Plant problems

Why Are My Trachelospermum Leaves Curling?

Q: Why are my trachelospermum leaves curling?

Trachelospermum (star jasmine or confederate jasmine) leaves curl most commonly in the UK because of cold damage in winter, scale insect infestation on the stems and leaves, drought stress in containers or dry conditions, or waterlogging of the root zone. Trachelospermum jasminoides (star jasmine) is a self-clinging, evergreen, woody climber from East Asia with glossy, dark green, oval leaves and intensely fragrant white propeller-shaped flowers produced in July and August; it is grown in UK gardens as a wall climber for sheltered, warm positions in southern and western England, and is one of the most highly fragrant climbing plants available for UK gardens. Trachelospermum asiaticum (Japanese star jasmine) is a closely related, slightly hardier species with smaller, often less glossy leaves and smaller, more cream-coloured flowers. Both are marginally hardy in the UK: they need a sheltered, south or west-facing wall position to survive UK winters reliably. Cold damage is the most common winter problem: the glossy, evergreen leaves discolour, curl, and may be killed when temperatures fall below about -8 to -10°C, which can occur in cold UK winters or when the plant is in an exposed position. Scale insects, particularly soft scale (Coccus hesperidum) and brown soft scale, build up on the stems and leaf undersides of trachelospermum growing against warm, sheltered walls; infested leaves yellow and curl as the insects drain sap.

Q: Is trachelospermum hardy in the UK?

Trachelospermum jasminoides (star jasmine) is marginally hardy in UK outdoor conditions; its survival depends on the severity of the winter, the shelter of the planting position, and soil drainage. In ideal conditions (sheltered south or west-facing wall, well-drained soil, mild UK climate in southern or western England), Trachelospermum jasminoides can survive temperatures to about -8 to -10°C and is reliably evergreen and long-lived; in exposed positions, cold inland gardens, or on north or east-facing walls, the plant may be damaged or killed by UK winters. In practice, Trachelospermum jasminoides is best regarded as reliably hardy only in the mildest UK gardens (coastal and urban gardens in southern England, Wales, and western Ireland); in the rest of the UK it can be grown as a wall plant in sheltered positions but with the understanding that a particularly cold winter may damage or kill the top growth. Trachelospermum asiaticum (Japanese star jasmine) is considered slightly hardier than Trachelospermum jasminoides, surviving to about -12 to -15°C in ideal conditions; it is a better choice for less mild UK positions and is also effective as a ground-covering plant in sheltered positions. Both species need a warm, sunny wall position and well-drained soil; they do not tolerate waterlogging and will not survive in cold, wet, poorly draining soils. In cold UK areas (north of a line from Bristol to the Wash), both species are best considered conservatory or cool greenhouse climbers rather than reliable outdoor wall plants.

Q: How do I grow trachelospermum in the UK?

Trachelospermum jasminoides needs a sheltered, south or west-facing wall in full sun, well-drained fertile soil, and protection from cold north and east winds to thrive in UK outdoor conditions. The key requirements are: a warm wall (the thermal mass of a house or garden wall significantly raises the effective temperature around the plant in winter, which is critical for survival); full sun or at minimum 6 hours of direct sun daily (the flowers require warmth and light to open fully and produce their full fragrance; shaded plants flower poorly); well-drained but fertile soil (trachelospermum is not as drought-tolerant as Mediterranean plants and needs reasonable moisture alongside good drainage); and shelter from cold winds, particularly east and north-east winds that cause rapid moisture loss from the evergreen leaves in winter. Plant in spring after the last frost; train the young stems against the wall using wire or trellis supports as trachelospermum is a self-clinging climber that uses short stem roots (similar to ivy) but may need guidance in the early years before these develop fully. Mulch the root zone with composted bark in autumn to protect the roots and crown from hard frosts. In cold UK areas, bring container-grown plants into a frost-free conservatory or cool greenhouse for winter. Pruning: trachelospermum needs minimal pruning; trim in spring after flowering to shape and contain the plant, and remove any frost-damaged stems. The plant can be trained to cover a large wall surface over several years and is particularly attractive when the fragrant July to August flowers fill the evening air around a garden seating area or open window.

Q: Why has my star jasmine gone yellow?

Yellowing of trachelospermum leaves most commonly indicates cold damage in winter, scale insect infestation on the stems, waterlogging of the root zone, or magnesium deficiency. Cold damage causes the glossy, dark green leaves to yellow, then turn brown and curl, beginning at the leaf tips and margins; the damage is most visible in late winter (February to March) after a prolonged cold or frosty spell and is typically most severe on the most exposed parts of the plant. Scale insect infestation causes the leaves to yellow progressively as the insects drain sap; look for flat, brown or pale waxy bumps on the stems and leaf undersides, and for associated honeydew and sooty mould. Waterlogging causes yellowing and wilting that does not respond to watering; check the root zone for waterlogged or mushy roots. Magnesium deficiency (which can occur on plants grown in sandy, freely draining soils that have been leached of magnesium) causes interveinal yellowing of older leaves (the veins remain green while the tissue between them yellows); apply a foliar spray of Epsom salts (magnesium sulphate at 20 g per litre of water) to correct. Some degree of yellowing and leaf drop in late winter and early spring is normal for trachelospermum even in mild UK conditions; the plant undergoes a partial leaf renewal in early spring where older leaves yellow and drop before new growth begins. This spring yellowing affects the oldest leaves and is most pronounced after cold winters; it is normal and is not a cause for concern if the new growth that follows is healthy and dark green.

Trachelospermum jasminoides (star jasmine) is a glossy-leaved, self-clinging, evergreen East Asian climber grown in UK gardens for its intensely fragrant white flowers in July and August; one of the most powerfully scented climbing plants that can be grown outdoors in southern England. It needs a sheltered south or west-facing wall to survive UK winters reliably. Cold damage to the evergreen leaves and scale insects on sheltered wall plants are the most common causes of leaf curl.

Cold damage

Cold damage is the most common winter problem on trachelospermum in UK gardens. When temperatures fall below about -8 to -10°C, the glossy, dark green leaves discolour, yellow at the margins, curl inward, and in severe cases die and turn brown; the damage is most visible in late winter and early spring after a prolonged cold spell or hard frost. The extent of damage depends on the position: plants on a sheltered south-facing wall in a mild urban or coastal garden may show little or no damage in most UK winters, while plants in more exposed positions or cold inland gardens may lose most of their leaves in a harsh winter. In spring, some yellowing and leaf drop is normal even without frost, as the plant renews its oldest leaves before the new growing season begins.

What to do

Plant exclusively against a sheltered south or west-facing wall in well-drained soil; this single positioning decision determines how reliably the plant survives UK winters. Mulch the root zone with composted bark in late autumn (10 cm deep) to protect the roots and crown. Do not cut back cold-damaged leaves until April when new growth shows; the damaged leaves provide some protection to the stems and buds below. Once new growth is clearly extending, cut back all dead stems to healthy, budding tissue. In cold UK areas, grow in a container and bring inside for winter.

Scale insects

Scale insects, particularly soft scale (Coccus hesperidum) and brown soft scale, commonly build up on trachelospermum growing against warm, sheltered south-facing walls where the protected, warm microclimate allows scale populations to increase without the checks that cold, wet UK weather provides. Infested stems appear studded with flat, oval, brown or pale waxy scales; affected leaves yellow progressively and curl as the insects drain sap; heavy infestations produce honeydew that supports sooty mould growth on the leaves and stems. Scale on trachelospermum is most visible in spring and early summer when the crawlers (mobile juvenile stage) are present and populations are growing rapidly.

What to do

Apply insecticidal soap or horticultural oil spray to all stem surfaces and leaf undersides in late spring when the mobile crawler stage is most vulnerable; the spray must contact the scale insects directly. Repeat every 10 to 14 days for 3 to 4 treatments. Scrub established scale clusters from stems with a stiff brush dipped in insecticidal soap solution. Introduce Metaphycus helvolus (a parasitoid wasp) for biological control in conservatory or very sheltered wall conditions. Improve air circulation around the plant by thinning dense growth; the warm, sheltered wall environment that suits the plant is also ideal for scale.

Drought stress

Trachelospermum needs reasonable moisture alongside excellent drainage; it is not as drought-tolerant as Mediterranean wall plants (such as ceanothus or cistus) and in containers or in very freely draining soils, drought stress causes the glossy leaves to curl and develop brown margins. Container-grown trachelospermum is particularly vulnerable to drying out in summer; the restricted root volume in a pot dries out faster than the open ground. Newly planted wall specimens in the first season also need regular watering before establishing a deep enough root system to access moisture from a wider area.

What to do

Water container-grown plants regularly in summer; check the compost moisture every 2 to 3 days in hot weather and water when the top 5 cm is dry. Apply a mulch of composted bark around the base of wall-planted specimens to conserve moisture. Water newly planted wall specimens through the first summer. Ensure plants against south-facing walls (which can become very dry in summer) receive adequate moisture; wall-base soils tend to dry out faster than open-ground positions.

Waterlogging

Trachelospermum does not tolerate waterlogged or persistently wet soil; root rot develops in saturated conditions, causing progressive yellowing, wilting, and leaf curl that does not respond to watering. Waterlogging is most damaging in winter when root activity is lowest; the combination of wet soil and cold temperatures can kill the roots at temperatures well above the plant's frost threshold. In containers, waterlogging occurs when drainage holes are blocked or when pots sit in saucers of standing water.

What to do

Ensure good drainage at planting; add grit to heavy or compacted soils. The base of walls can sometimes be very wet because of water running off the wall surface; plant slightly away from the wall base (30 to 45 cm) where drainage is better. In containers, use free-draining compost and ensure drainage holes are clear; do not allow the pot to sit in standing water. Reduce watering to a minimum in winter; the plant needs very little water in cool, dormant conditions.

Frequently asked questions

Why are my trachelospermum leaves curling?

Trachelospermum leaves curl most commonly because of cold damage in winter (the evergreen leaves discolour, yellow at the margins, and curl when temperatures drop below -8 to -10°C), scale insects building up on stems and leaf undersides of sheltered wall-grown plants, drought stress in containers or dry wall-base soils in summer, or waterlogging causing root rot. Some normal leaf yellowing and curl in late winter as the plant renews its oldest leaves before spring is expected and not a cause for concern.

Is trachelospermum hardy in the UK?

Trachelospermum jasminoides is marginally hardy, surviving to about -8 to -10°C in ideal conditions against a sheltered south or west-facing wall in southern England. In exposed or cold inland positions it may be damaged or killed in harsh UK winters. Trachelospermum asiaticum is slightly hardier (to about -12 to -15°C). Both are best treated as fully reliable only in mild coastal and urban gardens in the south and west of the UK; in colder areas grow in containers brought inside for winter.

How do I grow trachelospermum in the UK?

Plant against a sheltered south or west-facing wall in full sun, in well-drained but fertile soil. Train against trellis or wires in the early years before the self-clinging stem roots develop. Mulch the root zone in autumn. Prune minimally in spring after flowering to shape and contain. Water adequately in summer (particularly wall-base soil and containers which dry out quickly). In cold UK areas, container grow and overwinter under glass.

Why has my star jasmine gone yellow?

Yellowing most commonly indicates cold damage (tips and margins yellow, then brown, after frost), scale insects (progressive yellowing with flat brown bumps on stems and leaf undersides), waterlogging (yellowing and wilting not responding to watering), or magnesium deficiency in sandy soils (interveinal yellowing of older leaves; treat with Epsom salts foliar spray). Some normal spring yellowing of the oldest leaves as the plant renews itself is expected even in healthy specimens.