Why Are My Dicksonia Fronds Curling?

Drought stress

Drought is the most common cause of dicksonia frond curl in UK gardens. The large, finely divided fronds transpire significant quantities of water and the plant requires regular moisture both at the root zone and directly into the crown, from which all new fronds emerge. In dry conditions the frond pinnules curl inward along their length, the frond tips curl downward and brown, and in severe drought the entire frond may curl and die before the end of the growing season. Unlike ground-level ferns, dicksonia also absorbs water through the fibrous trunk, which must remain moist for the plant to maintain healthy frond production. A dry trunk in a dry summer contributes significantly to frond stress.

What to do

• Water dicksonia generously in dry weather, directing water into the crown at the top of the trunk as well as at the base. The crown watering is particularly important: it delivers moisture directly to the growing point where new fronds emerge.
• Mist the fronds and trunk with a hose in hot, dry weather. Misting raises the local humidity around the plant and reduces frond transpiration, significantly reducing curl in heatwave conditions.
• Apply a thick mulch of bark or garden compost around the base of the trunk to retain soil moisture and keep the root zone cool.
• Plant dicksonia in a sheltered, humid microclimate: beside a water feature, in a courtyard garden, or under the canopy of taller trees that maintain higher air humidity and reduce soil moisture evaporation.

Frost damage

Frost is the most serious threat to dicksonia in UK gardens. Dicksonia antarctica is hardier than its exotic appearance suggests and can tolerate brief frosts to around minus 5 degrees Celsius when the crown is protected, but the crown (the growing point at the top of the trunk from which all fronds emerge) is frost-sensitive, and a hard frost that penetrates the crown can kill the plant entirely. Frost causes the current season's fronds to curl, blacken, and collapse, and if the frost is severe enough to penetrate the crown, no new fronds emerge the following spring. The fronds themselves are less important than the crown: a plant can lose all its fronds to frost and regenerate fully if the crown survives.

What to do

• Protect the crown before the first frosts of autumn by filling it with dry straw, bracken fronds, or loosely packed horticultural fleece. Tie the old fronds upward and inward around the growing point to create a natural tent of insulation, then fill the interior with dry insulating material.
• Wrap the trunk with horticultural fleece or hessian in areas where temperatures regularly drop below minus 5 degrees Celsius. The trunk itself contains the reserves the plant needs to regenerate fronds after frost, and protecting the trunk from the worst of the cold is important for the plant's long-term survival.
• In particularly cold or frost-prone areas, move potted dicksonia into a frost-free but cool and light greenhouse, conservatory, or polytunnel for the winter months. This is only practical for trunked specimens in large pots or containers.
• Remove the insulation and dead fronds in April or May when the risk of hard frost has definitively passed. New croziers should be visible at the crown if the plant has survived. Be patient: dicksonia sometimes takes until June to show signs of life after a hard winter.

Too much sun and wind

Dicksonia in its natural habitat grows in the sheltered, humid, dappled light of temperate rainforest understorey. In full, exposed sun or in a windy position, the large fronds curl inward and dry out, developing scorched patches and brown frond tips much faster than in a sheltered, shaded microclimate. Cold, drying winds in winter are particularly damaging: they desiccate the evergreen fronds and accelerate the damage from frost. The combination of wind, sun, and frost is the most common cause of dicksonia failure in UK gardens.

What to do

• Plant dicksonia in a sheltered, dappled-shade position: beside a south or west-facing wall that provides wind shelter and reflected warmth, under the canopy of large trees, or in a courtyard garden with good wind protection on all sides.
• Avoid planting dicksonia in open, exposed positions or in sites that funnel wind. Even in mild coastal areas, wind dessication of the fronds is a significant problem for exposed dicksonia.
• In windy positions, erect a temporary windbreak on the prevailing wind side of the dicksonia during winter. Hessian screens or purpose-built windbreak fabric are effective for small to medium-sized specimens.

Waterlogging

While dicksonia requires consistently moist conditions, it does not tolerate prolonged waterlogging. In persistently waterlogged soil the fibrous roots deteriorate and the base of the trunk can rot, causing the fronds to curl, yellow, and the plant to gradually decline. This is most likely in heavy clay soils that become saturated in winter and remain waterlogged for extended periods. A waterlogged dicksonia typically produces progressively smaller and more distorted fronds over one to two seasons before declining entirely.

What to do

• Plant dicksonia in well-drained soil or raise the planting position slightly to prevent water accumulating around the base of the trunk.
• Incorporate coarse grit and garden compost into heavy clay before planting to improve drainage.
• In containers, ensure that drainage holes are large and unobstructed, and that the container stands on feet to allow water to drain freely from the base.

Poor establishment

Dicksonia sold as bare trunks (without soil rootball) need a period of careful establishment before they produce healthy fronds. A newly planted trunk that has not yet developed a root system depends entirely on water absorbed through the trunk to support frond production, and the fronds of a poorly established trunk curl, brown, and die back rapidly in dry or windy conditions. This establishment period can take one to two full growing seasons, during which the plant needs consistent moisture and protection from extreme conditions.

What to do

• Water newly planted dicksonia trunks twice daily in dry weather through their first growing season, directing water into the crown and soaking the trunk regularly. The trunk must remain moist continuously for roots to develop.
• Plant newly acquired bare trunks immediately on receipt, or stand them in a bucket of water until planting is possible. Never allow a bare trunk to dry out completely before planting.
• Plant the base of the trunk 30 to 40 cm deep to provide stability and maximise the surface area of trunk in contact with moist soil, from which roots will emerge.
• In the establishment year, remove any fronds that die back to reduce moisture demand on the unrooted trunk, and allow the plant to focus its limited resources on root development.

Frequently asked questions

Why are my dicksonia fronds curling?

Dicksonia fronds curl most often from drought stress or frost damage. Dicksonia antarctica, the soft tree fern, is a moisture-demanding plant that requires regular watering both at the roots and directly into the crown, from which the new fronds emerge. Drought causes the fronds to curl and brown from the tips inward. Frost damages the tender croziers in the crown and the current season's fronds, causing them to curl, blacken, and collapse. In cold UK winters, protecting the crown with insulating material is the single most important action for overwintering dicksonia successfully.

How do I water dicksonia (tree fern)?

Dicksonia should be watered both into the crown (the top of the trunk where the fronds emerge) and at the base of the trunk. Watering the crown directly is particularly important as the fibrous trunk absorbs water and delivers it to the growing point where the new fronds develop. In dry weather, water the crown daily and the base of the trunk every two to three days. Dicksonia is also extremely responsive to misting: in hot, dry weather, misting the fronds and trunk with a hose significantly reduces frond curl and browning.

How do I protect dicksonia in winter?

Protect dicksonia in winter by filling the crown with dry straw, bracken, or loosely packed horticultural fleece before the first frosts. Tie the old fronds upward around the crown to create a protective tent around the growing point, then fill the interior with insulating material. Wrap the trunk with horticultural fleece or hessian in areas where severe frost is expected. The crown is the critical point to protect: if the crown survives, the plant will recover even if all the fronds are killed by frost. Remove the insulation and old fronds in spring when the risk of hard frost has passed.

How fast does dicksonia (tree fern) grow?

Dicksonia antarctica grows extremely slowly: approximately 2.5 cm of trunk per year in ideal conditions. This means a trunk of 1 metre represents roughly 40 years of growth. Most dicksonia sold in the UK garden trade are imported from Australia or Tasmania as felled trunks, which re-root when planted and resume growth from the crown. The fronds, however, grow relatively quickly each season: each new frond unfurls rapidly from the crown crozier in spring and summer. The slow trunk growth is why established dicksonia in a garden are genuinely valuable plants.