like the ones he grew up with, or like the big-leaf pink- or blue-flowered mopheads, Hydrangea macrophylla, that gardeners in more forgiving climates than the Midwest think of as synonymous with the genus name, and crave. That’s because the ancestors of those cultivated varieties weren’t created for curb appeal, guided by human hands, but to attract and sustain pollinators, guided by evolution.
To do that, they have more of the inconspicuous but pollen- and nectar-rich fertile flowers and just enough of the showier, sterile ray florets to act as a billboard for insects. In some combination, these two make up the larger flower heads.
Mr. Hinkley, who opened a rare-plant nursery called Heronswood in Kingston, Wash., in 1987, found himself at his “seminal hydrangea moment” in 1997. He was looking “at miles and miles” of Hydrangea serrata on a steep, mossy South Korean mountainside. In “complete serendipity,” he said, he noticed one that was different.
Different in a way his plantsman’s eye — taking in aesthetics and subtler aspects of genetics — knew would appeal to gardeners, plus potentially contribute desirable breeding traits.
That oddball among serratas, with its double flowers of pink or blue depending on soil acidity, was introduced by Heronswood as Chiri-san Sue in 2000. Mr. Hinkley, who sold Heronswood 20 years ago, now has a partnership with the wholesale nursery Monrovia, which produces it, along with various other plants he has introduced, including other hydrangeas.
Many hydrangeas grow in Zone 8b at Heronswood — the property is now owned by the Port Gamble S’Klallam Tribe and operates as a public botanical garden — and at Windcliff, the garden of Mr. Hinkley and his husband, Robert Jones, who ran the nursery with him. A “climbing” hydrangea, Hydrangea anomala subspecies petiolaris, even does ground-cover duty alongside their shady driveway (and would be good tumbling over a low wall — or, of course, climbing).
“Hydrangeas really bring the garden back during the midsummer stutter,” Mr. Hinkley said. “They revive the garden all the way through fall.”
But he encourages gardeners to look for something different in them, as he has — extra hardiness, better foliage or maybe an unexpected flower form or color. From the daunting and ever-growing list of possibilities, he suggested some favorites as inspiration.
First, a Little More About Those Flowers
Most hydrangeas have a signature: clusters of tiny, fertile flowers encircled by ray florets.
The proportion of fertile to sterile, and the way they are grouped, varies widely. In many showy, long-popular garden varieties, you don’t see the fertile flowers at all.
In its natural form, Mr. Hinkley said, the typical hydrangea flower can be either a flattened lacecap or a cone-shaped panicle, “both possessing the sterile florets that act as notice to passing pollinators.”
In the case of better-known mophead hydrangeas — generally selected versions of macrophylla and paniculata “in forms rarely seen in nature,” Mr. Hinkley said — “the fertile flowers have been sacrificed for more, showier sterile ones.”
That’s “great for gardeners,” he added, “but not if you are a plant wanting to produce seed.” Or an insect.
How About a Smaller, Hardier Blue or Pink Hydrangea?
At a quick glance, you might mistake Hydrangea serrata, the mountain hydrangea, for a scaled-down macrophylla — the classic big-leaf hydrangea — but with lacecap-style flowers.
“For a small, partially shaded yard, you can’t get any better,” said Mr. Hinkley, who describes the four-foot serratas as “more demure.”
In Japan, he said, “they have cultlike status — there are literally hundreds of cultivars.”
Far fewer are offered here, but nurseries and gardeners are coming to appreciate their beauty and their extra hardiness.
“We find that the serratas are a full zone more cold-tolerant than macrophyllas,” said Adam Wheeler, the horticulture manager of Broken Arrow Nursery in Hamden, Conn., a longtime source for unusual plants. “They leaf out later, so they avoid late-frost damage that often zaps the big-leaf ones.”
At the nursery, on the edge of Zones 6a and 6b, the macrophyllas come through with their carried-over-the-winter flower buds mostly intact. In Mr. Wheeler’s home garden, a half-zone colder, he struggles. The serratas do fine.
Like the macrophyllas, serratas may flower blue or pink, depending on whether the soil is more acid (low pH) or alkaline (high pH).
If Velvety Purple Foliage Sounds Good …
The first purple-leaved hydrangea for American gardens was one that Mr. Hinkley brought back from China in 2006; it was introduced as Plum Passion by Monrovia a few years later. Now its progeny is in Monrovia’s lineup as Plum Passion Improved, with velvety plum foliage and mauve lacecaps.
Like many purple-leaved plants, the color fades in the summer heat, but there is another show. “The top side of the leaf goes butterscotch-gold and the bottom stays purple in autumn,” Mr. Hinkley said. “So when the leaves fall, it’s a carpet of two colors.”
Mr. Wheeler seconds the leaf appreciation. “I love hydrangea flowers, but try to find ones with great foliage to complement them,” he said.
Hydrangea aspera is another “awesome plant that people are missing the mark on,” he said, one that he would grow “even if it didn’t flower.”
Broken Arrow has six cultivars in its gardens, including Burgundy Bliss, an introduction from Michael A. Dirr, a professor emeritus at the University of Georgia. It has stood the test of four winters in Mr. Wheeler’s Zone 5b yard, despite reference books rating the species Zone 7.
There is more to this species than the ubiquitous Annabelle. If you find shades of pink appealing, Mr. Hinkley said, consider introductions from Thomas G. Ranney, a professor in the department of horticultural science at North Carolina State University. Dr. Ranney’s award-winning cultivars include Incrediball Blush and the deeper-colored Invincibelle Ruby, produced by Spring Meadow nursery.
The subspecies called radiata, with flashy, bright-white leaf undersides, is another favorite of Mr. Hinkley and Mr. Wheeler. It has more fertile flowers, so pollinators prefer it to overblown forms with fewer such flowers.
Another benefit: “If you had lights shining up under it at night, it would be a most dramatic thing,” Mr. Hinkley said.
Have Room for a Bigger Panicle Hydrangea?
Although the staggering number of recent introductions emphasize scaled-down size, Mr. Hinkley wants to put in a word for old-style Hydrangea paniculata, especially lacecap varieties like Unique and Tardiva. He confesses a lasting affection for the peegee, too.
“I’m not the standard customer, as far as the dwarf types go,” he said. “I prefer the grace of older varieties that were so tall their flowers rose above the garden.”
And as with Hydrangea arborescens, the pruning is simple, as they bloom on the current year’s wood — meaning you won’t be sacrificing flower buds by pruning in late winter or early spring. Cut them back as hard as you like.
Getting More From Mopheads
Mr. Hinkley and Mr. Wheeler both acknowledge the wow factor of macrophyllas, or mophead hydrangeas. But they also know that gardeners are disappointed when cold takes the flower buds — because your basic macrophylla blooms on old wood, which held the buds that formed the previous year and overwintered on the stems. And they know that many gardeners, wherever they live, are flummoxed by pruning them.
That explains the popularity of recent big-leaf varieties that bloom on old and new wood: They may repeat-bloom in a favorable climate where both the overwintered buds and the ones formed in the current year flower, or in colder spots, at least on those later buds, on the new wood. Endless Summer, from Bailey nurseries, was the first.
Or you could research the predicted hardiness in catalogs, but decide to take a gamble and push things a little, a process both plantsmen are familiar with.
“The jury is out on a lot of them, on how they will perform in gardens,” Mr. Wheeler said. “Because every time you turn your head, there are new ones. I try to tame my excitement to first see how they do before adding them to the catalog.”
A macrophylla that Broken Arrow always sells because it blooms reliably in Mr. Wheeler’s garden is Lady in Red, with blue lacecaps. Its name hints at its other attributes: red stems on new growth, and some red leaf veins, plus spectacular burgundy fall foliage. “You don’t think of hydrangeas, other than the native oakleaf, with that kind fall color,” he said.
The oakleaf, a Southeast native, is one hydrangea that doesn’t love Mr. Hinkley’s Zone 8b garden. It doesn’t flower well, and the dried-up leaves hang on stubbornly all winter. But he makes colder-climate gardeners jealous with others, including one of his early introductions.
Hydrangea angustipetala Golden Crane, or Mon Long Shou, blooms for him in April. It has a “beautiful perfume — an unusual attribute for hydrangeas,” he said, plus an unusual contrast between bright gold fertile florets and very large, jagged-edged sterile ones.
That particular hydrangea is hardy in Zone 6, but not necessarily happy, Mr. Wheeler can confirm. But he’ll keep trying.