Plant problems

Why Are My Corokia Leaves Curling?

Q: Why are my corokia leaves curling?

Corokia (wire-netting bush) leaves curl and drop most commonly in UK gardens because of cold damage in hard winters (most corokia species and cultivars are marginally hardy and the small, spoon-shaped, silver-backed leaves curl and drop in hard frost), drought stress in summer (the leaves curl inward along their length when the root zone dries out; the plant is drought-tolerant once established but can suffer in containers or in very hot, dry conditions), or waterlogging in wet soils (corokia requires freely draining conditions and its roots rot in persistently wet soil). Corokia is a genus of around three species of New Zealand evergreen shrubs with a highly distinctive divaricating (interlaced, zigzag, wiry) branching habit that gives the plants their common name 'wire-netting bush'; the dense, interlacing pattern of thin wiry branches creates an impenetrable, architectural tangle that is quite unlike any other commonly grown UK garden shrub. The most commonly grown species are: Corokia cotoneaster, with the most dramatically interlaced, wiry branches, tiny leaves, and small yellow star-shaped flowers followed by red or yellow berries; Corokia buddlejoides, a larger, more upright species with broader, longer leaves and a less extreme branching habit; and numerous hybrid cultivars, particularly Corokia x virgata cultivars including 'Bronze King' (bronze-purple leaves), 'Red Wonder' (green leaves, red berries), and 'Yellow Wonder' (yellow berries), which combine the distinctive habit with colourful berries and are among the most ornamental forms for UK garden use.

Q: Is corokia hardy in the UK?

Corokia hardiness in the UK depends on the species and cultivar; most Corokia x virgata cultivars (including 'Bronze King', 'Red Wonder', and 'Yellow Wonder') are considered the hardiest forms and are generally hardy to approximately -10 to -12°C in freely draining, sheltered conditions, making them reliable in most of southern and central England and Wales in suitable positions. Corokia cotoneaster is similar in hardiness. Corokia buddlejoides is less hardy (to about -5 to -8°C) and is more restricted to mild UK gardens. The divaricating, wiry branching habit of corokia is actually an adaptation for cold survival: in New Zealand's mountains, the divaricating shrubs protect their growing tips within a network of tough, flexible outer branches that deflect grazing animals and provide microclimate shelter from frost and wind; in UK gardens this same habit gives the inner parts of the plant some protection from moderate frost and makes the plants more resilient than their hardiness rating might suggest. Cold and wet combined is more damaging than cold alone; corokia in perfectly draining, lean soil survives significantly lower temperatures than in wet, heavy conditions. Coastal UK gardens and mild urban positions suit corokia well; it is a popular hedging and architectural shrub in coastal gardens in south-west England, Wales, and western Scotland.

Q: How do I grow corokia in the UK?

Corokia grows best in a sunny, sheltered position in full sun to light partial shade, in well-drained to freely draining, moderately fertile, neutral to slightly alkaline soil. The plants are tolerant of coastal conditions (salt wind, sandy or well-drained soils) and are particularly suited to UK coastal gardens where the combination of mild, maritime climate, freely draining soil, and salt wind actually suits their New Zealand coastal and open-country origins well. Corokia does not need rich, moist, or heavily improved soil; moderately fertile, well-drained soil produces the best growth, and lean to moderate conditions enhance the silver colour of the leaf undersides. Plant in spring (April to May) in a sheltered position. Prune in spring (April to May) to control size and maintain the plant's attractive architectural habit; corokia responds well to clipping and can be maintained as a low to medium informal or formal hedge. It is occasionally used as a low, clipped hedge in coastal UK gardens where it is reliably hardy; the divaricating habit creates an impenetrable, if informal, barrier. The colourful berries (red or yellow, depending on cultivar) are produced in autumn following the small yellow star-shaped flowers in spring; they are ornamental and persist on the plant for several weeks. In very cold UK areas, grow corokia in containers of free-draining compost and bring under glass from November to March.

Q: Why is my corokia losing its leaves?

Corokia is an evergreen shrub but may drop a proportion of its leaves in hard UK winters; this is a normal response to cold stress rather than necessarily a sign that the plant is dying. The small, spoon-shaped leaves curl and fall progressively in cold weather, and the wiry, bare-stemmed appearance of the plant in winter can cause concern among gardeners who have not grown it before. In most UK winters in a sheltered position, corokia retains the majority of its leaves; in hard winters it may drop more, but it typically regrows from the surviving buds and new growth appears from March onwards. More significant and concerning leaf loss accompanies root rot from waterlogging or very hard frost (below about -12°C); in these cases the stems may also blacken and collapse, and the plant may not recover. To assess the plant after a hard winter: scratch the bark of a stem with a fingernail; green tissue beneath the bark indicates the stem is alive; brown or dry tissue indicates it is dead. Check several stems at different heights from the base to understand the extent of the damage; even a plant with completely dead top growth may have a living rootstock that regenerates in spring. Do not remove apparently dead material until May when the extent of recovery is clear.

Corokia (wire-netting bush) is a distinctive New Zealand evergreen shrub with an interlaced, wiry divaricating branching habit, tiny spoon-shaped silver-backed leaves, yellow star flowers, and red or yellow berries. Hardy to about -10°C in freely draining conditions, it is popular in coastal UK gardens. Cold damage and drought stress cause leaf curl; the divaricating habit actually provides some inner-stem frost protection. Do not remove bare-stemmed winter plants until May.

Cold damage

Cold damage curls and drops the small leaves of corokia in hard UK winters; temperatures below about -10 to -12°C (or less in wet conditions) cause progressive leaf loss and can kill the stems. The plant may look entirely bare and dead in a hard winter; however, the wiry stems often protect inner buds within the divaricating framework, and the plant may recover and push new growth from March onwards even after apparently complete top-growth death. Scratch a stem to check for green living tissue before giving up on an apparently dead plant.

What to do

Choose a sheltered south or west-facing position; coasts and mild urban gardens are ideal. Ensure perfect drainage; lean, dry soil maximises cold tolerance significantly. Do not remove apparently dead material until May when new growth from surviving buds confirms what is alive. In colder UK areas, wrap young plants in fleece from November to March; established plants in sheltered positions are usually self-sufficient. Take semi-ripe cuttings in July to August as winter insurance.

Drought stress

Corokia is moderately drought-tolerant once established in well-drained soil; the small, spoon-shaped leaves curl inward along their length when the root zone dries out significantly in summer. Container-grown plants are most vulnerable, as the restricted root volume dries out quickly in warm weather. The silver-white felted undersides of the leaves are an adaptation to reduce water loss; the plant can roll its leaves to expose only the felted underside to the sun, reducing transpiration. This leaf-rolling in dry conditions is a normal adaptation and the leaves unfurl when conditions cool.

What to do

Water container-grown corokia regularly in summer; check every 1 to 2 days in warm weather. Established in-ground plants need watering only during prolonged dry spells. Mulch the root zone with bark to conserve moisture. The plants are well-suited to coastal gardens with freely draining, sandy soils where their drought tolerance is an advantage rather than a constraint.

Waterlogging

Corokia does not tolerate waterlogged or persistently wet soil; the roots rot in saturated conditions, causing leaves to yellow, curl, and drop and the plant to decline. The problem is most acute in heavy clay soils and in low-lying or poorly drained positions during wet UK winters. Freely draining soil is essential for reliable overwintering; good drainage is even more important than mild winter temperatures for long-term plant survival.

What to do

Plant in freely draining, well-aerated soil; add grit to clay soils. Raised beds and coastal garden conditions with freely draining, sandy or rocky soil are ideal. Do not over-irrigate in autumn or winter. A grit mulch around the base improves drainage at the root collar level in wet conditions.

Frequently asked questions

Why are my corokia leaves curling?

Corokia leaves curl most commonly because of cold damage in hard winters (leaves curl and drop below -10°C; the plant often recovers from the rootstock; do not remove until May), drought stress in summer (the small leaves curl along their length when dry; a normal drought-adaptation response; water and they recover), or waterlogging in wet soils (roots rot in saturated conditions; plant in freely draining soil). Cold combined with wet is the most damaging combination.

Is corokia hardy in the UK?

Corokia x virgata cultivars ('Bronze King', 'Red Wonder', 'Yellow Wonder') are hardy to about -10 to -12°C in freely draining, sheltered conditions and are reliable in most of southern and central England and Wales. Coastal gardens and sheltered urban positions suit them best. Corokia buddlejoides is less hardy (-5 to -8°C) and is restricted to mild UK gardens. In very cold areas, grow in containers and bring under glass from November to March.

How do I grow corokia in the UK?

Grow in full sun to light shade in well-drained, moderately fertile, neutral to slightly alkaline soil. Corokia is particularly well suited to UK coastal gardens: it tolerates salt wind, sandy soils, and mild maritime conditions that replicate its New Zealand open-country origins. Prune in spring (April to May) to control size; it responds well to clipping and can be used as an informal hedge. The yellow star flowers in spring are followed by ornamental red or yellow berries in autumn.

Why is my corokia losing its leaves?

Leaf drop in winter is often normal cold-stress behaviour rather than terminal decline; corokia may drop most of its leaves in hard winters but regrow from surviving buds in spring. Scratch a stem: green tissue beneath the bark means the stem is alive; brown tissue means it is dead. Check several stems at different heights before concluding the plant is dead. Do not remove apparently dead material until May when the extent of recovery is clear. Significant bark blackening, mushy stems, or root rot indicate more serious problems.