Plant problems

Why Are My Pileostegia Leaves Curling?

Q: Why are my pileostegia leaves curling?

Pileostegia viburnoides (evergreen climbing hydrangea) leaves curl most commonly in UK gardens because of drought stress (the large, leathery, evergreen leaves curl inward along their length and the margins brown when the root zone dries out in summer), cold damage in hard UK winters (the evergreen leaves curl and develop brown patches after hard frost or cold drying wind), or establishment stress in the first two to four seasons after planting (pileostegia, like its relative schizophragma, is slow to establish and can wilt and curl its leaves during this phase). Pileostegia viburnoides is a self-clinging, evergreen climbing shrub from China, Japan, and Taiwan; it climbs by aerial rootlets attached directly to rough surfaces and is closely related to Hydrangea petiolaris and Schizophragma hydrangeoides, though unlike those species it is fully evergreen. It produces large, flat-topped or domed heads of small, creamy-white, four-petalled flowers in late summer (August to September or October), which are very attractive to bees and other pollinators; the flower heads are made up entirely of small fertile flowers (unlike hydrangea and schizophragma which have sterile outer florets), giving a frothy, cream-coloured effect over the dark, glossy evergreen leaves. The plant is valuable in UK gardens as one of the very few self-clinging evergreen climbers hardy enough for general outdoor use; it is exceptionally shade-tolerant and one of the best climbers for dark, north-facing walls and heavily shaded positions where few other flowering climbers succeed.

Q: Is pileostegia hardy in the UK?

Pileostegia viburnoides is hardy to approximately -10 to -15°C in sheltered conditions and is reliably perennial in most of England, Wales, and sheltered positions in Scotland and Ireland. It is significantly hardier than many other evergreen climbers (hardier than trachelospermum in most UK gardens, for example) and is grown successfully in a wide range of UK gardens including some quite cold positions. The large, leathery, evergreen leaves may be damaged or partially shed in hard winters below about -12°C, but the plant typically regrows from surviving wood in spring; total plant death from cold alone is uncommon in most UK conditions. Cold wind causes desiccation of the evergreen leaves and can produce browning and curling similar to frost damage; a position on a north or east-facing wall that is sheltered from the coldest winds is generally more successful than an exposed position. The plant is self-clinging and eventually covers its climbing surface with a dense, dark, evergreen cover of glossy leaves; against a north-facing wall in a UK garden, an established pileostegia provides excellent year-round coverage of the wall. The slow establishment period (similar to other self-clinging hydrangea-family climbers) means the plant requires patience in its first few seasons, but once established it is vigorous, largely self-reliant, and long-lived.

Q: How do I grow pileostegia in the UK?

Pileostegia viburnoides grows in any aspect from full sun to deep shade, on any rough-textured climbing surface (brick, stone, rough timber; it cannot cling to smooth surfaces), in moist, fertile, humus-rich, well-drained soil. It is one of the most adaptable and versatile self-clinging climbers for UK gardens; the north or east-facing wall in moist soil is the position where pileostegia excels most clearly over the competition, as few other self-clinging flowering evergreen climbers are reliably hardy in such positions. Plant in spring (April to May) and water consistently throughout the first two to three growing seasons; drought stress during establishment both slows root development and causes the leaf curl and wilting that discourages gardeners into thinking the plant has failed. Mulch the root zone with 10 cm of composted bark every spring; the mulch conserves moisture and maintains the humus-rich root environment the plant prefers. Feed with a balanced fertiliser in April in the first two years. Once established, pileostegia is largely self-reliant; it can be pruned in spring (March to April) to control size if it outgrows its space, cutting stems back to healthy buds; like all climbers in the hydrangea family, it flowers on the current and previous season's wood, and the pruning should be light to avoid removing all the flowering wood. The plant is slow to begin flowering; most established UK plants begin producing their creamy-white flower heads from year four or five, and the display improves as the plant matures. In deep shade, pileostegia flowers less abundantly than in a brighter position; full sun to partial shade produces the most flowers, but the plant is genuinely usable in quite deep shade.

Q: How is pileostegia different from climbing hydrangea?

Pileostegia viburnoides, Hydrangea petiolaris (climbing hydrangea), and schizophragma are all self-clinging climbers from the hydrangea family (Hydrangeaceae) that attach by aerial rootlets and produce flat or domed flower heads in summer; they have similar cultural requirements and the same famously slow establishment period. The key distinctions are: pileostegia is fully evergreen (the others are deciduous), making it uniquely valuable for year-round wall coverage and for winter garden interest; pileostegia flowers in late summer (August to October), later than climbing hydrangea (June to July) and schizophragma (July to August); pileostegia has flower heads made entirely of fertile flowers with no showy sterile florets, producing a creamy-white frothy effect that is attractive and distinctive but less showy than the lace-cap effect of climbing hydrangea or schizophragma; pileostegia has larger, more leathery, more prominently veined leaves than climbing hydrangea. The evergreen character of pileostegia is its most significant garden advantage over its deciduous relatives: it provides continuous leaf coverage of its climbing surface throughout the year and is a more effective screen for unsightly walls, fences, or structures. It is also exceptionally shade-tolerant, arguably the most shade-tolerant of the three, and is the best choice for north-facing walls and positions where year-round leaf coverage is more important than the most showy possible flower display.

Pileostegia viburnoides (evergreen climbing hydrangea) is one of the very few self-clinging evergreen climbers hardy enough for general UK use, with glossy, leathery leaves and creamy-white flower heads in August to October. It is exceptionally shade-tolerant and ideal for north-facing walls. Drought stress and cold damage are the most common causes of leaf curl; the plant shares the famous slow establishment period of its hydrangea-family relatives.

Drought stress

Drought stress is the most common cause of leaf curl in pileostegia in UK gardens, particularly in the first few seasons after planting and against warm south or west-facing walls where the soil base dries out rapidly in summer. The large, leathery, evergreen leaves curl inward along their length and the margins begin to brown and crisp when the root zone dries out; the plant looks under stress quickly in hot, dry conditions. Against a south-facing wall in summer, the soil can be very dry even in average UK conditions, and pileostegia in such positions needs more supplementary watering than the same plant on a cooler, moister north or east-facing wall.

What to do

Mulch the root zone deeply (10 cm of composted bark) every spring; extend the mulch to the drip line and renew annually. Water during dry spells; water thoroughly rather than shallowly to encourage deep root development. Newly planted pileostegia needs consistent moisture throughout its first two to three growing seasons. On south-facing walls, low ground-level planting around the base of the climber reduces soil temperature and moisture loss.

Cold damage

Cold damage browns and curls the evergreen leaves of pileostegia in hard UK winters; temperatures below about -12°C, and cold drying wind at any temperature, cause browning and inward curling of the leaf margins. Cold wind desiccates the large evergreen leaves as rapidly as hard frost; a position that is sheltered from prevailing cold winds (typically north and east winds in the UK) is important, though pileostegia is significantly hardier than many other evergreen climbers and is damaged less severely than trachelospermum, for example, in most UK winter conditions. The plant typically regrows well from surviving buds after a cold winter, though recovery growth may be slow to appear in spring.

What to do

Choose a position sheltered from north and east winds; a north or east-facing wall that is sheltered from direct cold wind (e.g. by a building return or adjacent wall) is ideal. Do not prune winter-damaged growth until April or May when new growth from surviving buds confirms the extent of damage. In colder UK areas, wrap young plants in horticultural fleece for their first two winters. Established plants recover well from moderate cold damage.

Establishment stress

Like its relatives climbing hydrangea and schizophragma, pileostegia is notoriously slow to establish; in its first one to three seasons after planting, the plant may produce little above-ground growth and its leaves may wilt and curl in conditions that would not stress an established plant. This is the plant investing in root development rather than top growth; the aerial rootlets may not begin attaching firmly to the climbing surface until the second or third season. Leaf curl and intermittent wilting during this establishment phase is normal and does not indicate that the plant is failing.

What to do

Maintain consistent soil moisture throughout the establishment period; this is the single most important factor in reducing establishment stress and the leaf curl associated with it. Do not prune, move, or disturb the plant during establishment. Be patient: growth and flowering begin properly from year three to five. An established pileostegia is vigorous, largely self-reliant, and long-lived; the investment of patience during establishment is repaid over many decades.

Frequently asked questions

Why are my pileostegia leaves curling?

Pileostegia leaves curl most commonly because of drought stress (the leathery evergreen leaves curl inward when the root zone dries out; mulch deeply and water during dry spells), cold damage in hard winters (leaf margins brown and curl after hard frost or cold drying wind; the plant recovers in spring), or establishment stress in newly planted specimens (slow establishment with intermittent wilting is normal; consistent moisture is the solution). It is significantly hardier than many other evergreen climbers.

Is pileostegia hardy in the UK?

Pileostegia is hardy to about -10 to -15°C in sheltered conditions and reliably perennial throughout most of England, Wales, and sheltered Scottish and Irish positions. The evergreen leaves may be partially damaged in hard winters but the plant regrows from surviving wood. Cold wind desiccates the leaves; shelter from north and east winds is more important than frost protection. It is significantly hardier than trachelospermum and among the hardiest evergreen self-clinging climbers for UK gardens.

How do I grow pileostegia in the UK?

Grow on any rough-textured surface in any aspect (full sun to deep shade) in moist, fertile, humus-rich, well-drained soil. Keep consistently moist for the first two to three seasons. Mulch 10 cm deep every spring. Prune lightly in spring if needed to control size. The north-facing wall in moist soil is where pileostegia most clearly outperforms alternatives; it covers the surface with glossy evergreen leaves year-round and flowers in August to October when few other climbers are in bloom.

How is pileostegia different from climbing hydrangea?

Pileostegia is fully evergreen (climbing hydrangea is deciduous), providing year-round wall coverage; it flowers in August to October (later than climbing hydrangea's June to July); it has flower heads made entirely of fertile flowers with no showy sterile florets, producing a creamy-white frothy effect; and it has larger, more leathery, more prominently veined leaves. The evergreen character and exceptional shade tolerance are pileostegia's greatest advantages over its deciduous relatives for north and east-facing walls.