Cyathea is the largest family of tree ferns, with 500+ species. The word Cyathea comes from the Greek kyatheion meaning ‘little cup’ referring to the sori found on the underside of fronds. The Cyathea genus of tree ferns includes the world’s tallest tree ferns, which can reach heights in excess of 20m. According to Large and Braggins (2004) fossils found in Tasmania can date the Cyatheaceae family to the late Jurassic period with the fossils of the modern genera of Cyathea uncovered in the USA dated to the Tertiary period.
As a generalisation Cyathea tree ferns tend to be faster growing than other types of tree fern. Typically the fastest growing tree ferns are the taller species with thinner trunks. Often these species are found in warm tropical climates. In these tropical areas growing conditions are ideal with warm relatively stable temperatures, consistent hours of sunlight, high humidity and rainfall. These conditions create highly competitive biomes of climax vegetation; encouraging plants to compete to get light in the upper canopy.
Cyathea cunninghamii also known as the Gully tree fern or Slender tree fern is an interesting example of species that has had to adapt to its habitat. Cyathea cunninghamii grows in gully’s with low light levels across Victoria, New South Wales, Queensland and Tasmania in Australia and the Chatham Island in New Zealand. The species can grow up to 20m in height, but unlike other species competing for light the species is slow growing due to the cool conditions and low light levels making photosynthesis more difficult.
Tree fern species growing in tropical conditions have adapted to have ‘fleshy’ delicate fronds allowing Chlorophyll to perform photosynthesis more efficiently. In tree fern species such as Dicksonia antarctica and fibrosa that can tolerate varying degrees of frosts the frond structure is lot coarser giving better protection to the membranes around the Chlorophyll. These species are often very slow growing as they have evolved in conditions not suited to year round growth offered in the nutrient rich ecosystems of tropical regions.
Another species that has had to adapt to its ecosystem is Cyathea tomentosissima, this fern is commonly referred to as the ‘Dwarf Wooly tree fern’. As the name suggests this tree fern doesn’t grow to the heights of species such as Cyathea cunninghamii, again this is due to the species adapting to the conditions of its native habitat in the cool mountain forests and exposed grasslands of New Guinea. These areas can experience intense sunlight and its dwarf habit offers it more protection from the sun light. The fronds are also coarser to the touch and covered in red/brown hairs again giving it more protection from sun light and frost.
As you can see there are always exceptions to the rule but generally speaking Cyathea species tend to be faster growing and taller than other types of tree fern. If you live in an area where frosts are infrequent and light or you can grow plants in a cool conservatory species such as Cyathea dealbata, Cyathea medullaris or Cyathea tomentosissima can really add something unique and beautiful to your garden.