Plant problems

Why Are My Leucothoe Leaves Curling?

Q: Why are my leucothoe leaves curling?

Leucothoe leaves curl most commonly in the UK because of wrong soil pH (too alkaline for this ericaceous plant), wind scorch, drought stress, or Phytophthora root rot. Leucothoe fontanesiana (drooping leucothoe or dog hobble) is an evergreen, ericaceous shrub from the moist woodlands of the eastern United States; it forms graceful, arching stems with glossy, lance-shaped leaves that often turn red, bronze, or purple in autumn and winter. Like all ericaceous plants (rhododendrons, camellias, pieris, blueberries), leucothoe requires acid soil with a pH below 6.0 and will develop lime-induced chlorosis (yellowing and curling of new growth) in alkaline or neutral soils. Wind scorch, particularly from cold east or north-east winds in winter, browns and curls the leaf margins and tips of the glossy, evergreen leaves; this is the most common visual problem on leucothoe growing in exposed positions in UK gardens and typically improves once the wind drops and new growth begins in spring. Drought stress causes the glossy leaves to curl inward and develop brown margins, particularly in the heat of summer in freely draining soils or in containers; leucothoe grows naturally in the cool, moist soil of stream banks and shaded woodland hollows and is sensitive to moisture stress. Phytophthora root rot, encouraged by poorly draining or compacted soil, causes root death, shoot wilting, and eventual plant collapse.

Q: Why are my leucothoe leaves turning red?

Leucothoe fontanesiana leaves naturally turn red, bronze, or deep purple in autumn and through winter, particularly when the plant is exposed to some direct sun or cooler temperatures; this is a completely normal and desirable characteristic of the plant, not a sign of a problem. The autumn and winter colour is one of the main ornamental reasons for growing leucothoe; varieties such as 'Rainbow' (also sold as 'Girard's Rainbow') have leaves that emerge green variegated with cream and pink and develop red or bronze tints in winter. 'Scarletta' is selected specifically for its intense, bright scarlet winter leaf colour. The winter colour fades as temperatures rise in spring and the plant produces new green growth. Some degree of red or bronze colouration can also occur in summer if the plant is exposed to strong direct sun; leucothoe prefers partial or dappled shade, and the leaves may develop yellow, orange, or red stress colouration if exposed to strong afternoon sun, particularly when the soil is dry. This sun stress colouration is less even and less attractive than the natural winter colour and is accompanied by curling of the leaf margins; it indicates that the plant would prefer more shade and more moisture. Overall, red or bronze leucothoe leaves in autumn and winter are entirely normal; unseasonal reddening in summer with curling margins indicates sun or drought stress.

Q: How do I grow leucothoe in the UK?

Leucothoe fontanesiana requires acid soil, consistently moist but well-drained conditions, and partial to full shade to thrive in UK gardens. The key requirements mirror those of rhododendrons and pieris: acid soil with a pH of 4.5 to 5.5; shelter from cold, desiccating east and north-east winds; consistent moisture without waterlogging; and a position in partial shade or dappled light (full sun causes leaf scorch, particularly in summer). The ideal position is under the light shade of deciduous trees in a peaty or leafy, humus-rich acid soil; the same conditions that suit azaleas and enkianthus will suit leucothoe. In areas with alkaline or neutral soil, leucothoe can be grown in containers of ericaceous compost watered with collected rainwater; it is also well-suited to raised acid beds where the soil can be managed and kept acidic. Leucothoe spreads by suckering to form a colony of arching stems; in a suitable position it makes a ground-covering mass of arching foliage that suppresses weeds and looks elegant throughout the year. The variegated form 'Rainbow' ('Girard's Rainbow') is particularly widely grown for its colourful foliage but is slightly less vigorous than the plain green-leaved form. Mulch annually with composted bark or leaf mould to maintain moisture and soil acidity. Leucothoe needs minimal pruning: remove old, tired, or crossing stems at the base in spring to maintain a fresh, well-furnished appearance.

Q: How do I prune leucothoe?

Leucothoe fontanesiana needs relatively little pruning; it produces its best arching form when not heavily cut back. The main pruning tasks are removing the oldest, most exhausted stems at the base to allow fresh young shoots to take their place; this is best done in early spring (February to March) before new growth begins. Cut the oldest stems (those that are clearly less vigorous and producing smaller leaves) to the ground; the plant produces new shoots from the base to replace them. Do not cut all stems back at once; remove only the oldest third each year on a rolling basis to maintain a continuous supply of young, fresh arching stems. Shorten any particularly long, straggly stems that have lost their graceful arching habit after flowering in spring. The small, white, tubular flowers are produced in hanging racemes in May; they are not the plant's main ornamental feature (the foliage is more important), but they should be allowed to finish before pruning. Do not cut leucothoe hard back into old, leafless wood; it does not regenerate reliably from old bare wood and such pruning can weaken the plant significantly. In cold winters, the tips of the arching stems may be killed by frost; these can be cut back to healthy, live tissue in spring when the extent of damage is clear.

Leucothoe fontanesiana (drooping leucothoe or dog hobble) is a graceful, evergreen ericaceous shrub from the shaded, moist woodlands of eastern North America, grown in UK acid gardens for its arching stems, glossy lance-shaped leaves, and beautiful red, bronze, or purple winter foliage. Like all ericaceous plants, it curls and yellows in alkaline soil; in UK conditions wind scorch on the glossy leaves and drought stress on the shallow root system are the most common additional causes of leaf curl.

Lime-induced chlorosis

Leucothoe fontanesiana is an ericaceous plant and cannot tolerate alkaline or neutral soil; in soil with a pH above 6.0, iron and manganese become unavailable to the plant and the new leaves yellow between the veins (interveinal chlorosis), curl, and develop brown margins. The problem worsens progressively if soil pH is not corrected; the plant fails to thrive and may eventually die in significantly alkaline soil. Watering with hard tap water in areas with chalky or limey water can also gradually raise the pH of container compost over time, causing lime-induced chlorosis to develop even in ericaceous compost.

What to do

Test soil pH before planting; leucothoe needs pH 4.5 to 5.5. Incorporate sulphur chips, composted pine bark, or acidic compost to lower the pH of slightly alkaline soils; retest after 8 to 12 weeks. In hard water areas or on alkaline soils, grow leucothoe in containers of ericaceous compost and water exclusively with collected rainwater. Apply chelated iron (sequestered iron) as an immediate treatment for chlorotic plants while soil conditions are being corrected. Avoid lime-containing fertilisers, mushroom compost, or hard tap water.

Wind scorch

The glossy, evergreen leaves of leucothoe lose moisture through their surface in cold, dry, windy conditions in winter even when temperatures are above freezing; the leaf tips and margins turn brown and curl inward as moisture loss exceeds the rate at which the roots can replace it. Wind scorch is most visible in February and March after a prolonged cold and windy spell, and is most common on plants in exposed positions or on those planted where east or north-east winds can reach them. The damage is cosmetic rather than life-threatening; the plant typically recovers in spring as new growth replaces the scorched leaves.

What to do

Plant leucothoe in a sheltered position with protection from cold east and north-east winds; the shelter of trees, a fence, or a wall on the east side is the most effective long-term solution. Do not prune wind-scorched shoots until new growth is visible in spring; then cut back any dead or badly damaged stem tips to healthy tissue. In particularly exposed gardens or in the first winter after planting, protect with windbreak netting on the exposed side.

Drought stress

Leucothoe grows naturally in the consistently moist, humus-rich soil of stream banks and shaded woodland hollows in eastern North America; it is not drought-tolerant and will curl the leaf margins, drop leaves, and may wilt when the root zone dries out. Drought stress is most likely in containers, in freely draining sandy soils, in positions in full sun where evaporation is greatest, and during extended dry spells in summer. The shallow, fibrous root system typical of ericaceous plants is particularly sensitive to drying at the surface.

What to do

Maintain a deep mulch (5 to 10 cm) of composted bark, leaf mould, or pine needles around the plant at all times; mulching is the most effective way to retain the consistent moisture leucothoe needs. Avoid positions in full sun or in dry, freely draining soils. Water container-grown specimens regularly in summer, using rainwater; allow the compost surface to begin drying before watering but never allow the root ball to dry out completely. Plant in dappled or partial shade rather than full sun to reduce moisture demand.

Phytophthora root rot

Phytophthora species (water moulds) can infect leucothoe through waterlogged or poorly draining soil; root rot develops rapidly in anaerobic, saturated conditions, causing the roots to turn brown and mushy. The above-ground symptoms are progressive wilting, leaf curl, yellowing, and eventual shoot and plant collapse; the symptoms may appear suddenly in summer when a waterlogged root system fails to supply the plant during hot weather. Phytophthora is most damaging on leucothoe planted in heavy clay soils or in low-lying, poorly draining positions.

What to do

Ensure excellent drainage at planting; incorporate substantial grit or coarse gravel into heavy clay soils, or choose a naturally well-draining, sloping position. Avoid waterlogging at all times, particularly in winter; leucothoe needs consistently moist but aerated soil, not saturated soil. If root rot is confirmed (roots brown and mushy on inspection), remove the plant, trim dead roots to healthy tissue, replant in improved drainage conditions, and water very sparingly until new growth is established. There is no effective chemical treatment for established Phytophthora infection.

Frequently asked questions

Why are my leucothoe leaves curling?

Leucothoe leaves curl most commonly because of wrong soil pH (alkaline or neutral soil causes lime-induced interveinal chlorosis and curling margins), wind scorch (cold east winds in winter brown and curl the leaf tips and margins of the glossy evergreen leaves), drought stress (the shallow root system and thin leaves are sensitive to drying out), or Phytophthora root rot in waterlogged conditions. Leucothoe is very trouble-free in the right acid, moist, sheltered woodland conditions; most problems trace back to unsuitable soil pH, poor drainage, or an exposed, dry position.

Why are my leucothoe leaves turning red?

Leucothoe fontanesiana naturally turns red, bronze, or purple in autumn and winter; this is entirely normal and desirable. 'Scarletta' is selected for intense scarlet winter colour; 'Rainbow' has variegated green, cream, and pink leaves that deepen in winter. The colour fades as temperatures rise in spring. Reddening or bronze colouration in summer with curling margins indicates sun or drought stress; the plant needs more shade and more moisture.

How do I grow leucothoe in the UK?

Grow in acid soil (pH 4.5 to 5.5), in partial to full shade, in consistently moist but well-drained humus-rich soil; maintain a deep bark or leaf mould mulch. In alkaline or hard water areas, grow in containers of ericaceous compost watered with rainwater. The conditions needed match those for rhododendrons and pieris. The arching stems look best when unpruned; remove only the oldest stems at the base each spring.

How do I prune leucothoe?

Prune minimally in early spring: remove the oldest, least vigorous stems at the base each year on a rolling basis (oldest third each spring) to encourage fresh new arching growth. Shorten over-long stems after flowering in spring. Do not cut into bare old wood; leucothoe does not regenerate reliably from leafless stems. Cut frost-damaged tips back to healthy tissue in spring once new growth confirms the extent of damage.