A Gardening Journal

The Best Season Ever: Climbing Hydrangea

Hydrangea anomala petiolaris 011616 overall 640

 

It's the rare deciduous vine that is even modestly attractive in the Winter. (Think of the rat's nest that is most honeysuckles and clematis from October through March.) Only a few vines—wisteria and trumpet vine tied for first place among them—might be grown, even if just in part, for their Winter display of bare limbs.

 

Climbing hydrangea is in a class of its own. With such an enormous potential for Winter display, you could choose to grow it so as to preclude its "normal" peak—the flowers—which, in one of the quirky ways you could handle climbing hydrangea, would only make the Winter display all the better.

 

I've begun to form a specimen of this Hydrangea anomala subsp. petiolaris by growing it up a pole. Actually, I'm growing it up four narrow boards of untreated pine that I tied around the true pole, a section of galvanized pipe. Climbing hydrangea climbs when its stems feel the presence of something sturdy enough to support growth, and that would also be grippable by the stems' profuse production of holdfast roots. Surfaces that are relatively soft (bark and most forms of wood) or rough or nubbly (bricks as well as stone that hasn't be polished smooth) are preferred. In the picture below, you can see some of the vertical pine boards behind a remarkably vigorous and colorful assemblage of climbing hydrangea stems.  

 

Hydrangea anomala petiolaris 011616 trunks 640

 

The colorful exfoliation of bark of the thick older stems is without equal in hardy vines, making climbing hydrangea a garden essential for that trait alone. Notice as well the striking chestnut warmth of the bark of the first-year stems. Sometimes these young stems follow the lead of their originating branch, and press against readily available support while anchoring themselves to it via holdfast roots. 

 

Hydrangea anomala petiolaris 011616 trunks closer 640

 

At other times, new young stems grow out into space, perpendicular to the climbing stems that grip any available support so tightly. In the picture below, this same climbing hydrangea is seen after the season's first heavy snow. The projecting stems can accumulate an enormous as well as attractive volume of snow. As is typical for hydrangeas, flower heads of climbing hydrangea provide two shows a year. The first is in Summer, when the flowers are fresh; the second is in Fall and Winter, after they have dried in place.

 

Hydrangea anomala subsp. petiolaris overall 012416 640

 

As seen from beneath, the profusion of flowerheads as well as new side stems couldn't be clearer. Climbing hydrangea is a vigorous plant that can cover almost any amount of supporting structure from rock ledge and walls to entire buildings. 

 

Hydrangea anomala subsp. petiolaris 012416 undersides showing branching closer 640

 

But mere size is perhaps the least impressive of its capabilities. Climbing hydrangea is so generous in its possibilities for year-round display that even a modest garden could have four or five specimens, each radically different from the others in size, shape, and propensity to flower. For a species with bizarrely few cultivars, climbing hydrange provides a bumper crop of variety nonetheless.

 

 

Here's how to grow this essential vining shrub:

 

Latin Name

Hydrangea anomala subsp. petiolaris

Common Name

Climbing hydrangea.

Family

Hydrangeaceae, the Hydrangea family.

What kind of plant is it?

Shrub that grows as a large-to-gigantic self-clinging vine.

Hardiness

Zones 4 - 8. 

Habit

Multistemmed and growing opportunistically, able to climb almost any structure when a rough or irregular surface is available, sprawling across the ground when not. Where stems can position themselves against a suitable climbing structure (wood and stone are best) with little side-to-side motion from breezes, anchoring holdfast roots are produced, and growth speeds up dramatically.

 

In all situations where free-range growth is permitted, the stems that climb or sprawl—let's call these the traveling stems—soon develop side stems two to four feet long. If the traveler has anchored itself well to its supporting structure, many of these new stems tend to grow right against the supporting structure, too. They form holdfast roots promptly, so as to anchor themselves securely and continue to grow as travelers. If the originating traveler isn't anchored (see the snow-covered picture detail, above), the new growth tends not even to attempt to anchor itself until contact is made with new supporting structure.

 

After the shrub itself is sufficiently old or established, or both, travelers also produce a second kind of side-stem. These stems project outward from the prevailing plane of growth of the travelers; they don't produce holdfasts. This projecting growth is known as (I blush to write) breastwood. Mature climbing hydrangeas can develop as massive a bulk of breastwood as that formed by ivy after it has entered its non-vining adult phase. If a given stem of breastwood is allowed to grow during the current season, it may form showy flower clusters at its tips the following season, just like stems of some other forms of hydrangea such as H. macrophylla and H. quercifolia. This two-year flowering cycle affects how, why, and when you prune climbing hydrangea; see the second "How to handle it" box, below.

 

See "Where to use it" and the second "How to handle it" boxes, below, for suggestions on siting and growing climbing hydrangea so that its overall vigor and tendency toward billowing breastwood can be controlled or celebrated as desired.

Rate of Growth

For the first year or two after planting, growth can be slow or, seemingly, non-existent. As the shrub establishes and—especially—stem tips can settle securely against suitable climbing structures and, so, can begin to adhere to them, growth becomes surprisingly quick: two to five feet a year. 

Size in ten years

Provided the growing conditions are good (see "Culture," below), climbing hydrangea's ultimate size seems to be limited only by the size of its host structures. With enough time, trees and walls sixty to eighty feet high could be scaled. In ten years, you could expect growth ten to twenty feet high and wide. Overall size as well as the bulk of the breastwood can both be controlled; see the second "How to handle it" box below. 

Texture

Full when in leaf; full-plus-fluffy when in flower. After the leaves have been shed in the Fall, a different show begins. The strong architecture of the older branches combines with their colorful and heavily exfoliating bark, plus the persistent lace-doily-like dried flower heads at their tips, to create a satisfying complexity of textures, colors, and shapes. Climbing hydrangea is a "full meal" year round. 

Grown for

its habit: Few families of shrubs are as diverse, colorful, long-blooming, and easy to please as hydrangeas. From Zone 3 through Zone 9, few gardens wouldn't benefit from the presence of several different forms. That there is also a vining member of this already bountiful family could, at first, look like too much of a good thing. Doesn't everyone already have various shrubby forms of hydrangea? And, yet, climbing hydrangea isn't merely an eccentric "sidebar" plant only of interest to tireless collectors; it is nearly the tail that wags the whole hydrangea dog. By comparison, all the other hydrangeas are mere shrubs —by definition, just groundhuggers—whereas Hydrangea anomala is, indeed, anomalous: Depending on how you handle it, climbing hydrangea could clothe a wall eighty feet square, race eighty feet up the trunk of a tree, scramble across bare rocks and ledge as a giant "ground" cover, lace itself up through lattice, be trained into tracery around doors and windows, or clothe vertical poles in thick cylinders of growth or in a traditional ball-on-a-stick profile known as a standard. And it does so with growth that is a visual feast year-round. And, yes, it flowers, too. If all hydrangeas were in a decathalon, climbing hydrangea would win every time.

 

Even more remarkable is the fact that climbing hydrangea also traditionally comes out first among vines. I can think of no other vine whose superiority is declared so strongly by cognoscenti who, by definition, have seen (and grown) everything. Michael Dirr: "The best vine!" Donald Wyman: "There is no better climbing vine." Right they are.

 

its flowers:  A scattering of showy sterile white flowers are at the outer edge of a disk (known as a corymb) of countless smaller, fertile, apetalous, greenish-white ones. The effect is at once understated—the opposite of the gigantic heads of countless sterile flowers, such as those of 'Invincibelle Spirit'—and, when a mature vine produces these heads by the hundreds, spectactular. The flowers are sweetly fragrant, too. The heads fade over the Summer, drying in place to produce a second show lasting much of the Winter.  

 

its flexibility: Because most stems of climbing hydrangea self-cling and, eventually, become thick and trunk-like, this vine can be left to grow ab libitum—or trained into almost any configuration. As with the "its habit:" rave above, climbing hydrangea can mature to a groundcover, a wall cover, a wall-hugging tracery, a standard, a column and, if you are particularly fussy and patient, screens such as a Belgian fence and a fan-limbed espalier. See both "How to handle it" boxes, as well as "Quirks and Special Cases."

 

its persistence: Like other woody vines, climbing hydrangea doesn't have a typical lifespan. As long as its preferred cultural conditions are at least minimally met, it seems to live indefinitely—and flower with abandon—without human intervention. But if a huge specimen ever needs a radical reconfiguration, that's possible, too. See the second "How to handle it" box.

 

its foolproof elegance: The low proportion of large (sterile) flowers to tiny (fertile) ones in each corymb combines with what, eventually, is an enormous number of corymbs on a huge mature specimen, to produce a show that is never cheap or obvious despite its visibility from blocks away. Climbing hydrangea is, thus, the "anti-rose" or "anti-wisteria:" Their floral displays are as voluptuous in detail (each individual flower or flower cluster) as they are (nearly) excessive in quantity. Thanks to its colorful exfoliating bark, climbing hydrangea also triumphs during the cold months in a way that no other woody vine can. And even if it is never pruned, its bulky and extensive growth still doesn't scream "I'm taking over the neighborhood" the way old specimens of trumpet vine, ivy, wisteria, climbing rose, and grape vine do.

 

its cold-season display: No other woody vine develops climbing hydrangea's colorful exfoliating bark. No other woody vine retains its flower heads in their dried form.

Flowering season

Flowering begins in June, and the show is spectactular. The intensity fades over the Summer as the flower clusters gradually dry in place, and also because their very persistence removes any element of surprise or newness. But after the leaves are shed in the Fall, the floral display you had forgotten to notice gets a second wind, and stays effective as long as the weather isn't so sustainedly rough that the clusters are broken apart.

Color combinations

The white flowers and green leaves go with everything—as do the tans and warm browns of the revealed bark in the leafless cooler months. That said, climbing hydrangea isn't coloristically "conversational." Yes, the showy sterile flowers are white—but they are only white, and a pure, sparkling white at that, without any contrasting details that could be referenced by nearby plants that are highlighting anything else. The apetalous sterile flowers provide a marvelous greenish-white frothy texture—but, again, no strongly contrasting color. The foliage is basic green, too. While no other color will clash with those of climbing hydrangea, the only colors that actively harmonize with it are other shades of green and white. And, so, the only plants that associate skillfully with climbing hydrangea are those whose display is either just green (albeit in any number of shades) or includes notes of pure white regardless of what other colors are also highlighted. See "Plant partners," below, for suggestions.

Plant partners

Because climbing hydrangea provides an active, detailed show year-round, the challenge with plant partners is to select and array them such that they, too, are active participants year-round. In general, devote more energy and space to partners that look great in the Winter; they'll also look at least passable in the Summer when the climbing hydrangea itself will carry the show anyway. Be sure that many of these year-round performers are evergreen, so they can provide a backdrop or underplanting for the hydrangea's unique display of exfoliating bark. Any size of evergreen leaves will coordinate well with the hydrangea's bare branches and delicate dried-in-place flower clusters. As always, darker shades of green are best, and if the evergreens can be trained into a clearly geometric shape, such as a hedge, all the better: That shape will be a spatial contrast to the trunks and stems of the hydrangea, which often adopt a writhing character. Avoid a preponderance of evergreens whose foliage is variegated, lest their patterning seem too busy near the already diverse array of colors of the hydrangea bark.

 

Only if there's still room is it worth it to consider partner plants with presence only during the warm months. Then the hydrangea's look is full, dense, and often heavy, so choose partners whose foliage is either delicate and fern-like (such as ferns themselves), broad and enormous (hostas or tropicals), or spear-like (ornamental grasses, iris, daylilies, or, in milder climates, phormium).

 

Because climbing hydrangea is so often growing in some degree of shade, partner plants will need to be shade-tolerant, too. Hostas might be the first choice, in that their leaves can be so large and so dynamically variegated. Both of these qualities are in pleasingly sharp contrast to the plain green, medium-sized hydrangea foliage. Shade-tolerant ornamental grasses that could grow at the base of climbing hydrangea include Hakonechloa macro and Phalaris arundinacea, both of which are usually planted as one of their spectacularly colorful named cultivars.

Where to use it in your garden

Climbing hydrangea is nothing if not versatile. If you are lucky enough to have any of the following features, one or more specimens of climbing hydrangea should be in your future. A large shade tree that tolerates underplanting; possibilities include tulip tree as well as almost any oak. A length of tumbled-down stone wall or a high or wide (or both) outcropping of ledge. A concrete-block garage that you need but can't stand to look at. A masonry wall that should have  another window or two but doesn't. A doorway or window through a masonry wall, around which you'd like to create a living frame. Two abutting areas that need only partially-dense screening to separate them. A (very) well-built pergola that you have some years to cover with a dense shade-casting canopy. Or—as in my garden—a spot in your garden that welcomes a vertical flourish with serious presence year-round.

 

The intricate array of muscular and, often, massive branches, the dried-in-place flower clusters, and the unique exfoliating bark each make climbing hydrangea a serious candidate to plant first and foremost for Winter display. Consider siting this shrub near a doorway or driveway, or prominently in view from a window, so that its details, large and small, can be savored no matter how nasty the weather is.

 

These usages can be in partial to fairly heavy shade or, if the soil doesn't become dry, in full sun.

Culture

Part sun to fairly heavy shade, in any soil with reasonable moisture retentiveness. Rich, deep soil is appreciated but not necessary. South of Philadelphia, even heavier shade—or, perhaps, just a couple of hours of morning sun then full shade the rest of the day—would be better. In colder climates, full sun is fine; my garden in southern New England seems safely north the full-sun-is-swell boundary: My pillar of climbing hydrangea is going gangbusters but receives no shade whatsoever, nor any supplemental watering. In Zones 4 through 6, then, climbing hydrangea seems to enjoy shade and full sun both; in gardens in warmer and warmer portions of Zone 7, more and more shade is advisable.

How to handle it: The Basics.

Plant this very hardy shrub at almost any time the soil is workable from Fall through Spring. Because climbing hydrangea sends out roots all along its stems anyway, don't hesitate to plant at a deeper level than the shrub was growing in its nursery pot. This can be especially helpful in steadying a young plant; they are sometimes oddly floppy; yet, unless their stems can maintain their position without wobbling or being dislodged by breezes, they won't sense the support structure, produce their adhering rootlets, anchor themselves, and (finally) begin to grow rapidly. A wobbly climbing hydrangea is likely to remain smaller longer.

 

As usually available at a regular nursery or a big-box store, climbing hydrangea will be trained up on some sort of temporary support: a stake or two, or a roughly built and intentionally short-lived little trellis. This is as much or more to keep the growth confined within the footprint of the pot and, so, facilitate easy and space-efficient handling in the production nursery as it is (or should be) to guide you in how to orient your shrub when planting it. Unless your chosen location requires that your shrub grow only vertically, it's a relief to know that you'll get quicker coverage up that wall or over that rock outcropping by planting the shrub so that its stems are trained along the ground at the base of its intended support. Trying to train stems up onto a supporting structure is usually frustrating: They are brittle, plus those glue-on attachments you could mount on walls to hold them never hold for long. Thank goodness, then, that the speed of growth and firmness of attachment (and the two are directly related) of upwardly-spreading growth that arises directly from stems you've arrayed more-or-less horizontally at the base of the structure will usually far outpace that from stems that you've tried to affix upward, mistakenly, to speed things along.

 

First, gently release the stems from the pot's training supports—or, rather, keeping in mind the stems' bizarre brittleness, release the supports from the stems. Check that you have cut through all the ties. If the supports are bamboo stakes, release them from each other if they have been tied at the top. Then, you may be able to pull each of them upward to free it from the hydrangea growth. If your shrub has been grown on a training trellis or lattice, carefully cut through it again and again with loppers until small pieces of it can be slowly fished out from the hydrangea stems.

 

Then, see to what degree the now-free stems can be untangled and extended, but don't get greedy. Remember how brittle they are, and be ready to accept kinks and tangles.

 

Now you're ready to plant. There's a good reason, I'm sure, but the planting medium used in mass production of climbing hydrangea is usually sandy. But this makes the root ball supremely friable and outright crumbly, the last thing you want when installing a plant that resents root disturbance.

 

When planting climbing hydrangeas, then, always dig the hole fully first, and try to unpot the shrub nearby or even over the hole. As will become clear below, the entire unpotting-and-planting task can become fast-moving and fraught even in experienced hands. Make things easier by choosing the location of your hole so that, when fully planted, the entire shrub will be more or less on its side, stems and all. 

 

Now, to extracting the hydrangea from its nursery pot. Don't attempt to release the root ball by pulling on the stems; they are as likely to snap as the root ball is to disintegrate. Instead, holding the pot in your hand, tip the shrub on its side, just a bit lower than horizontal, so that the stems point gently downward atop your other hand. Then, give the pot a brief shake in hopes of encouraging the rootball to begin to slide out of the pot. No luck yet? Set the plant down, still on its side and cut through the (now) upper side of the pot with hand pruners, so there's more room in the pot to help the root mass release. Lift the pot up again, while still keeping it angled just a bit below horizontal, and provide another little jiggle to the nursery pot.

 

Eventually, the root mass will slide from the pot; with luck, you will be able to place your hand beneath the root mass as it emerges from the pot to support it. Let go of the now-empty pot; do this quickly because, for that second, you'll be supporting the root mass with just one hand. Now with both hands supporting the root ball, lower it gently into hole that (hooray!) is immediately at hand.

 

The shrub's stems will be more-or-less resting on the ground along the supporting structure. Take a moment to gently arrange the stems, with the goal is helping them find their most-comfortable positions resting directly on the ground, directly against the support, or both. It's likely that all of the stems will want to go in just the one direction, but if there's a flexible free-thinker among them that can be angled in the opposite direction, go for it. Now sprinkle soil amid and atop the stems; do this handful by handful, not by the shovel-full, so that soils fills in beneath and, eventually, atop these always-oddly-angling stems without snapping them. Soon, generous portions of the stems will have become steadied against the ground as well as supported by the mounded-up soil you've lovingly added.

 

Those portions of the stems that, thanks to you, now enjoy full contact with the soil will root into it and, in return, send up self-clinging side shoots all the more quickly. And because those shoots are arising from stems that have been held firmly in place by that same soil, they'll be able to attach all the more readily to the supporting structure—and, again, grow all the more quickly.

 

Now, go back and fill in the hole, at the bottom of which has been patiently resting the shrub's root ball. As always with climbing hydrangea, work gently and slowly. Mound the soil atop the root ball even higher than the surrounding grade: Climbing hydrangea is an equal-opportunity rooter, and portions of stems that are now buried will send them forth.

 

Water the shrub gently but thoroughly—including all along the horizontal stems that are semi-buried in soil. The soil along walls can be surprisingly dry, especially if the walls are part of a building that has overhanging roof eaves, and could prevent much of the rain from reaching the newly-planted hydrangea. Water as needed during the first growing season and, if needed, the second. When the shrub begins to send out eager, fast-growing climbing stems, that's the sign that it has rooted into the soil sufficiently. As long as it has been planted in decent soil, an established climbing hydrangea usually doesn't need supplemental irrigation.

 

Whew—and congratulations! Your climbing hydrangea is all set to enjoy a long life of ever-increasing beauty. If your chosen location will allow the shrub to grow freely, no further attention is needed. If you'd like to control or direct the growth, though, you'll want to consider the pruning and training tactics in "Another option," below: Unlike, say, Hydrangea paniculata or H. arborescens, whose flower clusters are produced at the tips of new wood formed entirely in the current growing season—and, hence, can be pruned to any extent in Spring but will flower profusely in Summer—pruning of H. anomala must be timed carefully in the current season to ensure flowering the next. 

How to handle: Another option—or six!

The dizzying range of shapes and overall sizes that a climbing hydrangea can be trained into are all achieved by pruning current growth and guiding new growth. Climbing hydrangea is a vigorous shrub that is happy to send out many shoots in all directions, so there will be no shortage of stems to make use of one way or another. If your near-term priority is strictly to form the shrub into your desired shape, you can prune at any time: Unless you are gardening in Zone 4—the lower limit of hardiness for climbing hydrangea—new growth that might be formed as a result will be hardy. Clip anything that is out of bounds, then, whenever the urge strikes.

 

If you'd like your climbing hydrangea to flower—whether in the course of its training or for the long term, after the shrub has assumed its desired size and form—then you need also to concern yourself with preserving some of the breastwood year to year. As in "Habit," above, flower clusters form at the tips from new growth arising only from already-established breastwood stems, not from tips of new growth that may have arisen directly from traveler stems that very same season. Moreover, that new growth itself must have arisen from vegetative buds formed in late Summer and Fall of the previous season. All flower clusters of climbing hydrangea are the direct result of actions you did or did not take the previous year and, even, the year before.

 

There are two enormous consequences to this reality. First, while you could prune at almost any time if your goal is production of more vegetative growth (either breastwood or traveler), if you want flowers, you must let breastwood stems emerge and then grow for a year or two before they can receive any pruning at all: They need to be mature enough to form vegetative buds that will, next season, form the shoots that bear the flower clusters. Plus, after a given breastwood stem has begun producing the desired flower clusters, the only way it will continue to do so and accept any pruning that doesn't reduce next-year's flower crop is if that pruning happens right after the flowers have peaked. This is usually in early July. Only then will be there enough time for resultant growth to mature sufficiently to produce the vegetative buds later that Summer that lead to flower clusters the following Summer.

 

This means that breastwood stems must be a couple of years old—and long—before they can flower and, so, they'll never be very compact no matter how carefully you time your pruning: There's still that additional breastwood growth needed this season if flowers are desired the next. And so—secondly—climbing hydrangea that is both trained and flowering can never be tightly or compactly shaped: The volume of breastwood needed to sustain regular flowering is too large and loose. And yet, the appeal of the shrub's leafless branch architecture and exfoliating bark is so enormous, as is the plant's amenability to being trained intricately and densely that, as long as you have a second climbing hydrangea you can allow to grow into voluptuous flowering size, you could train the first into a triumph—albeit a non-flowering one—of tight geometry, expansive dimension and, clearly, dedication.

 

The growth of traveler stems presents its own oddities and opportunities. Overall, the very stems that you want the most when establishing climbing hydrangea either as a trained or free-range specimen are those that are growing quickly and have affixed themselves the most securely to the supporting structure. These nicely elongating stems can help your specimen's chosen form and size take shape all the more quickly, and then hold that shape indefinitely. But there's a connection between their speed of growth and their holdfast-roots' grip on the structure: The strength of the connection is, in part, what stimulates growth.

 

Further, holdfast roots form promptly along the bottom edge of tip growth or new side stems emerging from any traveler stem that has succeeded in anchoring itself. (In contrast, when a traveler grows beyond the bounds of its support, it is exploring in free space for additional support to attach to. There's no point in using energy to form holdfast roots when there's not yet anything to hold onto.) So, very little of the new growth from well-attached travelers is ever unattached—or potentially able to be directed easily in a more optimal direction. Then, add in the always-fearsome brittleness of this shrub's growth, whether young or old, slender or thick. You may be able to insert a knife between the stem and the plane of its support and use it like a letter opener to sever the connection between the two. But you're liable to slice through the stem as you work, or the now-freed portion of the stem will move so much that it fractures its connection to the still-afixed portions below. The reality, then, is that the traveler-stem portions of climbing hydrangea can rarely be repositioned even slightly.

 

To encourage growth where you want it and (to a degree) discourage it where you don't, you'll want to take advantage of this reality of holdfast formation: The more quickly holdfast roots can penetrate the surface of the supporting structure that also leads at least a bit upward as well as into stronger sunlight, the more readily the structure will be "colonized" by new traveler growth—and vice versa. Although climbing hydrangea is surprisingly shade-tolerant, it would be difficult to train stems downward or into areas of increasing shade. If climbing hydrangea is supposed to cover a large area where some spots are sunnier and others shadier, see if you can site the shrub in the spot that is the lowest and shadiest, to guarantee coverage there. It will inevitably find its way into the higher and sunnier portions.

 

For years, I thought I could train my pillar of climbing hydrangea directly up its supporting pole, which was galvanized pipe. No matter that I tied the shrub snugly to the pole, the stems failed to produce the holdfast roots—and, therefore, failed to elongated. Unintentionally, I had figured out how to inhibit my climbing hydrangea from climbing: provide only smooth and impervious surfaces.

 

Finally, one Spring I had the thought to surface the pole in cheap, soft wood. I cut the ties that were holding the hydrangea to the pole and inserted between the two a quartet of long strips of untreated pine. In effect, I had boxed the pole in with softwood lumber. I retied the hydrangea to the pine boxing, and marvelled that traveler stems began forming that same season. In two years, they had raced to the top of the pole while also sending out plenty of the breastwood stems that, the next year, began to bear flower clusters.

 

In the process, I had discovered the alpha and omega of climbing hydrangea's climbing surfaces: The most favorable are untreated lumber and the bark of lumber that is still "on the hoof" as part of a living tree. (Painted wood can also be colonized, but I wonder if some of it could be toxic.) As I proved, the worst was smooth metal; I bet glass and polished stone are lousy, too. In the middle is natural-surface masonry: bricks and concrete block, ledge and rocks, and cut but unpolished  stone such as granite, brownstone, and bluestone.

 

While climbing hydrangea is capable of sending out stems in all directions, the ones that discover the preferred climbing surfaces will grow the fastest. To have climbing hydrangea grow where you want, then, provide a surface of lumber or rough-textured masonry where you want the growth to go. If you use wood to form these guides, it will usually be in the forms of strips, perhaps like my inexpensive pine 1X4 boards, that you fasten onto, or tie to, the permanent support structure. Masonry guides would be permanent, of course.

 

Consider climbing hydrangea for a masonry wall that has coping or molding around windows or doors that is rougher-surfaced than the stone of the wall. It's also the case that any change in angle alone can provide encouragement to traveling hydrangea stems: Even if that molding or coping is the very same surface as the rest of the masonry, because the molding or coping projects outward from the wall, the angle between the two could provide sufficient footing. Perhaps you'll have the opportunity to specify a wall that includes a raised masonry course just for the purpose of providing anchorage for climbing hydrangea.

 

It was easy for me to transform my "uninhabitable" galvanized pole into something that climbing hydrangea would love: I tied the quartet of pine 1X4s around it with clothesline. If you are training climbing hydrangea into a specific pattern on a wall—around a door or window, say—fasten the boards to the wall with masonry screws. As the young stems root more and more deeply into the board, their rate of growth with maximize, as will their rate of thickening into the impressive shaggy-barked trunks that make this climbing shrub so remarkable in maturity. Note that all of this rooting-in also facilitates rotting of the training boards. Don't depend on the mature hydrangea's ability to maintain a secure grip on the underlying wall or the arms of metal scaffolding as these training guides begin to disintegrate. Loosely tie trunks to the underlying scaffolding (my galvanized pipe, e.g.), or to occasional anchor bolts installed directly into the the masonry. Over the years, the training boards will rot away entirely.

 

To increase the density of vegetative growth of your trained climbing hydrangea, as well as keep its three-dimensional volume to a minimum, you could prune all breastwood stems back to six or eight inches in the Fall. The leafless branches will maintain a clean profile until Spring. If needed, pinch new growth back in mid-June, too. Note that these prunings would preclude all flowering, in that they remove the late-season vegetative buds that could mature to flowering stems the following Summer. But the smart and tight display of branches and overall geometry are both maximized.

 

There are hybrid choices that combine creation of dense and compact vegetative growth with the longer and informal breastwood stems needed for flowering. The easiest would be to do such radical pruning only every third (or fourth) year. The second year after pruning, breastwood growth will still be non-flowering, but it will be fuller and more informal. The third (and fourth) year, the breastwood should be able to flower as usual in early Summer. A radical cut-back in Fall starts the cycle over.

 

Another hybrid choice is to prune so that some of the hydrangea remains tight, compact, and vegetative, while another portion is allowed to grow freely and bulkily so that it can flower. Say that you had trained climbing hydrangea up both sides of a doorway and across the top. Keep the sides trimmed and tight but let the top grow wild and full—and flowery. Train the top portion high enough above the door so that the breastwood doesn't billow down into the doorway opening itself.

 

Another option is to train climbing hydrangea up a sturdy pole while pruning to keep the growth around the middle and lower portions of the pole tight and dense. But let the growth at the top foot or two of the pole grow wide, high, and wild—and flowering. You'll have created a huge standard of climbing hydrangea, whose head might be six feet across. With this ultimate dimension in mind, be sure that the supporting pole is at least eight feet high.

 

Regardless of your choice in handling the breastwood, traveler stems from both the traveler's tip and all along its sides will still grow beyond your specimen's alloted space and dimensions. If these young stems can sense additional supporting structure—the wider masonry wall surrounding the arch of climbing hydrangea you've trained over your doorway, say—they'll try to make a break for it, attaching themselves every inch of the way. Once a year, go around the perimeter of the climbing hydrangea to sever these out-of-bounds stems and, as needed, lift the cut-off but still self-attached sections from the masonry with a putty knife, or—on permanent loan from your kitchen—a raised spatula or metal bench scraper.

 

These factors synergize to suggest even wilder training options: the potential size of a climbing hydrangea is nearly limitless, the lifespan of a given shrub is seemingly forever, established shrubs grow quickly, and thick old growth is even more remarkable than the younger. If you have the means to create enormous training opportunities for a climbing hydrangea, the shrub will cooperate:

 

What about installing a series of tall "pine-boxed" poles—ten feet seems the minimum, but then again, I'm fairly tall myself—spaced six feet apart? Climbing hydrangea could quickly ascend them all, creating a free-standing screen or, if you keep majority of side growth clothing each pole pruned tightly, a free-standing series of standards. 

 

What about arraying those poles in a circle or rectangle, then connecting their tops with cross-beams? Climbing hydrangea would eventually cover the horizontal poles, too, creating a shady pergola or Summer house. This would be advisable only in Zone 6 and colder, where climbing hydrangea seems to thrive in full sun as well as shade. In Zone 7 and warmer, climbing hydrangea itself needs to be in the shade, not to provide it. I'll never forget seeing a small free-standing pergola, perhaps six feet across with a peaked turret-like top, entirely clothed in climbing hydrangea in Boston. The pergola was constructed of rough wood and, by the time the structure itself had rotted away, the hydrangea trunks were so thick that the entire thing was self-supporting.

 

What about training climbing hydrangea onto a brownstone, story after story? Keep one or two vertical trunks for "supply lines" but then train just the occasional stems horizontally to trace the molding around the windows. For easier maintenance, allow breastwood just along the sill of each window. You would have achieved the effect of windowbox after windowbox, but you won't ever have to water them, or replant them seasonally.

 

If you become comfortable with creating strong supporting structures that also allow installation of plenty of linear feet of softwood "training tracks," you might consider forming climbing hydrangea into a Belgian fence, or an espalier where the limbs are arrayed upward and outward from a central bottom point like ribs of a fan. Note that the striking inflexibility of the wood of climbing hydrangea would probably make it impossible to form an espalier of horizontal limbs: These are formed by temporarily growing-out the limbs at an upward angle (which stimulates growth; keeping most limbs horizontal often retards growth) then lowering all but the very tip to horizontal, then continuing to grow out the tip at an upward angle. There would be a lot of risk of stem fractures in attempting to lower portions of climbing hydrangea stems to the horizontal.

 

If you want the Belgian fence or espalier of climbing hydrangea to flower without completely obscuring the details of its geometry, you'll need to allow enough room between arms or rungs for the necessarily bulky breastwood. For a Belgian fence, each diamond-shaped rectangle might need to be six or even eight feet from corner to corner. For a fanned espalier, arms might need to be pruned just for vegetative growth until farther up their length, when they are four or five feet apart. This could mean that the espalier has many fewer arms than it might for, say, a pear or apple, or that it is much higher and wider.

Quirks and special cases

When it reaches the upper limits of available support, climbing hydrangea responds like climbing ivy does: It switches from vegetative growth (those traveler stems) to growth that is sexually mature and produces flowers (that breastwood). Climbing hydrangea that is racing up the trunk of a hundred-foot-tall tree, then, might not flower as quickly as climbing hydrangea that has only a ten-foot pole to climb. If flowering is your priority, provide support structures that are comparatively short—that eight- or ten-foot pole—or are wider than high, such as stone walls.   

Downsides

Climbing hydrangea is notoriously slow to establish; in my experience, vines can mull things over for a year and even two before much new growth is evident. But then, eager stems can lengthen by several feet a season, and in all directions. Gardeners who plant this shrub are often caught by surprise—pleasantly—that the youngster that they had somewhat forgotten about has—suddenly it seems—covered half the garage.

 

The traveling stems of climbing hydrangea are strikingly inflexible, and are likely to snap when you attempt to adjust them. Worse, the older and thicker they get, the more brittle they become. I write from multiple incidents that are still painful to recall even decades later. Stems of breastwood are less prone to such catastrophic and sudden failures—but, of course, they always arise from those more-brittle travelers. If you try a dramatic repositioning of breastwood, it might act like a wrench upon its originating traveler, and apply enough torque that the traveler stem splits. And because the wood is so brittle, such a split is noisy. The "crack" is awful to hear. Don't attempt radical repositionings of any climbing hydrangea growth you can't afford to lose. Instead, try tactics that are more gentle as well as more strategic, that encourage growth to grow where you want it right from the start. See the second "How to handle it" box, above.

 

Climbing hydrangea breastwood can become two to four feet deep or more, and could become weighed down with considerable poundage of heavy snow or ice. A specimen growing up a pole, like mine, is at minimal risk because weight is distributed evenly around the support. The worst that might happen is that a couple of limbs of breastwood crack and need to be cut off; others will take their place quickly. Climbing hydrangea growing atop walls is similarly safe: the weight of the snow and ice simply presses the stems more tightly down onto the upper surface of the wall. But climbing hydrangea growing entirely on a vertical wall surface could be at risk of major detachment. Be sure that the main trunks are loosely tied every three or four feet to serious masonry bolts.

Variants

For a vine that is universally admired and, hence, has been grown by the millions in the West as well as East for many decades if not centuries, there are shockingly few variants. Plus, two of them, 'Miranda' and 'Firefly', which were introduced independently and originated on opposite sides of North America, are indistinguishable. With the enduring and well-deserved popularity of the petiolaris subspecies, we can assume that this shortage of cultivars is not from lack of adoring observation from all of those fans but, rather, that the vine is very stable genetically, and mutates only rarely.

 

The leaves of 'Miranda' are notably smaller, as well as so showily margined in yellow that the vine's typical flowers are almost secondary. It is much slower than the straight petiolaris, especially when young. It's also likely to be much smaller at maturity. I live in hope that, perhaps in its second decade, mine will finally have explored the entire front of a seven-foot stone. 'Miranda' (originally spelled 'Mirranda') was named for their daughter by Guy and Jeannie Meacham of Rippingale Nursery, in Boring, Oregon. (See its bright foliage in the bottom pictures of this post.) 'Miranda' is reported as being indistinguishable from 'Firefly', even though that cultivar arose at Chanticleer Gardens, in Wayne, PA.

 

Foliage of 'Winter Surprise' turns burgundy in the Winter. This evergreen cultivar is likely to be less hardy than the straight petiolaris subspecies and, to my knowledge, is not yet available in North America. Foliage of 'Silver Lining' is noticeably slate blue-green in comparison to the bright green leaves of the straight petiolaris subspecies. They are also edged with creamy white edge. This cultivar looks stunning but doesn't seem available in North America yet. Foliage of 'Kuga Variegated' (also known as 'Moonlight Magic') is heavily splashed with cream, and the youngest stems are pink. I have not been successful in establishing this cultivar despite trying twice. My guess is that it is less hardy outright, or less tolerant of moisture in Winter, or less tolerant of heat in Summer.

The sterile flowers of 'Skylands Giant' are reported as being larger than those of petiolaris, and the vine is supposed to begin flowering at a younger age.

Availability

Online as well as at retailers.

Propagation

By layering. Because older stems are notoriously brittle, in early Spring look among the first-year growth of last season for a slender stem that is low enough, long enough, and flexible enough for you to bring it into contact with the soil. You'll want to cover a portion of it as far away as possible from the tip with soil, so that the free end of the stem isn't stubbing into the ground but, rather, can climb outward and upward at will. Set a brick across the soil-covered stem both to hold it down (if needed) and also to keep rain from washing the soil away. If possible, tap a thick stake into the ground near the covered-with-soil section, and tie the tip-portion of the stem as closely to it as you can without snapping it: Stems that feel the presence of a plausible climbing structure can grow much faster. If you're lucky, you'll have been able to position the stake vertically, but the length of the stem tip or the limit of its flexibility might not permit that. If you've needed to set the stake at an angle, secure it by pounding in a vertical support stake, and tie the two together.

 

Allow the stem to grow for the season or even two. If you see that it has begun to grow more quickly, this likely means that it has "found" the stake and has sent out climbing roots to adhere to it. This is also likely to mean that the soil-covered section has produced roots as well: the ones that will penetrate the soil and enable the thriving stem to survive on its own. Early the following Spring, remove the brick, sever the now-rooted stem from the mother plant and gently transplant to the new location. Take heart in remembering that Hydrangea anomala subsp. petiolaris dislikes root disturbance, so your transplant will probably not grow much for the next year or even two. That's fine: The goal isn't growth per se, but establishment. As long as the young transplant is producing foliage and sustaining itself, that means you've succeeded.

 

Counterintuitively for a woody plant whose stems are so prolific in production of holdfast roots, cuttings of climbing hydrangea are reported to be challenging to root. Harvest them in late Spring or early Summer, while they are still green.

Native habitat

Hydrangea anomala subsp. petiolaris is native to Japan and Korea. The straight species, Hydrangea anomala, and its variant H. anomala subsp. anomala are native to the Himalaya and western China; they are a bit less hardy—to Zone 5, not 4—and their flower clusters are considered to be somewhat less showy. In cultivation, climbing hydrangea is nearly always the petiolaris subspecies.

 
 
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