PL. —Dicksonia antarcticaBotanical illustration — drop image
Dicksonia antarctica

Tasmanian Tree Fern

SpringSummerFallWinter
8a10bHardiness zone
Background

Dicksonia antarctica is a tree fern native to eastern Australia, ranging from southeast Queensland to Tasmania. It develops a thick fibrous trunk over many decades and carries arching fronds that can span 3 meters across, making it one of the most structurally imposing plants for sheltered shade gardens.

The trunk is not true wood but a dense column of fibrous roots and accumulated stem bases. Growth is slow — typically 2–5 cm of trunk height per year — so large specimens are proportionally valuable and transplant well if kept moist in transit. The plant thrives in sheltered, humid positions with dappled to deep shade; strong winds shred the fronds. Water the crown and trunk as well as the root zone, since the fibrous trunk itself absorbs and holds moisture. Mulch heavily around the base to retain soil moisture and moderate temperature. In zones 8a–8b, pack the crown loosely with straw and wrap with horticultural fleece before hard frosts; established trunks offer some insulation to the growing tip. Prefers slightly acidic, humus-rich soil with reliable drainage.

The starchy pith at the centre of the trunk was consumed by Aboriginal Australians and used as a food source during periods of scarcity.

Care guide
SunPart shade to full shade
WaterConsistent moisture
SoilMoist, well-drained, humus-rich, acidic
Spacing8–12 ft
Height10–20 ft
Zone8a – 10b
Seasonal tasks
winter
watchDuring winter warm spells, briefly remove fleece from the crown to allow air circulation and reduce risk of crown rot.
spring
cutRemove brown or dead fronds from the previous season by cutting cleanly at the base close to the trunk without damaging the crown.
watchAs croziers begin to unfurl, water the crown daily during dry spells to support frond expansion.
sowPlant container-grown specimens in a sheltered, shaded position after all frost risk has passed.
summer
watchWater the trunk and crown thoroughly during hot or dry spells; the fibrous trunk must not dry out between waterings.
watchInspect fronds for scale insects and foliar nematode symptoms — brown, water-soaked lesions running between veins.
fall
cutCut away fronds damaged by wind or early cold to keep the crown tidy before winter.
watchIn zones 8a–8b, loosely pack the crown with straw and wrap with horticultural fleece before the first hard frost.
Common problems

Foliar Nematode

Symptoms

Brown, water-soaked lesions bounded by veins on fronds, spreading progressively from the crown upward. Affected tissue dries to tan or dark brown. Damage can resemble drought or scorch but follows vein boundaries distinctly.

Treatment

Remove and destroy affected fronds immediately; do not compost. Avoid overhead irrigation, which spreads nematodes through water films on foliage. No curative chemical option is practical in home gardens. Improve air circulation and keep foliage dry. Severely infested clumps should be dug and discarded.

Root rot

Symptoms

Plants wilt, yellow, and stunt even in moist soil; lower stems and roots turn brown, soft, and mushy and the plant may collapse. Most common in heavy, wet, or poorly drained ground.

Treatment

Improve drainage and stop overwatering, and never plant too deep. Lift and destroy badly affected plants along with the soil around the roots. Grow in raised or free-draining beds to prevent it returning.

Crown Rot

Symptoms

Lower leaves yellow and wilt; the base of the rosette turns brown and soft, sometimes with white fungal threads at the soil line. Plants collapse in wet conditions.

Treatment

Remove and destroy affected plants. Improve drainage and avoid overhead watering. Do not mulch directly against the crown. Space plants for airflow and avoid replanting in the same wet spot.