Soft Tree Fern
Dicksonia antarctica
The Soft Tree Fern (Dicksonia antarctica) is a remarkable tree fern species belonging to the family Dicksoniaceae, and is one of the most iconic and widely cultivated tree ferns in the world. Despite its species epithet 'antarctica,' it is native to Australia, not Antarctica — the name refers to its southerly distribution on the Australian continent.
• One of the most cold-hardy tree ferns, capable of tolerating brief frosts down to approximately −5 °C (23 °F)
• Can grow a massive, fibrous trunk up to 15 m (49 ft) tall in its native habitat, though typically 4–5 m (13–16 ft) in cultivation
• Crown produces a magnificent rosette of large, arching, dark green fronds that can reach 2–6 m (6.5–20 ft) in length
• The trunk is not true wood but a dense mass of fibrous aerial roots and persistent stipe bases, giving it a soft, spongy texture — hence the common name 'Soft Tree Fern'
• One of the longest-lived fern species, with individual plants estimated to live 200–300 years or more in the wild
Taxonomy
• Primarily found in cool temperate and subtropical rainforests, moist eucalypt forests, and sheltered gullies
• Grows from sea level to approximately 1,000 m (3,280 ft) elevation
• Tasmania represents the southernmost extent of its range, which inspired the species name 'antarctica'
The genus Dicksonia belongs to the order Cyatheales, an ancient lineage of tree ferns:
• Tree ferns first appeared in the fossil record during the Jurassic period (~200–145 million years ago)
• The family Dicksoniaceae diverged early in the evolution of tree ferns and is considered one of the more primitive families within Cyatheales
• Fossil evidence suggests that tree ferns were far more widespread during the Mesozoic era, with Dicksonia-like fossils found in regions where they no longer occur naturally
• The genus Dicksonia comprises approximately 20–25 species distributed across tropical and subtropical regions of the Americas, Southeast Asia, Oceania, and the Pacific Islands
Trunk:
• Erect, columnar trunk composed of a dense mass of adventitious roots and old stipe bases — not true secondary xylem wood
• Trunk diameter typically 30–60 cm (12–24 in), occasionally up to 1 m (3.3 ft) in very old specimens
• Surface is brown, rough, and fibrous, covered with persistent stipe bases and fine reddish-brown hairs
• The trunk can absorb and store significant quantities of water within its fibrous matrix, serving as a reservoir during dry periods
• New root growth occurs continuously from the trunk apex, gradually increasing trunk height
Crown:
• Terminal crown forms a broad, spreading rosette of large fronds
• Crown diameter can reach 3–6 m (10–20 ft) in mature specimens
• New fronds (croziers) emerge tightly coiled at the apex, unfurling over several weeks in a characteristic circinate vernation pattern
• The growing apex (apical meristem) is nestled within a protective mass of fine, silky hairs — damage to this growing point is usually fatal
Fronds:
• 2- to 3-pinnate, broadly triangular in outline
• Individual fronds 2–6 m (6.5–20 ft) long, among the largest of any fern species in cultivation
• Rachis (central stalk) is stout, green to brown, covered with fine brown hairs
• Pinnae (primary divisions) are lanceolate, deeply divided into numerous pinnules
• Ultimate pinnules are oblong, serrate-margined, approximately 5–10 mm long
• Upper surface is dark green and glossy; lower surface paler with fine hairs along the veins
Sori:
• Sori are borne on the underside of pinnules, near the margins of the ultimate segments
• Each sorus is covered by a distinctive two-lipped indusium — the outer lip formed by the reflexed leaf margin, the inner lip a true membranous indusium
• Spores are trilete, approximately 40–50 µm in diameter, released when mature
Roots:
• Adventitious roots emerge from the trunk, forming a dense, fibrous mantle
• These roots are highly efficient at absorbing moisture and nutrients from the surrounding soil and organic debris
• The root mantle also provides habitat for epiphytic plants, mosses, and invertebrates in the wild
Habitat:
• Cool temperate rainforests, wet sclerophyll forests, and sheltered gullies with reliable moisture
• Frequently found along stream banks, in ravines, and on south-facing slopes where humidity remains high
• Often grows as an understory component beneath a canopy of tall eucalypts or alongside other rainforest species
• In Tasmania, it can form extensive stands in pure fern gullies
Humidity & Water:
• Requires consistently moist soil and high atmospheric humidity
• The fibrous trunk acts as a water reservoir, allowing the plant to buffer against short dry periods
• In the wild, the trunk often supports a community of epiphytic mosses, lichens, and small ferns that benefit from the retained moisture
Reproduction:
• Reproduces exclusively by spores — no vegetative reproduction in the wild (unlike some other tree ferns)
• Spores are wind-dispersed and require moist, shaded conditions to germinate
• Germination produces a small, heart-shaped prothallus (gametophyte) that requires a film of water for fertilization
• Growth is extremely slow — a trunk may take 50–100 years to reach full height in natural conditions
• Young plants are highly vulnerable to desiccation and competition
Ecological Role:
• Provides critical microhabitat structure in forest ecosystems
• The fibrous trunk supports diverse communities of epiphytes, invertebrates, and fungi
• Fallen trunks create nurse logs that facilitate regeneration of other plant species
• Important food source for certain invertebrate larvae in native ecosystems
• In Tasmania, wild populations have been significantly impacted by historical logging for the horticultural trade — tree ferns were extensively harvested from the wild for garden planting throughout the 20th century
• Tasmania now has strict regulations protecting wild Dicksonia antarctica; harvesting from the wild requires permits and is heavily controlled
• In Victoria and New South Wales, some local populations are threatened by habitat loss due to land clearing, bushfires, and climate change
• The species is protected under various state-level conservation acts in Australia
• Commercial cultivation from nursery-grown stock has reduced pressure on wild populations, but illegal harvesting remains a concern
• Climate change poses a long-term threat, as rising temperatures and altered rainfall patterns may reduce the extent of suitable cool, moist habitat
Light:
• Prefers dappled shade to partial shade; mimics its natural understory habitat
• Can tolerate morning sun if roots and trunk are kept consistently moist
• Avoid hot, direct afternoon sun, which can scorch fronds
Soil:
• Requires moist, well-drained, humus-rich soil with a slightly acidic to neutral pH (5.5–7.0)
• Incorporate generous amounts of organic matter (leaf mold, composted bark) into the planting site
• Avoid heavy clay soils that become waterlogged
Watering:
• The most critical aspect of cultivation — consistent moisture is essential
• Water the crown (apex) regularly, as the plant absorbs significant moisture through its growing point
• In dry climates, water the trunk as well as the soil; the fibrous trunk can absorb and store water
• During hot summer months, daily watering of the crown may be necessary
• Mulch heavily around the base to retain soil moisture
Temperature:
• Hardy to approximately −5 °C (23 °F) for brief periods; one of the most cold-tolerant tree ferns
• Prolonged hard frosts (below −8 °C / 18 °F) can damage or kill the plant
• In colder regions, winter protection is essential: wrap the crown with horticultural fleece, straw, or bubble wrap, and insulate the trunk
• Optimal growing temperature range: 10–25 °C (50–77 °F)
Propagation:
• Commercially propagated from spores, which is a slow process (several years to produce a saleable plant)
• Some nurseries produce plants from 'pups' — basal offsets that occasionally emerge from the trunk
• Tissue culture is also used for large-scale commercial production
• Home propagation from spores is possible but requires patience and consistent conditions
Common Problems:
• Brown, crispy frond tips → insufficient humidity or inadequate watering of the crown
• Collapsed or wilting crown → frost damage to the apical meristem (often fatal)
• Scale insects and mealybugs can occasionally infest the trunk and fronds
• In very wet, poorly drained soils, trunk rot can occur
Fun Fact
The Soft Tree Fern has a fascinating relationship with human history and horticulture: • In the Victorian era (19th century), tree ferns became enormously fashionable in British gardens, sparking a craze known as 'pteridomania' — an obsession with collecting and cultivating ferns. Dicksonia antarctica was among the most prized specimens, and thousands were harvested from Tasmanian forests and shipped to England in specially designed Wardian cases (early terrariums). • The fibrous trunk of Dicksonia antarctica has been used by Indigenous Australians for various purposes, including as a source of water in emergencies — squeezing the moist trunk fibers can yield drinkable water. • In modern horticulture, the trunk is sometimes cut from a mature plant and replanted — remarkably, if kept moist, a severed trunk can regenerate roots and produce new fronds, essentially growing a new plant. This technique has been used to rescue tree ferns from development sites. • A single large Dicksonia antarctica can produce millions of spores per year, yet the journey from spore to mature tree fern may take over a century in the wild — making each ancient specimen a living monument to centuries of patient growth. • The species has become a signature plant of the 'Temperate House' at Kew Gardens in London, where specimens planted in the 1840s and 1850s during the height of pteridomania still thrive today, their trunks now over 4 m (13 ft) tall — living witnesses to the Victorian fern craze.
Learn more
