Plant Type:
Tree Fern
Cyathea australis is a magnificent ornamental with a striking, architectural presence. Its thick, rough-textured trunk is crowned by a lush, spreading canopy of large, arching, deep green fronds. This creates a captivating, tropical aesthetic, perfect for rainforest-style gardens or shaded landscapes. Its robust stature and elegant foliage add a dramatic focal point, evoking a sense of ancient, primeval beauty.
Cold Hardiness:
Half-hardy
Cyathea australis demonstrates good winter hardiness for UK gardens, generally tolerating frosts down to -7 to -8°C for short periods. Some sources even suggest it can withstand temperatures as low as -10°C. While relatively hardy, winter protection of the crown with straw or horticultural fleece is highly recommended, especially in colder regions or during prolonged freezing spells, to safeguard the vulnerable growing point and fronds.
Eventual Height:
2.5-4m
In UK gardens, Cyathea australis typically reaches a mature height of 2.5 to 4 meters, though it can grow taller in very mild, sheltered locations. It’s considered a fast-growing tree fern compared to Dicksonia antarctica, with new fronds quickly reaching 2 meters or more. Its trunk, however, is slow-growing, increasing by around 2cm annually. Consistent moisture and feeding during the growing season promote its vigorous frond production.
Light requirements:
Partial shade
Water Requirements:
Regular when growing
In UK gardens, Cyathea australis needs consistently moist soil, especially during the growing season (spring and summer). Water regularly, ensuring the trunk remains damp, as it absorbs water directly. Avoid direct watering of the crown in winter to prevent rot. While it appreciates humidity, especially in dry spells, it dislikes waterlogging, so good drainage is crucial. Reduce watering in winter as growth slows.
Caring for this plant:
Spring & Summer: In spring and summer, Cyathea australis growth accelerates. Ensure consistently moist soil, watering regularly, especially during dry spells. Apply a diluted liquid fertilizer every few weeks to encourage healthy growth. Protect from strong winds and direct sunlight. Misting the fronds occasionally increases humidity. Check for pests like aphids or scale insects and address them promptly.
Autumn & Winter:As autumn approaches, reduce watering frequency, allowing the topsoil to dry slightly between waterings. Protect the crown by wrapping the trunk with horticultural fleece or straw before frosts arrive. Mulch around the base for added insulation. In exposed areas, consider a temporary shelter. Avoid fertilizing during the dormant season. For container plants, move them to a frost-free environment if possible.
