Nothofagus Leaves Curling and Browning
Drought stress and late frost are the most common reasons nothofagus leaves curl and brown. This guide shows you how to identify each cause and keep southern beech growing vigorously toward its graceful canopy.
1. Drought stress
Drought stress is the most common cause of leaf curl and browning in nothofagus during establishment and in hot, dry summers. The naturally moist, cool conditions of southern South America and New Zealand, where most nothofagus species originate, give them a genuine requirement for consistent soil moisture that can be difficult to satisfy in the drier parts of the UK. Young trees in their first three years after planting and trees on free-draining soils are most susceptible.
What to look for
The small, often crinkled or toothed leaves curl and droop during the hottest part of the day, with the margins rolling toward the underside. In the deciduous species, the leaf margins turn brown and papery in prolonged drought. Nothofagus antarctica shows particularly dramatic leaf curl and marginal browning in dry conditions due to its small, crinkled leaves and the large surface area they present relative to their mass. The soil beneath the tree is very dry at depth. Recovery overnight after mild drought may partially reverse the curling, but prolonged drought results in premature leaf fall on deciduous species.
What to do
Water young nothofagus deeply at least once a week during any dry spell in their first three growing seasons. Apply a generous mulch of leaf mould or bark chip 100 mm deep across the root zone to conserve moisture and replicate the leaf litter conditions of the tree's natural forest habitat. A north or east-facing position, or one receiving some afternoon shade, suits nothofagus in drier UK gardens better than an exposed south-facing aspect. Once established, nothofagus obliqua and nervosa are vigorous trees with deep root systems that can access moisture from a wide area; drought rarely threatens established specimens except in the driest east of England conditions.
2. Late frost damage
Nothofagus leafs out early in spring, with deciduous species expanding their new leaves from March or April, and the soft emerging foliage is vulnerable to late frosts. Nothofagus nervosa in particular is known to leaf out early and be prone to late frost damage in exposed or frost-prone positions. The tree recovers readily from late frost damage, producing new growth from secondary buds within two to three weeks, but repeated late frost events over several seasons can affect tree vigour and form.
What to look for
The current season's expanding leaves turn black or dark brown suddenly following a late frost in April or May. The damage is most severe on the youngest, most recently emerged growth at the shoot tips, while older, partially hardened leaves on the same branch may show only marginal browning. The affected leaves hang limply from the shoot before drying to a papery brown. New growth emerges from surviving buds within two to three weeks in most cases. In a frost pocket or exposed position, successive frosts over several springs can produce a characteristic stunted, multi-budded growth pattern at shoot tips as the tree repeatedly breaks secondary and tertiary buds.
What to do
Plant nothofagus in a position with good cold-air drainage, avoiding frost pockets at the base of slopes or in enclosed hollows. A sheltered position with some protection from late frost, such as a west-facing wall or the canopy of established shelter trees, significantly reduces frost risk. Avoid pruning frost-damaged growth until new shoots are clearly visible below the damaged portions. For young trees in particularly frost-prone gardens, a light covering of horticultural fleece on forecast frost nights in April and May gives effective protection. The tree's natural recovery from frost damage is rapid and typically complete within the same growing season.
3. Phytophthora root rot
Nothofagus is susceptible to Phytophthora root rot, particularly on poorly draining sites or in wet winters. The disease causes progressive root death that leads to foliage yellowing and browning beginning at the base of the canopy and spreading upward. The evergreen nothofagus species are somewhat more susceptible than the deciduous species in wet conditions. The problem is most common in heavy clay soils or in gardens with impeded drainage.
What to look for
Foliage transitions from normal green to pale green, then yellow, then brown, in a pattern that begins in the lower canopy and spreads progressively upward. The browning does not respond to watering. Scraping the bark at the base of the trunk reveals dark, reddish-brown discolouration beneath the bark rather than healthy green or cream tissue. The roots, if examined, are dark and rotten rather than pale and firm. Unlike drought or frost damage, which produce clearly defined patterns of leaf curl or tip browning, Phytophthora decline is a gradual, progressive worsening of the whole tree's appearance over one to several seasons.
What to do
There is no effective chemical treatment once Phytophthora is established. Remove affected trees and replace as much surrounding soil as possible. Substantially improve drainage before replanting. Do not replant susceptible nothofagus species in a position where Phytophthora has been confirmed. The best prevention is choosing a well-drained planting position from the outset; nothofagus requires moist but never waterlogged soil, and the distinction between adequate moisture and waterlogging is critical to long-term health. An established Phytophthora outbreak is effectively impossible to eradicate from the soil.
4. Wind scorch
The leaves of nothofagus, particularly the small, crinkled leaves of Nothofagus antarctica, are susceptible to desiccation from persistent cold or drying winds. Young trees in exposed positions can suffer significant wind scorch in late winter and early spring, when cold easterly airflow coincides with the early leaf emergence of deciduous species or with the period when evergreen species have least capacity to replace lost moisture. Wind scorch is most damaging in the first two winters after planting, before the root system is fully established.
What to look for
Leaf margins turn brown and dry on the windward side of the canopy. The browning is concentrated on the outermost and most exposed leaves, while the sheltered inner canopy remains green. In deciduous species, the already-expanded leaves of spring are most affected; in evergreen species, the outer leaves of the canopy facing the prevailing cold wind develop the characteristic bleached, papery browning. Salt-laden coastal winds produce similar directional browning. The directional pattern and its correlation with the wind source is the key diagnostic feature.
What to do
Plant nothofagus in a position sheltered from prevailing cold and drying winds. A semi-sheltered position suits the naturally forest-edge habit of most species better than fully exposed conditions. A permeable windbreak of established hedging or mesh to windward of a young tree provides effective protection in the first few years of establishment. Wind-scorched leaves are cosmetic damage that is covered by new growth through the growing season. Maintaining consistent soil moisture reduces wind scorch severity by ensuring the tree has adequate water reserves to replace what is lost through desiccated foliage.
5. Alkaline soil chlorosis
Nothofagus originates from naturally acidic to neutral soils in South America and New Zealand and performs poorly on chalk or strongly alkaline soils. In alkaline conditions, iron and manganese become locked into forms unavailable to the roots, causing a characteristic deficiency chlorosis in which the leaf tissue between the veins yellows while the veins themselves remain green. The young growth at the shoot tips is typically most severely affected, producing the diagnostic interveinal yellowing pattern on emerging leaves.
What to look for
Young leaves emerge pale yellow or lime-green rather than the normal healthy green. The tissue between the leaf veins yellows while the veins themselves remain distinctly greener, producing the characteristic interveinal pattern of iron deficiency. The problem is most severe on the current season's growth at the shoot tips. Older, already-hardened leaves may be less affected, as they stored nutrients before the deficiency became limiting. Soil pH testing confirms alkaline conditions above pH 7. The problem worsens over successive seasons as the tree fails to extract adequate iron from the soil.
What to do
Correct soil pH before planting where possible by incorporating sulphur chips or acidifying organic matter such as composted pine bark. In existing plantings, apply a sequestered iron chelate in spring to make iron available despite alkaline conditions; repeat in midsummer. Mulching generously with pine bark or leaf mould gradually acidifies the soil surface over several years. In strongly chalk or limestone soils, nothofagus is genuinely difficult to grow well and an alternative tree with better chalk tolerance is a more practical choice for the long term.
Frequently asked questions
Does nothofagus lose its leaves in winter?
It depends on the species. Nothofagus obliqua (roble beech) and Nothofagus nervosa (rauli) are deciduous, losing their leaves in autumn with good autumn colour before the winter. Nothofagus antarctica (antarctic beech) is also deciduous but has charming small, crinkled leaves with attractive autumn colour. Nothofagus betuloides and Nothofagus dombeyi are evergreen species from wetter parts of South America and retain their foliage year-round. Both evergreen species are slightly less hardy than the deciduous species and better suited to milder areas of the UK.
Is nothofagus hardy in the UK?
The commonly grown deciduous nothofagus species, particularly Nothofagus obliqua and Nothofagus nervosa, are fully hardy throughout the UK and grow exceptionally vigorously in the mild, moist conditions of the west and north. Nothofagus antarctica is also fully hardy. The evergreen species, particularly Nothofagus betuloides and Nothofagus dombeyi, are hardier than many evergreen trees but can suffer significant damage in very cold inland winters; they are best suited to the west of England, Wales, Scotland, and Ireland where maritime conditions moderate winter temperatures.
How fast does nothofagus grow?
Nothofagus obliqua (roble beech) is among the fastest-growing broadleaved trees available for UK gardens, capable of adding 60 to 90 cm per year in good conditions. It can reach 15 to 20 metres in twenty years in a suitable moist, sheltered position. Nothofagus nervosa (rauli) is similarly vigorous. This exceptional rate of growth makes deciduous nothofagus a remarkable choice for quickly creating shelter or screening in large gardens. Nothofagus antarctica is considerably slower, while the evergreen species are intermediate in growth rate.
Why are my nothofagus leaves so small this year?
Unusually small leaves on nothofagus typically indicate stress of some kind during the previous season or during the current season's leaf expansion period. Drought stress in the previous summer can reduce the resources available for the following season's growth. Late frost damage to the expanding leaves causes them to restart from secondary buds, which often produce smaller leaves than normal. Root disturbance from nearby construction or digging damages the root system and reduces the tree's ability to support full-sized foliage. In most cases, restoring good growing conditions produces normal-sized leaves in the following season.
What soil does nothofagus prefer?
Nothofagus performs best in moist, free-draining, slightly acidic to neutral soil with good organic matter content. It dislikes chalk or strongly alkaline soils, which cause iron deficiency chlorosis. The deciduous species, particularly Nothofagus obliqua and Nothofagus nervosa, are more tolerant of a range of soil conditions than the evergreen species, and both do well in the moisture-retentive but well-drained acid soils common in the north and west of the UK. Waterlogging causes root damage and progressive decline in all species. The tree is sensitive to root disturbance and transplants best when young.
Find the best spot for your plants
Plant Compass maps the sun path across your windows so you know exactly which plants will thrive in each spot before you buy. Coming soon to the App Store.
Learn more