Plant taxonomy classifies climbing hydrangeas as Hydrangea anomala ssp. petiolaris. This is a case where the Latin name (Hydrangea) is so commonly used that it essentially doubles as a common name. When used as a common name below, it is not capitalized. Technically, you could also call them climbing "hortensias" (an old common name), but relatively few people use that name today.
Qualities of the Plant
Climbing hydrangea vines are large plants, sometimes reaching 50 feet tall or more at maturity. In early summer, they produce fragrant, lacy ("lace-cap"), flat-topped, white flower heads. These lace caps can be 5 inches or more in width and are composed of showy flowers on the outside and less-than-showy flowers on the inside. When they dry out, these flower heads turn reddish brown. Some gardeners cut off the dried flower heads for use in crafts.
The leaves, which are medium-green in color during the summer, turn yellowish in autumn. But these plants are not grown for their fall-foliage color. The plants' peeling bark gives you good winter interest.
Planting Zones, Sun and Soil Requirements
Native to the Far East, climbing hydrangea vines are best grown in planting zones 4-7.
Relatively few hardy flowering vines tolerate shade. Climbing hydrangea plants are one of them. In fact, in hot climates, they actually prefer a location with at least partial shade. Elsewhere, they will do all right in more sunny areas, usually, if watered. Keep the soil evenly moist. Apply a 3-inch layer of mulch to help retain water in the ground around the root zone. Climbing hydrangeas that do get more sun tend to bloom better. The soil should be well-drained and contain plenty of compost. Aim for a soil pH that is slightly acidic.
Grow climbing hydrangea vines up trees (see below if you have concerns for the safety of your tree), garden arbors, trellises, pergolas, and fences. Because the vines become so large (and, therefore, heavy) over time, be sure that whichever support you use is sturdy. The plants can also be pruned and maintained in shrub form.
Yet another use for them is as ground covers. Where their suckers make contact with the ground, they will take root. This gives the plant the chance to spread and fill in an area, cutting down on weed growth there. Make use of their white flowers in moon gardens. Their tolerance for shade gives many of us much-needed flexibility in developing our landscape designs. They are also salt-tolerant plants, making them valued in seaside communities.
Concerns About Climbing Hydrangeas: Walls, Trees
There is some debate as to whether owners of brick homes should allow climbing hydrangeas to climb up their walls (or whether you should allow them to grow on chimneys). The most widely-held opinion seems to be that they are safe for brick surfaces, as long as the mortar is in good shape.
But that does not really solve the problem. After a mature vine has covered such a surface and cracks develop in the mortar, how are you going to be able to get at the mortar in order to repair it? The vines will be in your way. In fact, they may hide the surface so completely that you fail to detect the cracked mortar at all.
More generally, the problem with growing a vine such as climbing hydrangea upon a house wall is that it will eventually get into areas where you do not want it, such as gutters. Sure, you can keep it pruned so as to avoid this, but do you want to be climbing high up on a ladder to execute such a task? Most people are trying to reduce their landscape maintenance tasks, not add to them.
So much for the safety issue regarding brick surfaces. In terms of how they affect the appearance of brick, you will read conflicting reports as to whether the holdfasts of climbing hydrangeas will stain brick walls. If you want to stay on the safe side, simply avoid growing them on brick walls. While the wisdom of growing them on brick walls is debatable, there is no debate regarding growing them on surfaces other than brick. Definitely do not permit them to climb houses sided with shakes, clapboards, or vinyl. They will cause damage to these types of surfaces.
But do they cause harm to trees? "Frequently concern is expressed about climbing vines that may be inundating a tree and causing irreparable damage: there has never been a proven case of damage occurring from climbing hydrangea, however," reports the Cornell Cooperative Extension, citing Richard Weir.
Climbing hydrangeas solve a problem for homeowners with shady areas to plant. Even though they will not flower as much if planted in full shade, these shade-tolerant vines provide you with the choice of growing a plant with attractive foliage and interesting bark in areas that have too much shade for many other plants. Another nice feature is that, due to their large size, they can cover quite an area once they mature.
Care for Climbing Hydrangea Vines
Newly planted climbing hydrangea vines are slow to grow and slow to bloom. But there is not much you can do about it, other than to start out with the largest plants possible (of course, you will pay extra at the garden center for larger plants). As for pruning in later years, one Master Gardener writes that once the plants are established, "they can grow quite vigorously and may need occasional summer pruning to stay in bounds."
Few pests or diseases trouble this plant. For example, it is rabbit-proof.
The Greek root hydr- in the name, hydrangea refers to water, as in "hydroelectric," "hydroponics," "hydration," etc. Meanwhile, angeon comes from the Greek for "vessel." So in what way are they like a "water vessel?" Most species of hydrangea require a lot of water, thus earning the plants this watery name.