Plant problems

Why Are My Anemanthele Leaves Curling?

Q: Why are my anemanthele leaves curling?

Anemanthele lessoniana (pheasant's tail grass, formerly classified as Stipa arundinacea) leaves curl, brown at the tips, and develop a dishevelled appearance most commonly in UK gardens because of cold damage in hard winters (anemanthele is borderline hardy in most of the UK; the characteristic orange-bronze, fine-textured, arching leaves that develop their most vivid colouring in autumn and early winter are damaged by sustained frost below about -8 to -10°C in freely draining conditions; in cold, wet conditions, the damage threshold is lower and even milder UK winters can cause significant leaf damage if the crown sits in saturated soil), drought stress in summer (the very fine, arching leaves curl along their length when the root zone dries out; container-grown plants and those in very sandy or shallow soils in a hot UK summer are most at risk), or the natural cycle of leaf die-back at the base of the clump (anemanthele, like stipa tenuissima, goes through an annual cycle where older leaves at the base of the clump brown, matt, and accumulate; this is normal and managed by the annual spring tidy, not a symptom of a cultural problem). Anemanthele lessoniana is a species of a single-species genus from New Zealand grown in UK gardens for its extraordinarily beautiful autumn and winter foliage colouring: the fine-textured, arching, green leaves that emerge in spring gradually develop vivid orange, copper, and bronze tints from mid-summer through autumn, deepening as temperatures fall; the colour intensity peaks in November and December and makes anemanthele one of the most distinctive and colourful grasses available for UK gardens.

Q: Is anemanthele hardy in the UK?

Anemanthele lessoniana is borderline hardy in the UK and its cold tolerance varies significantly with drainage and position; in freely draining, gritty soil in a sheltered, sunny position, it tolerates temperatures to approximately -8 to -10°C and can be grown outdoors year-round in most UK gardens except the coldest, most exposed upland sites. In wet, poorly draining conditions, the cold tolerance is much lower and even a relatively mild UK winter with sustained cold and wet can damage or kill the plant. In the mildest UK areas (coastal Cornwall, coastal west Ireland, Channel Islands, sheltered London gardens) anemanthele is reliably evergreen and perennial outdoors; in colder or wetter UK inland gardens, it is more reliable if given a sheltered, south-facing position in freely draining, gritty soil with a dry bark or gravel mulch from November. Container growing in a very free-draining compost moved under frost-free cover from November to March is the most reliably safe approach in cold or wet UK gardens, but many gardeners successfully grow it in the ground in sheltered UK positions and accept that a severe winter may cause significant die-back that regrows from the crown in spring. The vivid autumn colouring is best in a sunny position; in deep shade, the autumn colour development is reduced.

Q: How do I grow anemanthele in the UK?

Anemanthele grows best in a warm, sunny, sheltered position in freely draining, moderately fertile, slightly acid to neutral soil; a south or south-west facing position at the base of a warm wall or in a sheltered courtyard, or a raised bed with gritty, lean growing medium, gives the best results and the most cold-tolerant plants. Sun is important both for cold tolerance (plants in sun develop harder, more compact growth than those in shade) and for autumn colour development (the vivid orange and bronze tints develop most intensely in a sunny position; in shade, the colouring is more muted). Plant in spring (April to May) after the coldest weather has passed. Water consistently through the first growing season to establish the root system; once established, anemanthele in a reasonably moist, free-draining UK soil is largely self-sufficient. Apply a dry bark or gravel mulch around the crown from November to insulate the root zone from the worst winter cold and wet. The annual management requirement is: cut back or comb out accumulated dead leaves in late February or early March before new growth begins; do not cut back the living green and orange leaves, only the matted brown dead material at the base. The plant can also be cut back hard to 5 to 8 cm in late winter and it regenerates well. Divide in spring every three to four years to refresh the clump and propagate new plants.

Q: Why does anemanthele turn orange in autumn?

The extraordinary autumn colour of Anemanthele lessoniana is produced by the accumulation of carotenoid pigments (responsible for orange and yellow tones) as the leaves age and begin their senescence process in cooler autumn temperatures; the colour change is accelerated and intensified by cool night temperatures, bright autumn sunshine, and some moisture stress, creating the vivid orange-copper-bronze tints that make this grass so distinctive from August to January. The process is similar to autumn leaf colour in deciduous trees: as temperatures fall and day length shortens, the green chlorophyll in the leaves degrades, revealing the underlying carotenoid pigments which had been masked through the growing season. Unlike deciduous trees, anemanthele does not fully shed its leaves in autumn; the coloured leaves persist through winter, providing ornamental interest when most garden plants are dormant. The colour intensity varies by position: plants in full sun develop the most vivid orange tints, while those in shade remain more green throughout autumn and winter. In mild, wet UK autumns with little temperature fluctuation, the colour development can be less spectacular than in autumns with cold, clear nights; this is why anemanthele sometimes fails to colour as expected in a particularly mild UK October or November.

Anemanthele lessoniana (pheasant's tail grass) is a New Zealand grass prized for its extraordinary autumn and winter colour: the fine, arching leaves develop vivid orange, copper, and bronze tints from late summer, deepening through November and December. Borderline hardy in the UK; grows best in a warm, sunny, sheltered position in free-draining soil. Cold in wet conditions and summer drought are the primary causes of leaf curl and browning.

Cold damage

Cold is the most common cause of serious anemanthele problems in UK cultivation; sustained frost below about -8°C in freely draining conditions, or milder frost in wet, poorly draining soil, causes the fine leaves to curl, brown, and collapse. In a hard UK winter, the entire above-ground growth may be killed while the crown and roots survive to regenerate in spring. Cold combined with wet is far more damaging than cold in dry, free-draining conditions.

What to do

Grow in a sheltered, south-facing position in very freely draining, gritty soil; apply a dry bark or gravel mulch around the crown from November to insulate the root zone. In cold UK gardens, move container-grown plants under frost-free cover from November to March. Do not cut back frost-damaged growth until late April; even dead-looking top growth provides some insulation to the crown through the coldest months. If the crown is alive in spring (green at the base), cut back hard to 5 to 8 cm and the plant regenerates.

Drought stress

The very fine, arching leaves curl inward when the root zone dries out; container plants and those in shallow, sandy soil in a hot UK summer are most at risk. Drought in the first growing season after planting is particularly damaging as the root system has not yet developed the depth to access deeper soil moisture. The drought response in anemanthele is visible quickly and the leaves recover within a day of thorough watering if the damage is not yet browning.

What to do

Water consistently through the first growing season; once established, anemanthele in a reasonable UK soil is largely drought-tolerant and needs supplementary watering only during prolonged dry spells. Apply a bark mulch to retain soil moisture and maintain root zone temperature. Container plants need daily checking in hot summer weather; water when the top few centimetres feel dry.

Natural leaf die-back

Anemanthele accumulates dead leaves at the base of the clump naturally through the season; the inner and lower leaves age, brown, and mat within the clump while the outer and upper leaves remain colourful and ornamental. This natural die-back is more pronounced after a hard winter and in late summer before the new season's colour develops. It is managed by the annual spring tidy rather than being a symptom of a cultural problem.

What to do

In late February or early March, comb out dead and brown leaves from the base of the clump using fingers or a fine-tined rake; this removes accumulated dead material without damaging the living leaves. Alternatively, cut the entire clump back hard to 5 to 8 cm from the base; it regenerates well and the new growth often develops better colour than old accumulated foliage. Repeat annually for the best appearance.

Frequently asked questions

Why are my anemanthele leaves curling?

Anemanthele leaves curl most commonly because of cold damage in hard or wet winters (below -8°C in dry conditions; mulch the crown from November; move containers under cover; leave damaged growth until April), drought stress in summer (fine leaves curl quickly when roots dry; water in dry spells; mulch; consistent moisture through the first season), or natural leaf die-back at the base of the clump (normal ageing; comb out or cut back to 5 to 8 cm in late February annually). Shelter, free drainage, and sun are the keys to success.

Is anemanthele hardy in the UK?

Anemanthele is borderline hardy; in freely draining, gritty soil in a warm, sheltered, sunny position it tolerates approximately -8 to -10°C and grows outdoors year-round in most UK gardens. In wet or poorly draining conditions, the threshold is much lower. In mild UK gardens (coastal Cornwall, west Ireland, sheltered London) it is reliably evergreen. In colder or wetter inland gardens, container growing moved under frost-free cover from November is the safest approach.

How do I grow anemanthele in the UK?

Grow in a warm, sunny, sheltered south or south-west facing position in freely draining, moderately fertile, slightly acid to neutral, gritty soil. Apply a bark or gravel crown mulch from November. Water through the first season; largely self-sufficient once established. Comb out dead leaves in late February or cut back hard to 5 to 8 cm. Divide every three to four years in spring. The vivid orange-bronze autumn colour develops most intensely in full sun with cool autumn nights.

Why does anemanthele turn orange in autumn?

The orange-copper-bronze autumn colour is produced by carotenoid pigments revealed as the green chlorophyll degrades in cooler autumn temperatures; the process is similar to autumn tree colour. Cool night temperatures and bright autumn sunshine intensify the colour most. In full sun the colour is most vivid; in shade it remains more green. In mild, wet UK autumns with little temperature fluctuation, colour development can be less spectacular than in cold, clear autumns. The coloured leaves persist through winter, providing ornamental interest when most plants are dormant.