Dicksonia antarctica

A soft tree fern from southeastern Australian rainforests

Dicksonia antarctica is native from southeastern Queensland through New South Wales and Victoria to Tasmania. Its apparent trunk is an upright fern stem wrapped in old frond bases and a dense mantle of fibrous roots.

Wild plants grow in rainforest and wet eucalypt forest, especially in sheltered gullies and beside creeks. High rainfall, cool humid air and deep shade allow large fronds to spread beneath the tree canopy. Mosses and smaller ferns often take root in the damp, fibrous trunk.

How to care for Dicksonia antarctica

Filtered light for a broad tree-fern crown

Give the tree fern medium to strong filtered light near a large east or north window, or well back from intense south and west sun. Gentle morning sun is acceptable when the root zone is wet and the plant is acclimated. Hot direct sun burns the broad fronds and dries the fibrous trunk; deep shade produces long weak fronds and a sparse crown. Keep the whole crown below the light source, not tucked beneath a low shelf.

Water for both root ball and trunk

Keep the root ball evenly moist at all times. Water thoroughly as soon as the surface begins to dry. During warm active growth, also wet the fibrous trunk and crown so the roots covering the trunk remain hydrated, then allow fresh water to drain and provide airflow. Never let the trunk or root ball dry through. Cool, low-light conditions reduce demand, but the plant still needs moisture and must not sit in stale water. A large frond crown, warmth, sun and a small pot raise demand substantially.

A moisture-holding mix below the tree-fern crown

Use a deep, humus-rich fern mix that holds plenty of moisture without becoming muddy. A blend of quality potting substrate or coir, fine bark, leaf mould and perlite or pumice works well. What looks like a trunk is an upright rhizome wrapped in fibrous roots, so both the roots in the pot and the trunk surface need water and air. Keep the crown fully above the substrate and never bury more of the trunk during repotting. Rinse salts away because repeated watering and feeding can concentrate them in the fibres.

Cooler conditions for a living fibrous trunk

A cool-to-mild indoor range of 10–24 °C is preferable. Keep a container-grown specimen above roughly 5 °C and shield the crown from frost. Established plants tolerate lower temperatures when protected and freely drained. Heated rooms above 25 °C greatly increase water and humidity demand. Avoid icy glass, winter draughts and radiator currents that dry the trunk or one side of the crown.

Humidity through a broad frond canopy

Moderate to high humidity, around 55–75%, helps the fronds unfurl fully and reduces dry leaflets. Provide broad air exchange through the crown and around the damp trunk so moisture remains fresh. A humidifier is more effective than misting; if the trunk is wetted, do it as part of a thorough watering and let the fronds dry steadily afterwards. Avoid crowding the crown against a wall.

Dilute feeding for an expanding frond crown

Developing tree-fern fronds can be fed with balanced complete fertiliser at quarter strength. Space applications four to six weeks apart. Apply it through the moist potting mix and use plain water on the trunk between feeds. Continue lightly through winter only if warmth and light keep new fronds growing and the plant remains thirsty; a cool resting plant needs little or none. Strong fertiliser can burn the fine roots in the trunk fibres, so avoid concentrates and rinse regularly.

A heavier pot without covering the trunk

Repot when roots densely fill the container, the plant becomes unstable, water no longer penetrates evenly or the mix has broken down. Choose a heavy pot 4–8 cm wider and deep enough for the existing roots. The trunk and crown do not tolerate rough handling. Retain the undisturbed core of the root ball, remove only loose degraded mix and never cut the trunk to make it fit. Repot while the plant is growing but not during excessive heat, and restore full moisture immediately.

Crown and old fronds

Give the frond crown ample room; it needs no stake if the heavy pot and roots are stable. Avoid cutting the trunk or damaging the coiled new fronds in the centre. Remove only fully brown fronds by cutting their stalks near the trunk, leaving green fronds to feed future growth.

Protecting the crown and fronds

Avoid forcing a coiled new frond open. Rinse mature fronds gently, support the stalks during moves and avoid wiping the many fine leaflets.

When Dicksonia antarctica fronds or croziers fail

Old fronds brown after winter or frost

Existing fronds can be damaged while the protected crown survives. Wait until the weather settles, then remove only fully dead fronds and check the crown for firm curled croziers. Avoid assuming the trunk is dead from brown foliage alone. A black, loose or foul-smelling crown is much more serious.

Croziers begin to unfurl, then dry or stop

The crown or fibrous trunk may have dried during active growth, or late cold may have injured the tender flush. Check moisture through the root zone and trunk, shelter the crown from extremes and keep conditions steady. Avoid pulling open a stalled crozier. Soft black tissue strongly suggests rot and needs prompt attention.

Large fronds are shredded or bent

Wind and repeated contact easily tear the broad fern canopy. Mechanical splits are dry and stop at the damaged section; they do not spread between fronds. Move a container to a sheltered site and support it securely. Keep partly green fronds because they continue feeding the crown.

The crown becomes black, soft or hollow

Crown rot is urgent because all new fronds arise from this single growing point. Remove loose dead material without gouging healthy tissue, prevent cold water from sitting in a damaged winter crown and seek specialist treatment if firmness is being lost. A destroyed crown cannot simply reshoot from an ordinary side bud.

Each new flush is smaller than the last

Repeatedly small fronds can indicate that the large root system or moisture-holding fibrous trunk is drying, that the plant remains too dark, or that roots were restricted during establishment. Check those physical conditions first. Continued decline with a shrinking crown calls for a root and trunk inspection, not stronger feed.

Pet access to tree-fern fronds

The pet toxicity of Dicksonia antarctica is unknown. Keep loose frond pieces away from animals that chew greenery and prevent access to the crown. Contact a veterinarian after ingestion, especially if the animal develops digestive upset or unusual behaviour.

James Dickson and the “southern” tree fern

Dicksonia honours Scottish botanist and nurseryman James Dickson. Charles Louis L’Héritier established the genus near the end of the eighteenth century. Antarctica means southern here; it does not mean that the fern grows in Antarctica. Jacques Labillardière described the Australian species in 1806.