Plant problems

Why Are My Mitraria Leaves Curling?

Q: Why are my mitraria leaves curling?

Mitraria coccinea (mitre flower) leaves curl and drop most commonly in UK gardens because of drought stress (mitraria comes from cool, moist, acid Andean and Chilean coastal forest and requires consistent moisture; the small, glossy, dark green leaves curl when the root zone dries out), alkaline or chalky soil (mitraria is an ericaceous plant that cannot tolerate alkaline conditions; the leaves yellow from lime-induced chlorosis, curl, and drop), or cold damage in hard UK winters (mitraria is only moderately hardy and the foliage and stems can be damaged by hard frost below about -8 to -10°C in exposed conditions). Mitraria coccinea is a scrambling, spreading evergreen shrub or sub-shrub (often grown as a lax climber against a wall or through a supporting shrub) with small, glossy, dark green, toothed leaves and distinctive pendant, tubular, bright orange-scarlet flowers produced over a very long season from late spring (May to June) through summer and into autumn (September to October); in mild conditions and sheltered positions, flowering may extend even longer. The flowers are large relative to the small leaves of the plant and are a remarkable and vivid scarlet-orange that makes the plant highly visible in the garden when in bloom. Mitraria is a member of the Gesneriaceae family (the same family as gloxinia and African violet) and is the sole species in its genus; it is native to southern Chile and adjacent Argentina, primarily in the Valdivian temperate rain forest, one of the most biodiverse temperate forests in the world. The plant is closely related to other southern hemisphere gesneriad shrubs and climbers including Asteranthera, Sarmienta, and Codonoboea.

Q: Is mitraria hardy in the UK?

Mitraria coccinea is moderately hardy in the UK; it is generally considered hardy to approximately -8 to -10°C in a sheltered position against a wall or in a well-protected woodland border, and is reliably perennial in the mildest UK gardens (sheltered coastal and urban positions in the south-west, western Scotland, western Ireland, and mild urban positions in London and similar cities). In colder UK areas (north of England, Scotland away from the coast, high altitude, exposed positions), mitraria is less reliable and may be killed in hard winters. The plant is hardier when grown in the conditions it prefers: cool, moist, acid soil in a sheltered, semi-shaded position produces harder, healthier growth that withstands cold better than the lush, soft growth produced in warm, sunny, over-watered conditions. Like desfontainia and other Valdivian forest plants, mitraria is considerably less cold-sensitive than its native range (extreme southern South America) might suggest; the Valdivian forest experiences a cool but not severely cold maritime climate, and the plants from this habitat are adapted to cool, moist conditions rather than to frost resistance. The most favourable UK conditions for mitraria closely resemble those for desfontainia: sheltered, lightly shaded, consistently moist, acid soil, in the wetter, milder parts of the UK. Western Scotland, in particular, offers near-ideal conditions for both plants.

Q: How do I grow mitraria in the UK?

Mitraria coccinea grows best in a sheltered, lightly shaded position in consistently moist, acid (pH 4.5 to 6.0), humus-rich, freely draining soil; a cool, moist position at the foot of a wall in light shade, or in a woodland garden with acid, leaf-mould-enriched soil, provides ideal conditions. The plant is often trained against a shaded north or west-facing wall, or allowed to scramble through a supporting acid-loving shrub (such as a rhododendron or a camellia) where it receives some shade from the support plant. It can also be grown effectively as a ground-cover plant in shaded, moist conditions, where its lax, scrambling stems root as they creep along the surface; this is a natural growth habit in its native Valdivian forest, where it scrambles and roots over the forest floor. Add leaf mould, composted bark, or ericaceous compost to improve soil acidity and moisture retention. Water with rainwater in hard-water areas; tap water in alkaline areas gradually raises pH and harms the plant. Mulch annually with leaf mould or composted bark to maintain soil moisture and acidity. The plant is slow to establish but once settled in the right conditions it grows steadily and produces an abundant, long-lasting flower display; the brilliant orange-scarlet tubular flowers are very striking in the semi-shaded conditions in which mitraria grows best, where the intensity of colour seems heightened by the contrast with the surrounding shade.

Q: Why is my mitraria not flowering?

Mitraria flowers over a very long season (May to October in favourable conditions) on established plants; poor or absent flowering is most commonly caused by alkaline soil (progressively weakens the plant and reduces flowering; acid, humus-rich conditions are needed), drought stress (water stress during the growing season reduces flower bud formation; consistent moisture is essential), too much deep shade (some shade is beneficial, but dense, deep shade suppresses flowering; light dappled shade or bright indirect light is optimal), or cold damage to the flowering stems in winter (hard frost kills the stems that carry the following season's flowers; in cold UK areas, winter protection is needed to preserve the flowering wood). In the right conditions, mitraria produces a remarkable flowering display: the pendant, vivid scarlet-orange tubular flowers hang from the scrambling stems over several months, providing colour from late spring through autumn in a position where few other plants of comparable ornamental value would survive. The plant is rarely seen at its best in the UK outside the mildest, wettest gardens, but in those gardens it is spectacular; it was introduced to UK gardens in the 1840s and has been grown at Caerhays and other Cornish and Scottish woodland gardens since that period.

Mitraria coccinea (mitre flower) is a scrambling, lax evergreen shrub from the Valdivian temperate rainforests of southern Chile, grown for its brilliant long-tubed scarlet-orange flowers produced from May to October. It needs cool, moist, acid conditions; sheltered, lightly shaded woodland gardens in western Scotland and the south-west of England suit it best. Drought stress and alkaline soil are the most common causes of leaf curl and decline.

Drought stress

Drought stress causes the small, glossy, dark green leaves of mitraria to curl inward and drop; the plant comes from one of the wettest temperate forests in the world and has no drought tolerance whatsoever. Even brief drying out causes visible stress; prolonged drought causes complete leaf drop and may kill the plant. The combination of drought and hot sun is the most rapidly damaging scenario. Container-grown mitraria is particularly vulnerable; the plant is best grown in the ground in moist, acid conditions.

What to do

Water consistently; mitraria must never be allowed to dry out at the root. Mulch deeply with leaf mould or composted bark. Use rainwater in hard-water areas. Position in lightly shaded, cool conditions where moisture is retained; a shaded wall base, woodland edge, or sheltered north-facing position all reduce moisture loss. Drip irrigation or buried seep hose maintains the consistent moisture the plant requires without wetting the foliage.

Alkaline soil

Alkaline soil is fatal to mitraria over time; the plant is an ericaceous species that requires acid conditions (pH 4.5 to 6.0) and cannot extract iron, manganese, or other micronutrients from alkaline soil. Progressive yellowing between the veins (lime-induced chlorosis), leaf curl, and plant decline follow planting in alkaline ground. The problem cannot be fully resolved by foliar feeding; the soil or growing medium itself must be acidic.

What to do

Test soil pH before planting; use ericaceous compost and acid leaf mould. In alkaline gardens, grow in a large raised bed of ericaceous compost. Water with rainwater only; tap water in alkaline areas gradually raises pH. Apply a sequestered iron feed in spring to treat existing chlorosis while underlying conditions are addressed.

Cold damage

Cold damage browns and drops the leaves of mitraria in hard UK winters; temperatures below about -8 to -10°C in exposed conditions can kill the stems. The plant is most vulnerable in dry, cold conditions; moist, acid soil and shelter from freezing winds reduce cold damage significantly. In western Scotland, mild winters and the naturally moist, sheltered conditions of woodland gardens allow mitraria to grow successfully as a permanent, established shrub; in drier, colder parts of the UK the plant is borderline and may be cut back in hard winters.

What to do

Grow in a sheltered position; a wall base, sheltered woodland clearing, or the north or west face of a building all provide frost amelioration. Wrap in fleece from November to March in colder UK areas. Do not cut back until April; surviving buds may be concealed in apparently bare stems. Take semi-ripe cuttings in July to August as insurance against winter losses.

Frequently asked questions

Why are my mitraria leaves curling?

Mitraria leaves curl most commonly because of drought stress (the plant needs consistent moisture and has no drought tolerance; mulch deeply and water regularly with rainwater), alkaline soil (causes yellowing and curl from lime-induced chlorosis; needs pH 4.5 to 6.0; grow in ericaceous compost in alkaline gardens), or cold damage in hard winters (stems and foliage damaged below -8°C; shelter and moist acid soil reduce cold sensitivity). The Valdivian forest is one of the wettest habitats on earth; replicating that moisture is the key.

Is mitraria hardy in the UK?

Mitraria is hardy to about -8 to -10°C in sheltered, moist conditions and is reliably perennial in mild UK gardens (western Scotland, south-west England, mild urban positions). In colder areas it may be cut back in hard winters but often regrows from the base. Consistent moisture and acid soil are more important for survival than winter temperatures alone; a plant in the right conditions withstands cold significantly better than a stressed plant.

How do I grow mitraria in the UK?

Grow in a cool, sheltered, lightly shaded position in consistently moist, acid (pH 4.5 to 6.0), humus-rich soil; a shaded north or west-facing wall base, or a position in a lightly shaded woodland garden, is ideal. Train against a wall or allow to scramble through a supporting acid-loving shrub such as a rhododendron. Mulch annually with leaf mould; water with rainwater. Take semi-ripe cuttings annually as winter insurance.

Why is my mitraria not flowering?

The most common causes of poor flowering are alkaline soil (weakens the plant and suppresses flower production; acid conditions are essential), drought stress (water stress reduces flower bud formation; consistent moisture throughout the growing season is needed), deep shade (some shade is beneficial; dense shade suppresses flowering), or cold damage to flowering stems in winter (winter protection preserves the flowering wood in colder UK areas). In the right conditions, the brilliant scarlet-orange tubular flowers are produced from May to October on established plants.