Plant problems

Why Are My Embothrium Leaves Curling?

Q: Why are my embothrium leaves curling?

Embothrium coccineum (Chilean fire bush or Chilean flame tree) leaves curl and yellow most commonly in UK gardens because of alkaline or chalky soil (embothrium requires acid, humus-rich soil and turns chlorotic, with yellowing leaves that curl at the margins, in neutral to alkaline conditions), drought stress (the long, narrow leaves curl inward when the root zone dries out), or cold damage in hard winters (embothrium is marginally hardy and the leaves and tips of young growth are damaged by hard frost). Embothrium coccineum is one of the most spectacular flowering trees or large shrubs that can be grown in UK gardens; in late May to June, established plants in mild, sheltered gardens produce an extraordinary display of hundreds or thousands of brilliant scarlet-orange, tubular flowers that cover the long, arching branches in dense clusters, creating a fiery, incandescent effect that is unlike any other UK-hardy plant. It is native to southern Chile and Patagonia, where it grows in cool, moist, acid, peaty soils in high rainfall areas, often in partial shade at the forest edge; this gives a clear indication of the conditions it needs in UK gardens. The most commonly grown form in UK gardens is Embothrium coccineum var. lanceolatum, particularly the cultivar 'Norquinco Valley', which is the hardiest and most widely available form; it can be a semi-evergreen large shrub or small tree reaching 4 to 8 m in sheltered UK conditions. Embothrium grows best in the wettest, mildest areas of the UK (western Scotland, Ireland, Wales, Cornwall, Devon) where the combination of mild winters, high rainfall, acid soils, and high humidity most closely replicate its native conditions.

Q: Is embothrium hardy in the UK?

Embothrium coccineum is marginally hardy in the UK; the form most commonly grown, 'Norquinco Valley' (also sold as E. coccineum var. lanceolatum 'Norquinco Valley'), is the hardiest and is reported to survive temperatures to about -10 to -15°C in ideal conditions. The plant is reliably perennial and has reached impressive sizes in sheltered gardens throughout mild, wet parts of the UK (western Scotland, where it is particularly spectacular at gardens such as Crarae, Benmore, Inverewe, and Logan; western Ireland; Wales; Cornwall and Devon). In drier, colder parts of the UK (the east and north of England, exposed inland positions), embothrium is much less reliable and may be damaged or killed in hard winters or by late spring frosts that damage the early-emerging growth. The combination of cold and dry is most damaging; embothrium in the warm, moist west of the UK encounters much less winter cold stress than might be implied by the temperature figures alone. Cold wind is particularly damaging to the large, leathery leaves; a sheltered position is essential outside the mildest parts of the UK. The leaves of the 'Norquinco Valley' form are narrower and less leathery than those of the typical species, and the plant is semi-evergreen to deciduous in colder UK winters, regrowing from the rootstock in spring; in mild western UK gardens it is largely evergreen and builds up a substantial framework.

Q: How do I grow embothrium in the UK?

Embothrium grows in acid, humus-rich, moisture-retentive (but not waterlogged), free-draining soil in partial shade to full sun, sheltered from cold north and east winds; it will not grow on alkaline, chalky, or dry soils. The soil requirement is non-negotiable: embothrium in neutral or alkaline soil turns progressively chlorotic (yellow between the veins), produces curled, stunted leaves, declines, and eventually dies; no amount of feeding or watering will compensate for an unsuitable soil pH. Aim for pH 5.0 to 6.0 (acid). Preparation of the planting area is the single most important step: in suitable acid soil areas, prepare a large planting hole (at least 60 cm wide and deep) and improve the soil with copious amounts of leafmould, well-rotted pine bark, or ericaceous compost to create a deep, moist, humus-rich, free-draining root zone. In gardens with slightly too-alkaline soil, building a large raised bed filled entirely with ericaceous compost can allow embothrium to be grown where it would otherwise fail, though this requires long-term commitment to maintaining the bed's acid conditions. Position in partial shade (dappled light through a canopy of light-branched trees) to full sun; in the wetter parts of the UK, full sun exposure produces the most abundant flowers. Mulch heavily with pine bark or leafmould every spring to conserve moisture, maintain the acid soil conditions, and suppress weeds. Embothrium does not need regular feeding; a light application of ericaceous slow-release fertiliser in April is sufficient. Do not prune unless absolutely necessary; embothrium does not regenerate reliably from old wood and should be planted in a position with sufficient space to develop naturally.

Q: Why is my embothrium not flowering?

Embothrium coccineum can take several years after planting to produce its first significant flower display; young plants (under 3 to 5 years old) often produce little or no flower in their early years even in ideal conditions, and this is normal. Once the plant is established and has built up a sufficient framework of mature stems, the flower display improves rapidly year on year. Common reasons for an established embothrium failing to flower well include: soil pH too high (even slight alkalinity reduces flowering and vigour; test the pH and correct if necessary); too much shade (embothrium in dense shade produces few or no flowers; a more open or partially shaded position is needed); late spring frost damage to developing flower buds (hard frosts in April and May can kill the developing buds before they open, resulting in a partial or absent display in that season); drought stress in the previous summer (the flower buds for the current year's display develop the previous summer; drought stress in July to September of the prior year can reduce the following season's flower crop substantially); or cold damage to the flowering stems in winter. In areas of the UK where summer rainfall is adequate and the soil pH is correct, embothrium typically flowers reliably and abundantly from about the fifth year of establishment and becomes increasingly spectacular each subsequent year as the plant builds up more flowering wood.

Embothrium coccineum (Chilean fire bush) is one of the most spectacular flowering trees grown in UK gardens: in late May and June, established plants in mild, sheltered positions with acid soil produce thousands of brilliant scarlet-orange tubular flowers. The soil requirement is absolute; alkaline or chalky soil causes chlorosis and leaf curl that cannot be corrected. Drought stress and cold damage are secondary causes; the plant is most reliable in the mild, wet west of the UK.

Alkaline soil

Alkaline or neutral soil is the most common reason embothrium fails and its leaves turn yellow, curl, and become stunted in UK gardens outside the naturally acid-soil regions of the west and north. Embothrium is a calcifuge (lime-hating) plant from acid, peaty South American soils; in soils above about pH 6.5 it cannot absorb iron and magnesium efficiently, leading to interveinal chlorosis (yellowing between the leaf veins), progressive weakening, leaf curl, and eventually decline and death. No amount of watering, feeding, or other care will compensate for an incorrectly alkaline soil. The problem is terminal without a fundamental change to the growing medium.

What to do

Test soil pH before planting; target pH 5.0 to 6.0. In naturally acid-soil gardens, prepare the planting hole with leafmould or composted pine bark to maintain the acid environment. In gardens with neutral or slightly alkaline soil, build a large raised bed (minimum 90 cm deep and 120 cm wide) filled entirely with ericaceous compost as a permanent acid growing medium; maintaining long-term soil acidity in an alkaline environment requires ongoing management. Water only with rainwater (collected in a water butt); tap water in hard-water areas is alkaline and progressively raises the pH of raised-bed ericaceous growing media. Never attempt to grow embothrium directly in alkaline soil; the plant will decline and die.

Drought stress

Embothrium is native to the high-rainfall areas of Chilean Patagonia and is not adapted to dry summers; the long, glossy, leathery leaves curl inward along their length and the plant looks wilted in dry spells. Drought is most problematic on free-draining acid soils in areas of lower rainfall (eastern Scotland, eastern England), and in the first seasons after planting before the root system is deeply established. The previous summer's moisture availability also affects next year's flowering; drought stress in July to September reduces the flower bud set for the following season.

What to do

Mulch heavily with pine bark or leafmould (15 to 20 cm deep) every spring; extend the mulch well beyond the root zone. Water during dry spells, particularly in the first two to three seasons after planting; established plants in the wetter parts of the UK rarely need supplementary watering. Collect rainwater in water butts for watering in hard-water areas; alkaline tap water harms the soil acid balance over time.

Cold damage

Cold damage browns and curls the leaves and kills shoot tips in hard UK winters; the semi-evergreen leaves of the 'Norquinco Valley' form may be partially or fully shed in cold winters, and the plant regrows from surviving wood or from the base. Late spring frosts in April and May can damage or kill the developing flower buds, resulting in a partial or absent display in that season even when the plant is otherwise healthy. Embothrium is most reliable in the mild, wet west of the UK where severe frosts are uncommon.

What to do

Plant in the most sheltered position available; shelter from north and east winds is more important than frost protection, as cold wind desiccates and kills the large leaves rapidly. In colder UK areas, wrap young plants in horticultural fleece from November to March. Do not prune cold-damaged growth until May when the extent of surviving growth is clear; embothrium regenerates from living buds, but does not break reliably from very old wood.

Waterlogging

While embothrium needs a moist, humus-rich growing medium, it does not tolerate standing water or completely saturated, waterlogged soils; the roots need some soil aeration to function, and prolonged waterlogging causes root rot, leaf yellowing, and collapse. This is a rare problem in naturally free-draining acid soils, but can occur in heavy clay soils that have been amended with ericaceous compost without adequate underlying drainage.

What to do

Ensure the planting position has good underlying drainage even if the surface soil is moisture-retentive. In heavy soils, break up any compacted layers below the planting hole. If building a raised ericaceous bed, ensure there is free drainage through the bottom of the structure; add a layer of coarse gravel at the base to improve drainage.

Frequently asked questions

Why are my embothrium leaves curling?

Embothrium leaves curl most commonly because of alkaline or neutral soil (the plant requires acid pH 5.0 to 6.0; any deviation causes chlorosis and leaf curl that eventually kills the plant), drought stress (the long leathery leaves curl inward in dry conditions; water and mulch deeply), or cold damage (frost kills shoot tips and the leaves brown and curl; the plant regrows from surviving wood). Alkaline soil is the most common cause of failure in UK gardens outside naturally acid-soil areas.

Is embothrium hardy in the UK?

The hardiest form, 'Norquinco Valley', survives to about -10 to -15°C in sheltered conditions and is reliably perennial in the mild, wet western UK (western Scotland, Ireland, Wales, Cornwall, Devon) where it can eventually reach tree proportions. In drier, colder areas of the UK it is less reliable. Cold wind is more damaging than frost alone; shelter is essential. The plant is semi-evergreen in most UK conditions.

How do I grow embothrium in the UK?

Grow in acid (pH 5.0 to 6.0), humus-rich, moisture-retentive but well-drained soil, in a sheltered position in partial shade to full sun. Prepare the planting area generously with leafmould or ericaceous compost; mulch deeply every spring. Do not use alkaline tap water in hard-water areas; collect rainwater instead. The plant does not need pruning and does not regenerate reliably from old wood. Spectacular results are most reliably achieved in western Scotland, Ireland, and the south-west.

Why is my embothrium not flowering?

Young plants (under 5 years old) often produce little or no flower; this is normal. Common causes in established plants: soil pH too high (even mild alkalinity suppresses flowering); too much shade; late spring frost damage to developing buds; or drought stress in the previous summer (July to September) reducing flower bud set. In acid soil, moist conditions, and adequate shelter, embothrium becomes increasingly spectacular year on year once established.