Photo: No machine-readable author provided. Hans B.~commonswiki assumed (based on copyright claims)., Public domain · source
Fern · Dicksoniaceae
Soft tree fern
Dicksonia antarctica
In other languages: Boomvaren (Nederlands) · Fougère arborescente (Français)
The soft tree fern comes from the damp forests and gullies of south-eastern Australia and Tasmania. It forms a thick brown trunk covered in a dense mat of fibrous roots, topped by a crown of large, arching fronds 1.5–3 m long. The trunk grows only a few centimetres a year, so a plant a few metres tall is often several decades old. In the garden it gives an instant tropical, jungle-like look to a sheltered, shady corner. In Belgium it is only borderline hardy: the crown must be well wrapped in winter.
Caution: Not reliably hardy: without good winter protection it usually does not survive a hard Belgian winter. It has only one growing point, at the top of the crown; if that freezes, the whole plant dies.
Light
Partial shade or shade
tolerates little sun
Moisture
Normal to wet
must not dry out
Legal basis
Sand, loam or peat
acid to neutral
Hardiness
down to -8 °C
protect in harsh winters
Size
3 m
tall, 3 m wide
| Pruning months | April |
|---|---|
| Height | 3 m |
| Native to Belgium | No, planted |
| Poisonous to people and pets | Not known to be poisonous |
Identify
Soft tree fern: how do you recognise it?
- Habit
- Tree-like: a straight, unbranched trunk topped by a broad crown; in our gardens usually 1.5–3 m tall and up to 3 m across.
- Trunk
- Thick, soft and fibrous: a stem surrounded by a thick mat of roots, through which the plant also takes up water.
- Fronds
- Two to three times divided, 1.5–3 m long, dark green and slightly rough, in a rosette at the top of the trunk.
- Fiddleheads
- In spring new fiddleheads covered with brown hairs unfurl from the heart of the crown.
- Growth
- Slow: the trunk gains only a few centimetres a year.
- Spores
- Spore clusters on the edges of the leaflets of older fronds; ferns do not flower.
Plants: April–May · Pruning: April
In your garden
Why grow it?
- A spectacular focal point with a truly tropical look, for a shady garden or courtyard.
- In spring the new fiddleheads unfurl from the crown: a show that lasts for weeks.
- You buy it with a trunk of the height you want, so it looks mature straight away.
- In mild winters the fronds stay green and the crown looks good all year.
- Also grows in a large pot on a sheltered, shady terrace.
Soft tree fern: where does it grow best?
- Partial to full shade; in full sun the fronds soon dry out.
- Humus-rich, moisture-retentive soil: sand, loam or peat, acid to neutral, rich in leaf mould.
- Moist to wet, but draining: no standing water around the base of the trunk in winter.
- A spot sheltered from wind, for example between tall shrubs or in a courtyard: wind damages and dries the large fronds.
- Allow 2.5–3 m for the crown; humid air near a pond or under tall trees is a bonus.
- Light
- Partial shade and shade
- Soil type
- Sand, loam or peat
- Acidity
- Acid or neutral
- Moisture
- Normal or wet
- Size
- 3 m tall, 3 m wide
- Hardiness
- Half hardy (to -8 °C): protect it in harsh winters
Goes well with
- Hosta: Large leaves at the foot of the trunk, in the same moist shade.
- Japanese forest grass: Fine, cascading grass as low underplanting.
- Smaller ferns: Ferns at the base complete the jungle look.
- Hydrangea: Flowers in summer in the same sheltered partial shade.
Maintenance
Soft tree fern: when and how to plant it?
Plant in April–May.
- Plant in April–May, once the soil has warmed up: this gives it a whole summer to root before its first winter.
- Dig a hole well wider than the trunk and mix plenty of leaf mould into the soil.
- Set the trunk deep enough to stand firm, about 20–30 cm for a 1 m trunk; stake taller trunks for the first few years.
- Backfill, firm well and water generously over the soil and over the top of the trunk.
- Spread a thick layer of leaf mould or mulch around the base.
- For the first few months water the trunk regularly, every day in warm, dry weather.
Care
- Water
- In dry spells pour water over the top of the trunk so it runs down: the trunk soaks it up. Daily in warm summers, preferably with rainwater.
- Feeding
- From May to August, occasionally give a diluted organic liquid feed at the base and over the trunk.
- Mulching
- A thick layer of leaf mould around the base keeps the soil cool and moist.
- In a pot
- A large, heavy pot with humus-rich, free-draining potting compost; water over the trunk in a pot too.
- Old fronds
- Cut off brown, dead fronds leaving a stub on the trunk, so the trunk is not damaged.
Tip: In dry spells pour water over the top of the trunk, because that is where the roots that take up water are. In November stuff straw into the heart and wrap the crown in fleece: below −8 °C it dies.
Soft tree fern: when to prune it?
Pruning months: April.
When: In April–May, once the winter protection is off and frost is over. Only remove dead fronds.
How:
- Cut off brown, dead fronds, leaving a stub of a few centimetres on the trunk.
- Leave green fronds, even if slightly damaged: the plant needs them to grow.
- Only remove the protection when no more hard frost is expected.
Caution: Never cut into the heart of the crown: that is where the plant’s only growing point sits.
Propagation
- Spores
- The usual method: collect ripe spores in summer and sow them under glass on sterile, moist seed compost. It takes years to get a plant with a trunk.
- Offsets
- Older trunks sometimes produce small offsets at the base or on the trunk; these can be carefully detached and potted up.
Soft tree fern: how does it get through the winter?
Hardy to −8 °C: protect in harsh winters.
- Borderline hardy: below about −8 °C the plant dies, and the crown is even more sensitive than the trunk.
- Wrap the crown from November: stuff straw or dry leaves into the heart, fold the old fronds up over the crown and wrap everything in horticultural fleece.
- In severe frost wrap the trunk too, with fleece, hessian or straw, and remove the protection again in April.
- In a pot: move it for the winter to a cool, light, frost-free place and water sparingly.
Diseases and pests
- Brown fronds: Dried-out, brown fronds in summer: too little water on the trunk, too much sun or wind. Water the trunk regularly and choose a more sheltered spot.
- Frost damage: Black, limp fiddleheads in spring: the crown has frozen. Wrap the crown better in future; if the heart is dead, the plant will not recover.
- No new fronds: After winter no new fronds appear yet: wait until June, as some plants are late. If the heart then stays brown and soft, the plant is dead.
Through the year
- January: Check the protection, especially after storms or snow.
- March: Leave the protection on until hard frosts are over.
- April: Remove the protection. Cut off dead fronds. Plant.
- May: Plant. New fiddleheads unfurl. Water over the trunk.
- June: Water over the trunk in dry spells. Feed now and then.
- July: Water over the trunk daily in warm weather.
- August: Water over the trunk in dry spells. Last feed.
- September: Water less.
- October: Bring potted plants inside before the first frost.
- November: Wrap the crown with straw and fleece.
- December: In severe frost, wrap the trunk too.
You and this species
Did you know?
- The trunk is not wood: it is a stem surrounded by a thick layer of roots, which take up water and nutrients.
- Many trunks on sale come from Tasmania, where they are salvaged from land due to be logged; they are shipped without roots and root again in the garden.
- A two-metre trunk is easily several decades old.