Pittosporum Leaves Curling

Wind scorch and cold damage

Wind scorch and cold damage are the most common cause of leaf curling on pittosporum in UK gardens. Pittosporum tenuifolium, the most widely grown species, is a native of New Zealand and is classified as semi-hardy in the UK, thriving reliably in mild coastal and southern gardens but suffering in colder inland sites or in any exposed, wind-swept position. The damage occurs when cold, drying winds draw moisture out of the leathery evergreen leaves faster than the roots can replace it, causing the leaf margins and tips to turn brown and curl inward. Whole leaves may curl tightly and eventually drop. The damage is most severe in winter and early spring, particularly after periods of hard frost followed by cold, dry easterly winds. Purple-leaved and variegated forms of pittosporum tend to be slightly less hardy than the straight green-leaved species. The fact that pittosporum retains its leaves year-round means all its foliage is exposed to winter conditions, unlike deciduous shrubs that shed their leaves before the harshest weather arrives.

Plant pittosporum in a sheltered position, ideally against a south or west-facing wall or fence, or in the lee of a hedge or larger building. In colder gardens, choose hardier named varieties. Provide a windbreak on the exposed side with temporary horticultural fleece in hard winters. Do not cut back wind-scorched growth until spring, when the extent of the damage is clear and new growth has begun, as the scorched stems provide some protection to the live tissue behind them. Once new growth begins in spring, cut back to healthy tissue. Feeding with a general balanced fertiliser in spring encourages vigorous recovery growth.

Scale insects

Scale insects are a common pest on pittosporum and one of the most frequent reasons the plant looks unhealthy despite being in a reasonable position. The brown soft scale (Coccus hesperidum) and other scale species colonise the stems and the undersides of the leathery leaves, feeding on the sap. Above the insects, the leaves yellow and eventually curl as the infestation weakens the plant. The insects secrete honeydew, which drips onto the leaves below the infestation and creates ideal conditions for sooty mould to develop, turning the stems and older leaves black. The combination of yellowing on some leaves and sooty mould on others can make scale damage difficult to diagnose at first glance. Looking closely at the stems, particularly in the joint between a leaf stalk and the stem, reveals the flat, waxy, brownish limpet-like scales attached firmly to the surface. Heavy infestations on an otherwise healthy pittosporum are surprisingly common because the dense, evergreen growth of the plant provides ideal shelter for scale colonies to develop unnoticed.

Light scale infestations on pittosporum can be controlled by wiping the insects off the stems with a damp cloth soaked in soapy water, or by scrubbing with a soft brush. For heavier infestations, apply horticultural oil spray to all stems and leaf undersides in late spring when the young crawlers are active and most vulnerable. A second application six weeks later improves control. Cutting out the most heavily colonised old stems during the annual spring tidy reduces the population significantly. Washing the sooty mould off the leaves with soapy water after treating the scale improves the plant's photosynthetic capacity during recovery.

Drought

Drought stress causes pittosporum leaves to curl inward as the plant reduces its exposed leaf surface to conserve moisture. Although pittosporum's leathery leaves are moderately tolerant of dry conditions once the plant is established, young plants in their first one to two seasons in the ground are susceptible in prolonged dry summers. Plants in containers are the most drought-vulnerable because the restricted root volume dries out rapidly in warm weather. Wall-trained pittosporum is also more drought-prone than open-grown plants because the wall absorbs heat and rainfall reaches the soil at the plant's base only obliquely. In early stages of drought stress, the curling is reversible and the plant recovers quickly once watered; prolonged drought causes permanent browning at the leaf tips and margins.

Water newly planted pittosporum consistently through its first two summers. Apply a thick mulch of bark or garden compost annually, keeping it away from the main stems, to retain soil moisture around the root zone. Container pittosporum needs regular watering throughout the growing season. Established garden plants are generally self-sufficient in typical UK summers but may benefit from supplementary watering during extended dry spells, particularly those trained against walls or in very free-draining soils.

Aphids

Aphids colonise pittosporum in spring, targeting the soft new growth at the shoot tips. Dense colonies of pale green or yellowish aphids cluster at the tips and cause the youngest leaves to curl around the insects. Infestations on pittosporum are usually less severe than on many other shrubs because the relatively tough, leathery texture of even the youngest pittosporum leaves limits the damage compared with softer-leaved plants. Natural predators, particularly aphid parasitic wasps and ladybirds, usually arrive in sufficient numbers to control the infestation without intervention on established plants. A heavy infestation in spring on a young, newly planted pittosporum is more damaging than the same level of infestation on a mature shrub.

Treat aphid colonies on pittosporum with a strong jet of water directed at the shoot tips to dislodge the insects. Insecticidal soap spray provides chemical control if natural predators are slow to arrive. The relatively tough foliage of pittosporum makes it resilient to moderate aphid pressure, and well-established plants rarely require treatment. Avoid broad-spectrum systemic insecticides that would harm the beneficial insects that naturally regulate aphid populations on and around pittosporum.

Waterlogging

Waterlogging causes root rot in pittosporum and produces symptoms of yellowing leaves, leaf curl, and general decline. Plants in heavy clay soil or in low-lying positions where water collects after rain are most at risk. The damage from waterlogging is often gradual, with the plant slowly declining over one or more growing seasons as the root system is incrementally damaged. By the time the above-ground symptoms are severe, root damage is usually extensive. Pittosporum planted in containers is also susceptible if the pots lack adequate drainage holes or if the plants are left standing in water.

Plant pittosporum in well-drained soil. In heavy clay, incorporate grit and organic matter and create a slightly raised planting position. Container pittosporum must be in free-draining compost with generous drainage holes. If a plant has been waterlogged but is still showing some healthy growth, lift it, remove any rotted root tissue, and replant in a drier position with improved drainage. Waterlogging combined with cold winter conditions is particularly damaging, as both stresses simultaneously affect root function and the plant cannot recover until conditions improve.

Vine weevil

Vine weevil grubs feed on pittosporum roots over winter, and the above-ground symptoms appear in spring as unexplained wilting, curling leaves, and dieback that does not respond to watering. The adults notch the leaf margins with characteristic semicircular cuts in summer and autumn, which is the most recognisable above-ground sign of vine weevil activity. Container pittosporum is particularly vulnerable because the grubs can systematically work through the root ball in a restricted soil volume. Open-ground pittosporum is less often severely affected because the root system extends into a larger soil volume and the plant can tolerate greater root loss before showing above-ground symptoms.

Inspect container pittosporum roots in autumn by removing the plant from its pot and checking for cream-coloured, C-shaped grubs in the compost. Apply pathogenic nematode controls (Heterorhabditis bacteriophora) in late summer when soil temperatures are above 10 degrees Celsius, keeping the compost moist for at least two weeks. Repot into fresh compost after treatment. Sticky barriers around container rims prevent adult weevils climbing in to lay eggs. In the open garden, maintaining generally good soil health and avoiding the persistent moisture in the root zone that vine weevils prefer for egg-laying reduces the risk.

Frequently asked questions

Why are my pittosporum leaves curling?

Cold wind and frost damage is the most common reason pittosporum leaves curl and scorch, as the plant is semi-hardy and vulnerable to harsh winter conditions. Scale insects cause yellowing and curling by feeding on the sap on the stems and leaf undersides. Drought stress causes the leathery leaves to curl inward in hot, dry summers.

Is pittosporum frost hardy?

Pittosporum tenuifolium and most commonly grown varieties are semi-hardy and will tolerate light frosts, but they suffer significant leaf damage and curling in prolonged cold below minus 5 degrees Celsius or in exposure to cold, drying winds. They perform best in mild, sheltered gardens in the south and west of the UK. In colder or more exposed gardens, choosing the hardier varieties and providing a sheltered position against a south or west-facing wall greatly improves survival.

Why are pittosporum leaves turning brown and curling at the edges?

Brown, curled leaf margins on pittosporum most often indicate wind scorch or cold damage, where the exposed leaf edges are desiccated by cold or drying winds faster than the roots can replace moisture. This is most severe on exposed, windy sites in winter and early spring. Scale insect infestations can also cause marginal browning and curling as the plant becomes weakened. Drought stress produces similar browning on the leaf tips and margins in summer.

What is eating my pittosporum leaves?

The most likely culprits eating pittosporum foliage are vine weevil adults, which notch the leaf margins with semicircular cuts in summer and autumn, and caterpillars of various moth species. Scale insects suck sap rather than eating leaf tissue and are identified by the waxy brown or grey limpet-like bumps on the stems. Aphids occasionally colonise the new growth in spring, causing curling but not obvious holes.