Cyathea cooperi - Australian Tree Fern

Cyathea cooperi, also known as Cooper's Cyathea, is an impressive, fast-growing tree fern. This beautiful species, native to the humid forests of Queensland, Victoria in Australia, and Tasmania, is a frost-sensitive plant, more suited for container cultivation than for open ground in our latitudes. The elegant fern forms a slender and dark false trunk (stipe) and carries an opulent crown of large light green fronds that are as luxuriant as they are graceful. Creating an exotic decor on its own, it will find its place on a semi-shaded terrace throughout summer and will be a centrepiece for the conservatory in winter. Always place in diffused light. The cultivation of this wonderful plant requires a certain expertise.

Cyathea cooperi belongs to the Cyatheaceae family. It is a species of warm and humid temperate climate that only tolerates weak and brief frosts. The fronds will be "burned" at -3°C (26.6°F), and the trunk will not survive below -6°C (21.2°F). In nature, this fern finds a constant climate throughout the year, characterised by regular and heavy rainfall and a temperature that varies seasonally by only 10 to 18°C (50 to 64.4°F), 15 to 20°C (59 to 68°F), or 18 to 25°C (64.4 to 77°F). It grows in semi-shade, in leached acidic soils, which are cool, light, and poor in organic matter but rich enough in minerals.

The plant shows rapid growth of about 25 to 40cm (10 to 16in) per year, more in a warm temperate greenhouse. It develops a slender (10 to 15cm (4 to 6in) in diameter) and tall false trunk that can reach 5 to 6m (16 to 20ft) in height. This false trunk is made up of intertwined rhizomes covered with dry adventitious roots and the brown, scaly, and papery remnants of the petioles of the old fronds. The base of the fronds is also covered with brown scales, giving them a coarse fur-like appearance. The young coiled fronds, called croziers, are scaly, and unfold into large fronds measuring 2 to 3m (7 to 10ft) in length, finely dissected, ranging from bright green to light green in colour. They are produced at the top of the trunk, one after the other, without interruption if the plant is kept above 10°C (50°F). Each frond is traversed by a reddish-brown rachis. The fronds are evergreen and each has an average lifespan of 2 years when frosts are not too severe.

Tree ferns are not known for their great hardiness, and Cyathea cooperi is no exception. The best solution is to grow it in a large pot and bring it indoors during winter to a frost-free or minimally heated conservatory. In addition to its low cold resistance, this tree fern only thrives in the diffused and humid atmosphere of an understory and in a light, cool soil with no trace of limestone. Therefore, its cultivation in open ground is reserved for the most temperate areas.