Plant problems

Why Are My Crinodendron Leaves Curling?

Q: Why are my crinodendron leaves curling?

Crinodendron hookerianum (Chilean lantern tree) leaves curl and yellow most commonly in UK gardens because of alkaline or neutral soil (crinodendron requires distinctly acid, humus-rich soil and cannot absorb iron in alkaline conditions, leading to chlorosis and leaf curl), drought stress (the evergreen leaves curl and the buds fail to develop in dry conditions), or cold damage in hard UK winters (the evergreen leaves are damaged by hard frost and cold drying wind, developing brown curled margins). Crinodendron hookerianum is one of the most striking flowering evergreen shrubs or small trees that can be grown in UK gardens: in April and May, established plants in suitable conditions are covered with scores to hundreds of pendant, deep crimson-red, lantern-shaped flowers on long stalks from the leaf axils of the previous year's growth, creating a display that is genuinely unlike any other UK-hardy plant. It is native to moist, temperate rainforest in southern Chile and grows naturally in deep, humus-rich, acid, constantly moist soil under light tree canopy; this defines the conditions it needs in UK gardens precisely. Crinodendron is most successful in the mild, moist, acid-soil gardens of western Scotland, Ireland, Wales, and south-west England where the combination of mild winters, high rainfall, acid soils, and humid air most closely replicates its native environment; in drier, colder, or less acid parts of the UK it is challenging to grow well. The closely related Crinodendron patagua produces white, urn-shaped flowers in summer and is slightly more tolerant of drier conditions and marginally higher pH, but is less widely grown in the UK.

Q: Is crinodendron hardy in the UK?

Crinodendron hookerianum is marginally hardy in the UK; it is generally considered hardy to about -8 to -10°C in ideal conditions (sheltered, humid, mild garden) and is reliably perennial in the mildest parts of the UK (western Scotland, where it is particularly associated with famous gardens including Crarae, Inverewe, Glenarn, and the Logan Botanic Garden; western Ireland; mild coastal and urban gardens in Wales and the south-west of England). In colder, drier parts of the UK (east of England, exposed inland gardens, northern England), crinodendron is not reliably hardy and may be killed or severely damaged in hard winters; it can be grown in containers and overwintered under glass in such areas, but in-ground cultivation is precarious. Cold wind is at least as damaging as frost for crinodendron: the large, leathery, evergreen leaves desiccate rapidly in cold dry wind, causing brown curled margins and tips that look similar to frost damage. The combination of cold air, cold soil, and cold drying wind in a continental-type UK winter is far more damaging than the same temperature in a maritime, humid environment with the same frost threshold. This is why crinodendron is so much more reliable in the oceanic west of the UK than the figures for frost hardiness alone would suggest: the western UK maritime climate keeps temperatures above hard-freeze level far more often AND provides the humidity that prevents leaf desiccation. Crinodendron patagua is considered slightly hardier than C. hookerianum and is worth trying in areas where the red-lantern species has been marginal.

Q: How do I grow crinodendron in the UK?

Crinodendron hookerianum grows in acid (pH 5.0 to 6.0), humus-rich, moisture-retentive but well-drained soil in a sheltered position in partial shade; it does not grow in alkaline or chalky soil, does not tolerate drought, and does not tolerate cold drying wind. The planting position is the most important decision: choose the most sheltered available spot, preferably at the edge of a light woodland canopy where the plant is sheltered from wind, receives dappled to full light (it is surprisingly tolerant of shade and can flower well under quite a dense overhead canopy), and the roots remain consistently moist. Prepare the planting area very generously with leafmould, composted pine bark, and well-rotted garden compost to create a deep, humus-rich, acid growing medium; the root zone should be airy, moist, and rich in organic matter. Mulch the surface deeply (15 cm of pine bark or leafmould) and renew the mulch annually; the roots of crinodendron are shallow and surface roots benefit from consistent protection from drying and frost. Water in dry spells using rainwater if possible; in hard-water areas, tap water gradually raises the soil pH and reduces the plant's ability to absorb essential nutrients. Feed lightly with an ericaceous fertiliser in April; crinodendron does not need heavy feeding and excess fertility (particularly excess nitrogen) produces lush, soft growth that is more vulnerable to cold damage and produces fewer flowers. Crinodendron flowers on the previous year's wood; the crimson buds form on the previous season's stems in summer and swell and open in April to May the following year. Do not prune in autumn or winter, which removes the developing flower buds. Prune only after flowering (June) if necessary; remove any dead or damaged stems to healthy wood.

Q: Why is my crinodendron not flowering?

Crinodendron hookerianum flowers on the previous season's wood; the deep crimson buds form on the stems during the preceding summer and swell and open in April to May. Common reasons for an established crinodendron failing to flower include: cold damage to the developing buds in winter (temperatures below -8 to -10°C, or cold drying wind, kill the swelling buds before they can open; the following spring the plant appears healthy but with few or no flowers); incorrect pruning (pruning in autumn, winter, or early spring removes the buds that were developing on the previous year's stems; prune only in June after flowering); soil pH too high (alkalinity progressively weakens the plant and reduces its ability to form flowers; test and correct the soil pH); drought stress in the previous summer (the buds form on the current season's shoots in summer; drought stress in July to August reduces the quantity of buds formed for the following year's display); or the plant being too young (young, recently planted crinodendron may take 3 to 5 years to build up enough of a mature framework to produce an abundant flower display). In the correct conditions (acid, moist, humus-rich soil; sheltered, humid; mild maritime UK climate), an established crinodendron in a mild western garden is one of the most reliably spectacular flowering shrubs in April and May; the crimson pendant lanterns covering the plant are extraordinary.

Crinodendron hookerianum (Chilean lantern tree) is a spectacular evergreen shrub or small tree that covers itself in pendant, deep crimson, lantern-shaped flowers in April and May. It requires acid, humus-rich, consistently moist soil and shelter from cold wind; alkaline soil is the most common reason it fails. Most reliable in the mild, wet west of the UK where conditions match its native Chilean rainforest environment.

Alkaline soil

Alkaline or neutral soil is the most common cause of crinodendron failure in UK gardens outside naturally acid-soil areas. Crinodendron cannot absorb iron efficiently in soil above about pH 6.5, causing interveinal chlorosis (yellowing between the leaf veins), leaf curl, and progressive decline. The condition cannot be corrected by feeding or watering; only growing the plant in genuinely acid soil resolves it. Target pH 5.0 to 6.0; test before planting.

What to do

Prepare a large planting hole with generous quantities of leafmould, composted pine bark, and ericaceous compost to create a deep acid growing medium. In gardens with neutral or alkaline soil, a large raised bed filled entirely with ericaceous compost is the only reliable approach; water only with collected rainwater as alkaline tap water raises pH over time. Apply iron chelate sequestrant if chlorosis develops in marginally suitable soil. Never plant crinodendron in alkaline or chalky soil.

Drought stress

Crinodendron is native to the extremely high-rainfall temperate rainforest of southern Chile and does not tolerate dry conditions; the evergreen leaves curl, the developing flower buds fail to swell, and the plant looks stressed and unhappy when the root zone dries out. Drought is a particular problem in lower-rainfall areas of the UK (east of England, drier parts of the south-east) and in the first seasons after planting before the root system is deeply established. The previous summer's moisture availability directly affects next spring's flower display, as the buds form on the current season's stems in July to August.

What to do

Mulch very deeply (15 cm of pine bark or leafmould) every spring; renew the mulch annually. Water during dry spells; use rainwater in hard-water areas. The light canopy of a woodland garden edge position creates humidity and reduces leaf moisture loss while allowing the roots to remain consistently moist. Collect rainwater in water butts for supplementary watering throughout the season.

Cold damage and wind scorch

Cold damage and cold wind desiccation turn the leathery evergreen leaves brown and curl the margins; temperatures below -8 to -10°C, and particularly cold drying wind in winter, cause the most damage. Cold wind is often more harmful than frost per se: the leaves lose moisture rapidly in dry, cold wind and cannot replace it from frozen soil, producing browning and curling very similar to frost damage. The developing flower buds on the previous year's stems are vulnerable to hard frost in January and February; bud kill results in a flowerless spring on an otherwise healthy plant.

What to do

Shelter from north and east winds is essential; a woodland edge or sheltered wall position is ideal. In colder UK areas, wrap young plants in horticultural fleece from November to March. Do not prune until June after flowering; winter pruning removes the developing buds. The plant recovers well from moderate cold damage in mild western UK gardens; new growth in spring conceals most winter-damaged foliage.

Frequently asked questions

Why are my crinodendron leaves curling?

Crinodendron leaves curl most commonly because of alkaline soil causing lime-induced chlorosis (yellowing between veins and curled margins; cannot be corrected without changing to acid growing medium), drought stress (the evergreen leaves curl and buds fail to develop when the root zone dries out; mulch and water with rainwater), or cold wind desiccation and frost damage (brown curled leaf margins in winter; plant recovers in spring in mild gardens). Acid, moist, sheltered conditions are the three non-negotiable requirements.

Is crinodendron hardy in the UK?

Crinodendron hookerianum is hardy to about -8 to -10°C in sheltered, humid conditions and is reliably perennial in the mild, wet western UK (western Scotland, Ireland, Wales, south-west England). Cold drying wind is as damaging as frost; shelter is essential. In colder, drier parts of the UK it can be grown in containers and overwintered under glass. The plant is most associated with famous west-coast Scottish gardens where it can reach tree proportions.

How do I grow crinodendron in the UK?

Grow in acid (pH 5.0 to 6.0), humus-rich, consistently moist but well-drained soil in a sheltered position in partial shade. Prepare the planting area very generously with leafmould and ericaceous compost; mulch 15 cm deep annually; water with rainwater in hard-water areas. Prune only in June after flowering; never prune in autumn or winter. The woodland garden edge is the classic position. The crimson pendant lanterns in April and May are extraordinary on an established, well-grown plant.

Why is my crinodendron not flowering?

The most common causes: cold damage to buds in winter (temperatures below -8°C or cold drying wind kill the swelling buds before April); pruning at the wrong time (only prune in June, never in autumn or winter); soil pH too high (alkalinity weakens the plant and reduces bud formation); drought stress the previous summer (buds form in July to August; drought reduces the following year's display); or the plant being too young (allow 3 to 5 years to build up a mature framework).