Plant problems

Why Are My Puya Leaves Curling?

Q: Why are my puya leaves curling?

Puya (giant bromeliad or Chilean bromeliad) leaves curl and brown most commonly in UK gardens because of cold damage in hard winters (puya is a borderline-hardy genus of terrestrial bromeliads from the Andes; the most commonly grown species in the UK, Puya berteroniana and Puya alpestris, are generally hardy to approximately -8 to -12°C in freely draining conditions in a sheltered position, but the rosette of narrow, recurving, spine-edged leaves curls and browns after sustained exposure to frost below about -5°C), waterlogging in poorly draining UK winter soil (puya comes from rocky, arid mountain slopes in the Andes and is extremely intolerant of sustained waterlogging; the roots rot rapidly in saturated soil, causing the leaves to yellow and curl progressively; wet and cold combined is more lethal than either factor alone), or drought stress in summer (the narrow, arching leaves curl inward along their length when the root zone dries out excessively in very dry UK summers). Puya is a genus of around 200 species of terrestrial, rosette-forming bromeliads (Bromeliaceae) from mountain habitats in South America, primarily the Andes; they range from relatively small plants to the extraordinary Puya raimondii, one of the largest flowering plants in the world (the flower spike can reach 10 m), though the UK-grown species are considerably more modest in scale. The most commonly grown species in UK gardens (P. berteroniana, P. alpestris, P. chilensis) form large, spreading rosettes of narrow, spine-edged, grey-green leaves that can reach 60 to 90 cm in length in established plants, with dramatic flower spikes of intense blue-green or yellow-orange flowers on established specimens.

Q: Is puya hardy in the UK?

Puya hardiness in the UK varies by species; Puya berteroniana and Puya alpestris are the most commonly grown and most reliably hardy species in UK gardens, generally tolerating temperatures to approximately -8 to -12°C in freely draining, open, south-facing, sheltered conditions. However, as with fascicularia and celmisia (other South American high-altitude bromeliads), the limiting factor in UK cultivation is almost never absolute cold but the combination of cold and wet; puya in heavy, wet clay soil or in a low-lying, poorly draining position is killed by conditions that the same plant in a perfectly draining, raised, south-facing scree bed would survive easily. The most reliably perennial positions for outdoor puya in the UK are: a rock garden or raised scree bed with a gritty, lean growing medium; a south-facing slope or bank with natural drainage; a raised position against a warm, south-facing wall; or a position where winter precipitation is naturally deflected away from the roots (for example, under an overhanging roof or large tree canopy that keeps the root zone dry). In all other UK conditions, puya is more reliably grown in a large container that can be moved into a frost-free or cool greenhouse from November to April.

Q: How do I grow puya in the UK?

Puya grows best in a sunny, open position in full sun in very freely draining, lean, neutral to slightly acid, gritty or rocky soil; the rock garden, raised scree bed, or a south-facing slope with skeletal, thin, gritty soil most closely approximates the Andean rocky mountain slope conditions from which the plants come. Do not add compost or feed heavily; lean conditions produce compact, cold-tolerant growth and reduce the risk of the soft, lush, frost-sensitive foliage produced by rich conditions. Apply a coarse gravel or grit mulch around each plant (10 to 15 cm deep) to prevent moisture sitting at the crown and to reduce frost penetration into the root zone. Keep the crown as dry as possible in winter; in wet UK autumns and winters, a pane of glass or clear polycarbonate propped over the plant on the windward side significantly reduces rain penetration to the crown and root zone while maintaining air circulation. Handle with care: the spine-edged leaves are sharp and the backward-pointing teeth on the leaf margins are particularly effective at catching clothing and skin when the hand or arm brushes the leaf in the wrong direction. In containers, use a very free-draining mix (one part John Innes No. 2, one part coarse grit, one part crushed stone); bring under cover from November to April in all but the mildest UK positions.

Q: When does puya flower in the UK?

Puya flowers are extremely rare in the UK; the plants require many years of establishment and a long, hot growing season to build sufficient energy for flower spike production, and UK summers are typically not warm enough or long enough for most puya species to reach flowering condition reliably. Puya berteroniana and P. alpestris are the most likely species to flower in UK garden conditions in the warmest, most sheltered south or south-west coast gardens; reports of these species flowering outdoors in the UK exist but are exceptional rather than routine. In specialist collections (Chelsea Physic Garden, RHS Wisley, and other botanic gardens with large glass structures or very sheltered outdoor conditions) puya has flowered occasionally, producing a dramatic spike of vivid blue-green or orange-yellow tubular flowers that are pollinated in their native South America by birds. In the typical UK garden, puya is grown as an architectural foliage plant for its bold, spiny, silver-green rosette effect rather than for its flowers; the expectation of flowering in outdoor UK conditions should be set very low. In warmer UK years with a long hot summer, puya grown in a very sheltered, south-facing, raised, sunny position may occasionally produce a flower spike, but this should be regarded as an unexpected bonus rather than a planned feature.

Puya is a genus of dramatic, spiny-leaved, terrestrial bromeliads from the high Andes with bold, grey-green rosettes of narrow, recurving, spine-edged leaves and (rarely in the UK) extraordinary flower spikes of blue-green or orange-yellow tubular flowers. Borderline hardy in most of the UK, requiring perfectly draining, lean soil in a very sheltered, sunny position. Cold combined with wet is the main cause of failure.

Cold damage

Hard frost below about -5°C causes the narrow, spine-edged leaves of puya to curl, bleach, and eventually brown and collapse; in a very hard UK winter, the entire above-ground rosette may be killed while the root system survives to resprout. The central growing point at the base of the rosette is harder than the outer leaf blades; in a partially damaged plant, new growth from the centre is often possible in spring even after severe outer leaf damage. Cold combined with persistent wet is the most dangerous condition.

What to do

Apply a deep grit and dry bark mulch (10 to 15 cm) around the base from November; in wet UK winters, prop a sheet of clear polycarbonate over the rosette to reduce rain penetration while maintaining air flow. In colder areas, grow in a large container and move under glass from November to April. Remove damaged outer leaves in spring once new growth confirms the centre is alive; do not cut back to the growing point.

Waterlogging

Puya roots rot rapidly in waterlogged, poorly aerated soil; the leaves yellow and curl progressively as the root system is destroyed. The plants come from rocky, freely draining Andean slopes where water passes through quickly; any position where water sits around the root zone for more than a few hours after rain is potentially lethal. Heavy UK clay soils and low-lying, poorly draining garden positions are the most dangerous environments for puya.

What to do

Plant only in very freely draining conditions; a raised scree bed or rock garden with 50% coarse grit in the growing medium is ideal. Apply a deep gravel collar around the base to keep the crown dry. Never plant in heavy clay without extensive drainage improvement. Container growing in a very gritty, free-draining mix is the most reliably successful approach in most UK gardens.

Drought stress

The narrow, arching leaves curl inward when the root zone dries out excessively in very hot, dry UK summers; the plants come from Andean habitats that receive seasonal rainfall and are not fully adapted to prolonged drought despite their arid-looking appearance. Container plants and those in very shallow, sandy soils are most vulnerable. The leaf curl from drought is reversible and much less damaging than the curl from cold or waterlogging.

What to do

Water at the base during prolonged dry spells in summer (June to August); allow the growing medium to approach dryness between waterings but do not allow complete desiccation. Container plants need more frequent watering than in-ground plants. Reduce watering from September onwards as the plant enters a less active growth phase.

Frequently asked questions

Why are my puya leaves curling?

Puya leaves curl most commonly because of cold damage (leaves curl and bleach below -5°C; protect with deep mulch and polycarbonate cover; container plants can go under glass), waterlogging (roots rot in saturated soil; plant in very free-draining, gritty conditions; raised scree bed or rock garden), or drought stress in summer (reversible curl; water at the base during dry spells; container plants most at risk). Cold and wet together is the most lethal combination in UK conditions.

Is puya hardy in the UK?

Puya berteroniana and P. alpestris are hardy to approximately -8 to -12°C in very freely draining, sheltered, full-sun conditions; they can be reliably perennial in sheltered south and west coast UK gardens in a rock garden or raised scree bed. In most UK garden conditions, growing in a large container moved under cover from November to April is the most reliably successful approach. Cold combined with wet is more lethal than cold alone; perfect drainage dramatically extends hardiness.

How do I grow puya in the UK?

Grow in full sun in very freely draining, lean, gritty soil; a raised scree bed, rock garden, or south-facing bank with 50% coarse grit in the growing medium is ideal. Do not add compost or fertiliser; lean conditions are essential. Apply a 10 to 15 cm gravel crown collar. Keep the crown dry in winter with a polycarbonate cover in wet conditions. Handle carefully; the backward-pointing leaf teeth are sharp. In containers, use one part John Innes No. 2, one part coarse grit, one part crushed stone.

When does puya flower in the UK?

Puya flowering in the UK is exceptional; the plants need many years of establishment and a long, hot summer to build the energy for flower spike production, and UK summers are typically too cool and short. Reports of P. berteroniana and P. alpestris flowering in sheltered south or south-west coast gardens exist but are rare. Grow puya in the UK as an architectural foliage plant; regard any flower spike as an unexpected bonus rather than a planned feature.