Cryptomeria Leaves Curling and Browning
Drought stress and Cryptomeria blight are the most common reasons cryptomeria foliage turns brown and curls. This guide shows you how to identify each cause and keep Japanese cedar looking its best through every season.
1. Drought stress
Drought stress is the most common cause of foliage browning in cryptomeria, particularly in container-grown specimens and in young plants in their first few years after planting. Cryptomeria japonica grows naturally in the moist, humid mountain forests of Japan and China, where rainfall is high and soil moisture consistent. In UK gardens, particularly on free-draining soils or during dry summers, the tree struggles when its moisture requirements are not met, and the effect on its fine, soft foliage is rapid and distinctive.
What to look for
Shoot tips turn brown and the needle-like foliage at the extremities of the branches becomes dry, curled, and papery. The browning has a warm tan or rust colour rather than the darker brown of fungal blight. In a recently planted tree, entire shoot systems may brown and die back from the tips inward. On container plants, the root ball may have pulled away from the sides of the pot, indicating it has dried out thoroughly. The problem is worst on the most exposed outer foliage and in positions receiving strong sun or drying winds.
What to do
Water young cryptomeria deeply at least once a week during any dry spell throughout their first two growing seasons. For container specimens, check moisture levels every two to three days in summer and water as soon as the top few centimetres of compost feel dry. Apply a generous mulch of bark chip or well-rotted compost 100 mm deep across the root zone of ground-planted specimens to conserve moisture. If a container root ball has dried out completely and is difficult to rewet, stand the container in a bucket of water for several hours to allow the root ball to rehydrate slowly from the base. Prune out dead browned shoot tips after watering and recovery, as new growth will not regenerate on dead tissue.
2. Cryptomeria blight
Cryptomeria blight, caused primarily by the fungal pathogen Pestalotiopsis funerea and related species, is a significant disease of cryptomeria in the UK, causing progressive browning that moves from the inner foliage outward through the plant. It is most severe in warm, humid conditions with poor air circulation and is often associated with plants already weakened by drought, waterlogging, or other stress factors.
What to look for
Browning begins in the interior of the plant, typically around the oldest foliage closest to the trunk and main branches, and spreads outward to the shoot tips. This inside-out pattern of browning distinguishes blight from drought, which starts at the outer shoot tips. Affected foliage turns grey-brown or dark brown and remains attached to the plant rather than dropping cleanly. In wet conditions, small, dark fruiting bodies of the fungus may be visible on affected tissue with a hand lens. Branches within the browned zone may die back completely as the disease progresses.
What to do
Improve air circulation around the plant by removing overcrowding vegetation nearby. Prune out affected material, cutting back to healthy green tissue and sterilising cutting tools between cuts with methylated spirits. Bin all removed material. Avoid wetting the foliage when watering; water at the base of the plant and do so in the morning so any accidental foliage wetting dries during the day. A copper-based fungicide applied preventively in spring and again in autumn can reduce the risk of new infections. Keep the tree in good health through appropriate watering and mulching, as stressed trees are far more susceptible.
3. Spider mites
Spider mites, particularly the spruce spider mite (Oligonychus ununguis), commonly attack cryptomeria during hot, dry summers. They feed on the fine needle-like foliage, draining cell contents and producing a characteristic bronzing and stippling before the foliage browns and curls. Spider mite damage is most severe in July and August and is consistently worse on plants already under drought stress.
What to look for
Foliage develops a dusty, bronze, or stippled pale appearance, losing its normal rich green tone. The shoot tips may curl slightly as tissue is damaged. In heavy infestations, very fine silky webbing is visible on the foliage, particularly in the junctions between branchlets. Tap an affected shoot over white paper; the mites fall onto the paper as slow-moving specks, confirming their presence. The damage typically begins on the lower, older foliage and works upward and outward through the season.
What to do
Maintain consistent soil moisture, as water-stressed cryptomeria is significantly more susceptible to spider mite attack. Misting the foliage with plain water in the morning during hot, dry spells reduces mite populations by increasing humidity. For established infestations, spray all foliage surfaces thoroughly with horticultural soap solution or a plant-oil-based miticide, repeating every five to seven days for three applications. Encourage natural predatory mites by avoiding broad-spectrum pesticides. A preventive plant-oil spray in late June can reduce the severity of summer infestations in gardens where mites are a recurring problem.
4. Phytophthora root rot
Phytophthora root rot, caused by water moulds including Phytophthora cinnamomi, is a serious disease of cryptomeria on poorly draining soils. The pathogen attacks the root system, causing progressive root death that manifests as wilting, browning, and eventual death of the plant above ground. There is no effective chemical treatment, making prevention through appropriate site preparation essential.
What to look for
The plant declines progressively regardless of watering. Foliage turns grey-green and then brown, typically from the base of the plant upward, and the browning does not respond to improved irrigation. Scraping the bark at the base of the trunk reveals dark reddish-brown tissue beneath rather than the healthy cream or green of a live plant. The roots, when exposed, are dark and rotten rather than pale and firm. The problem is most common on heavy clay soils or where water collects after rain.
What to do
Prevent Phytophthora by ensuring excellent drainage before planting: incorporate coarse grit into clay soils, avoid low-lying positions, and do not overwater. There is no effective chemical cure for an established infection. Affected plants should be removed, including as much root material as possible. Replace the soil in that area with fresh material before replanting, and do not replant the same or related species in the same position. Adjacent healthy plants can be treated preventively with a phosphonate-based product, which reduces susceptibility without curing active infection.
5. Wind and frost scorch
Cryptomeria foliage is susceptible to desiccation from strong, cold winds, particularly in exposed positions in winter. Cold, drying winds cause the fine foliage to lose moisture faster than the roots can replenish it through cold, near-frozen soil, causing browning on the windward side of the plant. This is distinct from the natural winter bronzing of many cultivars and involves actual tissue death.
What to look for
Browning is concentrated on one side of the plant: the side facing the prevailing cold wind or the most exposed aspect. The browning is sharp and directional rather than progressive from inside out. The damaged foliage has a bleached, dead quality and does not recover in spring as natural winter bronzing does. In severe cases of cold wind desiccation, entire branches on the windward side can brown and die while the sheltered side of the plant remains green.
What to do
Plant cryptomeria in a position sheltered from the prevailing cold winter wind, ideally with the protection of other established trees or a building to the north and east. In an exposed garden, erect a temporary windbreak of permeable mesh around young plants during their first two or three winters. On established plants, a light spray of anti-desiccant product (such as wilt-pruf) on the foliage in November provides some protection by reducing moisture loss from the leaf surface in cold, dry winter winds. Water the root zone in autumn before the ground freezes to ensure the plant goes into winter with adequate moisture reserves.
Frequently asked questions
Is it normal for cryptomeria to go brown in winter?
Yes. Many cryptomeria cultivars naturally develop a bronze, reddish-brown, or purple-brown winter colouration in response to cold temperatures. The most strongly bronzing cultivars include 'Elegans' and 'Elegans Compacta', which turn vivid reddish-purple in winter. This is a natural physiological response and not a sign of disease or cold damage. The foliage returns to its normal green tone in spring as temperatures rise. The degree of bronzing varies with the cultivar and the severity of the winter.
Why has my cryptomeria gone completely brown?
Complete browning of cryptomeria across the whole plant is a serious symptom, most commonly caused by Cryptomeria blight (Pestalotiopsis), severe drought, Phytophthora root rot, or very cold, desiccating winter winds. The cause can usually be distinguished by the pattern and timing of browning: blight shows as progressive browning from the inner foliage outward; drought browning affects the shoot tips first; Phytophthora causes browning from the base up; wind scorch is concentrated on the windward side. If the browning is total and no green tissue remains, the plant has likely died.
How often should I water a cryptomeria in a container?
Container cryptomeria needs watering when the top 3 to 5 cm of compost feel dry. In summer during warm weather this may be every two to three days; in cool, wet conditions every week or two. The greatest risk for container conifers is allowing the root ball to dry out completely in summer; once a peat or bark-based compost dries out thoroughly it becomes hydrophobic and very difficult to rewet evenly. Regular checking and consistent watering during the growing season prevents this problem.
Does cryptomeria need acidic soil?
Cryptomeria japonica performs best in neutral to slightly acidic soil with a pH between 5.5 and 6.5. It tolerates neutral soils well but does not thrive on strongly alkaline chalk soils, where it may develop chlorosis and grow poorly. Moist, humus-rich, well-drained soil in a reasonably sheltered position suits it best. It does not tolerate permanently waterlogged conditions, despite its need for consistent moisture.
How big does cryptomeria get?
The species Cryptomeria japonica eventually reaches 20 to 30 metres but takes many decades to approach these dimensions in UK conditions. Most garden cultivars are considerably smaller: compact varieties such as 'Globosa Nana' stay below 1.5 metres; 'Elegans Compacta' reaches 2 to 3 metres; the larger cultivar 'Elegans' may eventually reach 8 to 10 metres. The very large species form is rarely planted in garden settings; choose a cultivar appropriate to the space available.
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