Plant problems

Why Are My Celmisia Leaves Curling?

Q: Why are my celmisia leaves curling?

Celmisia (New Zealand daisy or mountain daisy) leaves curl and grey most commonly in UK gardens because of waterlogging in poorly draining soil (celmisia comes from freely draining, alpine and subalpine grassland in New Zealand and cannot tolerate saturated or poorly aerated soil; the roots rot rapidly in wet conditions, causing the characteristic silver-grey leaves to curl and the plant to collapse), drought stress in very dry or hot UK summers (the silver-grey leaves curl inward along their length when the root zone dries out excessively; the grey leaf colour is an adaptation to reflect intense alpine sunlight and reduce water loss, not a sign of drought tolerance), or winter wet in heavy UK clay soils (the combination of cold and persistent wet in winter is the most common cause of celmisia loss in UK gardens; the plants are hardy to frost but are killed by sustained cold and wet combined). Celmisia is a genus of around 60 species of rosette-forming or cushion-forming, evergreen, daisy-family perennials and subshrubs from alpine and subalpine habitats in New Zealand and south-eastern Australia; they are grown in UK gardens for their attractive, often silvery-grey or white-felted foliage and their white, yellow-centred, daisy flowers produced on upright stems from May to July. The foliage is the principal ornamental quality of most species: many celmisias have narrow, strap-like or lance-shaped leaves with a striking silver or white felted coating on the undersides or on both surfaces; this covering (tomentum) consists of fine hairs that reflect intense alpine sunlight and reduce moisture loss in the dry, windy, high-altitude grassland conditions from which the plants come.

Q: Is celmisia hardy in the UK?

Celmisia hardiness in the UK is a nuanced topic; the most commonly grown species (Celmisia spectabilis, C. semicordata, C. hookeri, and others) are genuinely cold-hardy, tolerating air temperatures to -15°C or below, but they are notoriously difficult to keep alive in UK gardens over multiple years because the limiting factor is almost never absolute cold but rather the combination of cold and wet in UK winters. The plants come from habitats where winters are cold and dry or cold and snowy (snow is dry and insulating); they are poorly adapted to the sustained cold, grey, wet UK winter that is the norm in much of lowland England. In rock gardens or raised beds with perfectly draining, gritty or scree-mix growing media in an open, south-facing, sunny position, celmisia can be reliably perennial in the UK; in ordinary border soil in a typical UK garden, they usually die within two to three winters regardless of their cold-hardiness rating. The alpine or scree house (an unheated but dry, well-ventilated structure) is the traditional UK solution for growing the more demanding celmisia species; in this environment they receive plenty of winter light and remain dry at the root while the air temperature matches the outdoor winter.

Q: How do I grow celmisia in the UK?

Celmisia is best grown in a rock garden, raised scree bed, or an alpine house in the UK; the essential requirements are maximum sun, perfect drainage, and dry winter conditions. A growing medium of one part loam, one part grit, and one part horticultural grit or crushed stone provides the freely draining, low-fertility conditions the plants require; do not add compost or fertiliser, as rich conditions produce lush, soft growth that is more susceptible to rot. Plant in a south or south-west facing position to maximise light and minimise winter wet; an open position with good air circulation discourages the fungal conditions that cause crown rot. Apply a deep grit or gravel mulch (5 to 10 cm) around each plant, keeping it clear of the leaf bases, to reduce moisture sitting at the crown. Water from above is particularly damaging to celmisia; direct watering onto the silvery-felted leaves can mat the hairs and provide entry points for fungal rot. Water only at the base in dry weather and avoid overhead watering entirely. An alpine house or cold frame provides ideal winter conditions: the plants remain dry, receive full winter light, and experience air temperatures close to the outdoor minimum. In a cold frame, keep the lights (covers) on through wet weather in winter while providing ventilation on dry days.

Q: Why do celmisia leaves go grey or silver?

The grey or silver colour of celmisia leaves is a natural characteristic produced by a dense covering of fine, white or silvery hairs (tomentum) on one or both surfaces of the leaves; this is not a symptom of disease or stress but an inherent feature of most species and one of their principal ornamental qualities. The tomentum is an adaptation to the intense ultraviolet radiation and high wind that characterise the alpine and subalpine grassland, cliff, and rocky slope habitats where celmisia grows in New Zealand; the white hairs reflect excess radiation and create a boundary layer of still air at the leaf surface that reduces moisture loss in the dry, windy conditions. The degree of silvering varies between species: Celmisia semicordata has exceptionally striking, broad, silver-white leaves; C. spectabilis has narrower leaves with a whiter upper and lower surface; C. hookeri is stiffer with a narrower, more green-grey leaf. New growth is often the most intensely silver; older leaves at the base of the rosette can become greener or more matte over time. If celmisia leaves that were previously silver become green, limp, and soft, this is likely a sign of excessive water or nitrogen rather than a natural ageing process; reduce watering and do not feed.

Celmisia (New Zealand daisy) is a genus of silver-leaved, alpine, rosette-forming perennials and subshrubs grown in UK rock gardens for their striking silver-grey or white-felted foliage and white daisy flowers. The silvery leaf colour is natural and ornamental; the plants are cold-hardy but notoriously difficult to overwinter in wet UK conditions. Perfect drainage in an open, sunny position is non-negotiable.

Waterlogging

Waterlogging is the most common cause of celmisia failure in UK gardens; the roots rot rapidly in saturated, poorly aerated soil, causing the silver-grey leaves to curl, yellow at the base, and eventually collapse. The plants come from well-drained, rocky alpine grassland where water passes quickly through the substrate; even brief periods of waterlogging are damaging, and sustained wet conditions in winter are almost invariably fatal. Heavy UK clay soils and low-lying, poorly draining garden positions are the most lethal environments.

What to do

Plant only in freely draining conditions; a rock garden, raised bed, or scree bed with a growing medium of equal parts loam, grit, and crushed stone is ideal. Avoid heavy clay or compacted soil entirely; if the garden soil is heavy, grow celmisia in a dedicated raised bed or container with a gritty, free-draining mix. Apply a deep grit collar around each plant to keep the crown dry; a cold frame or alpine house provides ideal conditions through UK winters.

Crown rot

Crown rot (fungal rot at the base of the rosette where the densely felted leaves meet the roots) is the most direct cause of sudden celmisia collapse in wet UK conditions; the fine hairs of the tomentum can trap and hold moisture, creating ideal conditions for fungal pathogens at the crown. Water directed onto the leaves from above exacerbates the problem; rainfall sitting in the centre of the rosette in cool conditions causes rot to establish rapidly.

What to do

Never water celmisia from above; water only at the base in dry conditions. Apply a collar of coarse grit (at least 5 cm deep) around the base of each plant to prevent moisture from sitting at the crown. Remove any dead or brown leaves from within the rosette promptly; decaying leaf material traps moisture and provides entry points for fungal pathogens. In wet periods, a pane of glass or polycarbonate propped over the plant on the windward side reduces rain penetration while maintaining air circulation.

Drought stress

Although celmisia requires perfectly draining conditions, it is not drought-tolerant in the sense of enduring sustained summer dryness; the silvery leaves curl inward along their length when the root zone dries out excessively in hot, dry UK summers, particularly in containers or very shallow, sandy soils. The silvery tomentum reduces water loss but the plants are from habitats with significant summer moisture from mist, cloud, and intermittent rainfall; complete drought causes progressive leaf curl and browning at the tips.

What to do

Water at the base (never overhead) during dry spells in summer; allow the growing medium to approach dryness between waterings but do not allow to dry out completely. A grit mulch retains some moisture at the soil surface while maintaining drainage and air circulation. Container-grown plants dry out most rapidly; check moisture levels regularly in hot weather.

Frequently asked questions

Why are my celmisia leaves curling?

Celmisia leaves curl most commonly because of waterlogging (roots rot in saturated soil; perfect drainage is essential; raised bed or rock garden required), crown rot in wet conditions (moisture sitting at the felted crown causes rapid fungal rot; never water from above; apply a deep grit collar), or drought stress in containers or very dry conditions (water at the base during dry spells; grit mulch helps). Cold and wet combined in winter is the most reliably lethal UK condition.

Is celmisia hardy in the UK?

Most commonly grown species (C. spectabilis, C. semicordata) are cold-hardy to -15°C or below but are notoriously difficult to keep alive in UK winters because the limiting factor is not cold but cold combined with wet. In a rock garden with scree-mix soil and a grit crown collar, or in an alpine house or cold frame, they can be reliably perennial. In ordinary border soil in a wet UK winter they typically die within two to three years.

How do I grow celmisia in the UK?

Grow in full sun in a rock garden, raised scree bed, or alpine house in a gritty growing medium (equal parts loam, grit, crushed stone); no compost or fertiliser. Apply a deep grit collar around the base; never water from above. An alpine house or cold frame (dry and ventilated) provides the best UK winter conditions. Remove dead leaves from the rosette promptly to prevent crown rot.

Why do celmisia leaves go grey or silver?

The silver or grey colour is natural: a dense covering of fine white hairs (tomentum) reflects alpine UV and reduces moisture loss in the windy, dry grassland habitats of New Zealand. This is not disease or stress. If leaves that were previously silver become green, limp, and soft, reduce watering and stop feeding; excessive moisture or nitrogen causes soft, green growth. New leaves are typically the most intensely silver; older basal leaves may gradually become greener.