Soft tree fern
Balantium antarcticum (more frequently known as Dicksonia antarctica) is probably the most well known of an ancient group of palm-like plants generally known as the tree ferns. Tree ferns, members of the fern order Cyatheales, are distributed in tropical and subtropical regions as understorey plants of moist, humid environments. They are also found in temperate rain forests of South Africa, Australia and New Zealand. The spores, fronds and stems of tree ferns can also make up substantial proportions of the fossil record in some parts of the world.
Balantium antarcticum is native to high-rainfall areas of south-eastern Australia, sometimes forming the dominant species. It is also widely planted in other parts of the world as an ornamental for its attractive crown of foliage, which may reach six metres in diameter. In Sri Lanka there is evidence Balantium antarcticum has formed a naturalised population in the wild, following the species' escape from a botanic garden.
The trunk of Balantium antarcticum, which may be up to fifteen metres tall, is formed of a narrow stem surrounded by dense root masses and the bases of fallen fronds. These roots and frond bases help support the tuft of living fronds. Although Balantium antarcticum plants shed their dying fronds from the canopy, other tree ferns, such as Dicksonia fibrosa, a New Zealand species, retain their fronds in the form of a skirt.
Tree ferns are slow growing. Estimates of height increase range from one centimetre to ten centimetres per year, with plants not reaching maturity until they are over twenty years old. Consequently, despite being the most common tree fern in Australia, wild collection for the horticultural trade, and habitat destruction, have both contributed to the decline of Balantium antarcticum in its native range since the late Victorian period.
Balantium antarcticum is an attractive, adaptable, easily grown garden plant that has gained notoriety in the United Kingdom for it semi hardiness. Although it will tolerate frost it will generally lose its fronds over winter, so protection of the crown is usually necessary. The benefit of frond loss is that new fronds appear in the spring. The opportunity to watch the beautiful croziers, covered in dense brown hairs, unfurl is a sight not to be missed and will add a taste of the rainforest to any garden.
Other horticultural uses of Balantium antarcticum include trunks as fencing or as a medium for the cultivation of epiphytes.
Further reading
Large MF and Braggins JE 2004. Tree ferns. Timber Press.
Ranil, R.H.G. et al. 2014. Naturalization of Dicksonia antarctica Labill. in Pidurutalagala Mountain Forest Reserve and adjacent Eucalyptus plantation in Sri Lanka. Bulletin of the National Museum of Nature and Science. Series B, Botany 40: 107-112.
Lisa Friend