The climbing hydrangea is a deciduous vine from the woodlands of Japan, Korea and Siberia, where it grows up trees and across rock faces. It has small aerial roots on the stems that help it cling on, though in the garden it is not as reliably self-supporting as some other climbers, so it is generally given additional help with wires and plant ties.
Newly planted specimens can be a little slow to get going and often make little growth in the first few years. However, once it has established a good root base, it will start to spread more rapidly, climbing up to heights of 15 metres or more, and it is generally fairly low-maintenance. The main quality of the climbing hydrangea in the garden is that it prefers the sort of shaded spot that can otherwise be difficult to plant. It is very much at home spreading across north-facing walls. It can also be grown as ground cover in a shaded woodland garden, where it will eventually grow over an area of 20 square metres.
The climbing hydrangea has glossy lime-green leaves with a heart-shaped base that turn gradually bright buttery yellow in autumn before falling, and exposing the attractive coppery brown stems. It bears 25cm diameter flattened heads of lacy flowers in the summer. The fertile flowers are small and an inconspicuous greeny-white, but the heads also include some much showier and larger sterile flowers that have creamy white petals. Once growing well, the climber will be covered in these frothy flower heads for much of the summer.
This article provides information on caring for this very useful and attractive climber.
Sometimes known simply as Hydrangea petiolaris, this climbing hydrangea has been awarded the prestigious Award of Garden Merit by the Royal Horticultural Society for its qualities as a garden plant. This is the typical climbing hydrangea that can be bought from large garden centres and nurseries. It can be trained up walls with northern, southern, eastern or western aspects, though does best in dappled or full shade.
A few cultivars and hybrids are also available, though generally only from specialist nurseries.
Hydrangea anomala subsp. petiolaris ‘Mirranda’
‘Mirranda’ is a vigorous, deciduous climber, and can grow up to 18m tall in ideal conditions against a north-facing wall. It differs from the species by having foliage with irregular golden-yellow edges and variegation that fades to a creamy white colour as the year progresses. The peeling brown mature bark is revealed after leaf fall in the autumn. It has large domed clusters of showy white flowers through the summer.
As its name suggests, ‘Silver Lining’ has silver-edged variegation to its greyish-green leaves.
This evergreen climbing hydrangea species from Mexico is less commonly grown in the UK as it is not fully hardy, and will not tolerate more than a couple of degrees of frost. It grows to 12m tall, and enjoys similar soil conditions and growing positions to Hydrangea anomala subsp. petiolaris. Being evergreen, it provides year-round colour against a wall, and if a suitably protected and sheltered position can be found in the less frost-prone parts of the UK, it may be worth trying. However, if there is any doubt about conditions being suitable, the next variety is a safer bet.
‘Semiola’ is a hybrid between Hydrangeaseemanii and H. petiolaris. It has inherited the hardiness and free-flowering nature of H. petiolaris, and the evergreen habit of H. seemanii, with leaves that start out as a coppery colour and later turn light green with age. Thus it has the best of both worlds, making it a very attractive, floriferous, semi-evergreen climbing hydrangea that thrives in shade, and perfect for a north-facing wall. It will grow in any well-drained soil, and performs best in dappled shade. It also makes an excellent ground cover plant in shaded areas.
Climbing Hydrangea Care
Climbing hydrangeas are quite slow growing, especially in a cold and always shaded position, but once established they will develop over 10 to 20 years to a height of up to 15 metres with an ultimate spread of between 4 metres and 8 metres. The ideal spot to plant them is against sound masonry walls or on very sturdy trellises or fences that are expected to last for many years. Without additional support they can sometimes come away from the frame, so to avoid disasters later on in the life of the climber when it has become top heavy, it is advisable to use training wires and plant ties form the outset, and to add more as necessary as the plant grows.
Climbing hydrangeas like to have their roots in moist (though never waterlogged) soil, and a good mulch of well rotted garden compost or other organic material every winter will help to keep moisture in the soil during warmer weather and also provide an annual boost of nutrients.
They will survive in all types of sunny and shady conditions, and many enthusiasts suggest that they have a preference for early morning sun and midday and afternoon partial or full shade. They are one of the few flowering climbers that will tolerate dense shade and keep flowering, indeed the flowers on plants grown in the shade seem to last longer than those on plants grown in the sun. Climbers grown in sunnier locations will need greater attention to soil moisture, and a regular mulch to shade and cool the base of the plant and the roots is beneficial.
Following planting, it is important that the climber is not allowed to dry out. It should be well watered in, and a suitable mulch applied to retain the moisture. The plant should be watered weekly in its first summer in the garden, or more frequently in very dry weather, until it is established.
While the climbing hydrangea is best suited to growing in a soil with moisture-retaining properties and good internal drainage, it is a relatively tough plant once established and it will survive in almost any type of garden soil, provided it is not waterlogged. Its preference is for a well-drained and light loamy or sandy soil, either neutral or slightly acidic, though it will tolerate mild alkalinity. These conditions can be promoted through the regular application of well-rotted manure, leaf mould or good garden compost.
Climbing hydrangea plants do not generally need much feeding once established, especially if they are given regular dressings of organic compost as this will improve soil fertility as well as its structure and moisture-retaining capacity. On particularly poor, light sandy soils they may benefit from an annual feed in late winter or spring with a general purpose fertiliser, but too much feeding will produce leafy growth at the expense of flower buds. It will also make the plant more susceptible to frost damage in very colder winters. Overall, it is better to err on the side of caution and to underfeed rather than overfeed.
Climbing hydrangeas do not require routine pruning, and they can generally be kept tidy and in shape simply by removing dead flower heads and trimming any unwanted shoots back to some healthy buds. If a flatter espalier that sits more tightly against the wall is desired, outward-facing side shoots can be pruned back to a pair of buds.
Always use sharp secateurs to make clean cuts and to avoid crushing the stems. Wipe the blades carefully with rubbing alcohol before trimming the plant to reduce the risk of introducing disease.
Newly planted climbing hydrangeas need time to grow adequate roots and to settle into their new position before any pruning is done. Early pruning will divert energy from root development and produce a weaker plant, so they should not be pruned in the first two years after planting.
Once it is established, it is possible to carry out a minor trim of the climber after flowering in late summer. At this time the vine can be trimmed back to maintain it within its allocated wall space, to control its height or spread, or to prevent it from growing across windows, doors or gates. For this minor pruning, no more than one third of the plant’s growth should be removed. If a more radical prune is necessary, wait until the vine is dormant to reduce stress. Cuts should be made just above leaf nodes to encourage the remaining plant to fill out. Any dead branches should also be removed.
The flowers are produced on the previous year’s growth, so if it is pruned before flowering there will be no blooms for that year.
A mature plant that has not been supported properly can sometimes get blown down in the wind, especially if it has become spindly and top-heavy. If it is damaged and cannot be easily refastened to the supporting wall, it may be better to undertake a heavy restorative pruning. Healthy vines will rejuvenate, but if possible wait until the plant is emerging from dormancy in the late winter or spring before carrying out the major pruning. Prune away the majority of the plant, leaving just three to five 1 metre high stems. It will regrow, but it should not be pruned again for at least a couple of years.
Climbing Hydrangea Propagation
Climbing hydrangeas are easy to grow from softwood, semi-ripe or hardwood cuttings at any time between May and August, but the easiest and most successful propagation technique is layering. Unlike cuttings, which suffer the stress of being removed from the parent plant and need to survive until they have produced their own roots and leaves, layered shoots are encouraged to form roots while still attached to the parent plant, and are thus being constantly supplied with water and nutrients whilst developing.
Layering can be carried out in autumn or spring, but they are unlikely to root if the soil is dry, so spring layers in particular should be kept well watered in dry spells. The fresh new growth developing from layered plants is particularly attractive to slugs and snails, so if being done at ground level, precautions and protection may be necessary.
Common Climbing Hydrangea Problems
Hydrangea scale became established in the UK during the 1980s and has since become widespread in English gardens. It is a sap-sucking insect that is typically first noticed as masses of eggs covered in white waxy fibres that form smooth, oval patches some 3mm to 4mm in diameter on the stems and foliage in the summer. The patches persist on the plant after the eggs have hatched. Badly infested plants suffer a reduction in vigour as the insect sucks sap from the foliage and stems. It can also lead to leaf loss.
Once hydrangea scale is established, manual removal of egg masses and adult insects is unlikely to be effective, so it may be necessary to control the outbreak with an appropriate insecticide spray outside the flowering season. If spraying is successful, the dead scale insects will remain firmly attached to the plants, so the degree of success of the treatment can only be properly judged in the following spring when it will be apparent if the new growth is free of infestation.
Climbing hydrangeas can also suffer from vine weevil, and the root balls of plants from garden centres should be checked for larval damage before buying. While the larvae will eat the plant’s roots, the adult weevils will cause damage to the leaves in the form of small, regular bites taken from the leaf edges, particularly near ground level.
Red spider mites and capsid bugs may also cause some minor damage to the plants, particularly if they are stressed in other ways.
Climbing hydrangeas rarely suffer from diseases though they can occasionally show signs of fungal or viral infection. Good ventilation and garden hygiene should keep any attacks by grey mould (Botrytis), powdery mildew or leaf spot in check.
Q Layering sounds like a good way to make some new climbing hydrangea plants. How do I go about it?
There are several methods of layering. ‘French’ layering and ‘tip’ layering do not work well with climbing hydrangea, so go for the ‘simple’ or ‘serpentine’ layering techniques.
Simple layering works well for any shrubs or climbers with shoots that can be bent down to ground level. The flexibility of climbing hydrangea makes it ideal, especially plants that are grown as ground cover. Always select flexible young shoots on the outside of the plant that can be bent easily down to the ground. Mark the point where you want to ground the stem with a bamboo cane. About 30cm from the shoot tip, make a 2.5cm to 5cm incision along the stem, running through a leaf bud from which the leaf has been removed. Prop open the cut by wedging a small piece of wood into it, and apply hormone rooting powder to the surfaces of the wound.
Make a shallow trench about 12cm deep in the soil from the marker bamboo cane back to the parent plant and peg the prepared stem into the trench with a loop of thick wire or a tent peg. Bend the tip of the shoot up and secure it with twine to the marker cane, so that it is growing upwards. Back-fill the trench with soil and water well. Keep the area moist, especially in dry weather.
It may take up to a year for roots to fully develop, and the area must be kept weed-free and tended over that time. When it is clear that a good root system has formed, cut the stem to release the new plant from the parent, and transplant it into its final position. It is also possible to layer into a prepared pot of compost rather then into the ground. This will require more watering, but will have the advantage of being easier to care for than a patch of open ground, and once the new plant has been severed from the parent, it can be grown on in the pot for a while until the roots are fully established.
Serpentine layering is a very similar process, but it involves looping the chosen stem in and out of the soil to encourage roots to form at several points. The technique for each buried section is the same as that for simple layering.
Q I am lucky enough to have a small walled garden that I am developing into a wildlife garden. There is a long north-facing wall that will be ideal for a climbing hydrangea, but I am not sure if it has any good wildlife qualities?
As you say, a climbing hydrangea will be ideal for this situation, where it would be difficult to get much else to grow effectively. Happily, climbing hydrangeas are great for wildlife. Although it will take a few years to grow large and thick enough for nesting birds, it will eventually get there, and provide ideal sheltered and secure nooks and crannies for nesting song birds like blackbirds and robins. In turn they will help to keep your garden pests under control. The flowers are also very attractive to pollinators, so on warm summer days they will help to attract bees and butterflies to what might otherwise be a rather sterile and dark part of the garden from a wildlife perspective.