It is not certain the exact number of species of tree ferns there are, but it may be closer to 600-700 species. Many species have become extinct in the last century as forest habitats have come under pressure from human intervention.
Location of species
Lophosoria (tropical America, 1 species)
Metaxya (tropical America, 1 species)
Sphaeropteris (tropical America, India, southeastern Asia to New Zealand, the Marquesas, and Pitcairn Island, about 120 species)
Alsophila (pantropic area, about 230 species)
Nephelea (tropical America, about 30 species)
Trichipteris (tropical America, about 90 species)
Cyathea (tropical America, about 110 species)
Cnemidaria (tropical America, about 40 species)
Dicksonia (tropics and southern subtropics in Malaysia, Australasia, America, Hawaii, St. Helena, about 25 species)
Cystodium (Malaysia, 1 species)
Thyrsopteris (Juan Fernandez, 1 species)
Culcita (tropical America, Azores, Malaysia, Australasia, about 7 species)
Cibotium (Southeast Asia, Malaysia, Hawaii, Central America, about 12 species)
The fronds of tree ferns are usually very large, and multiple-divided fronds. The young fronds of tree ferns emerge in coils that uncurl as they grow.
Unlike flowering plants, tree ferns do not form new woody tissue in their trunk as they grow. Rather, the trunk is supported by a fibrous mass of roots that expands as the tree fern grows.
Tree ferns have a lengthy fossil record stretching back to the Triassic Period (251 to 199.6 million years ago). Members of both Cyatheaceae and Dicksoniaceae appear to have been diverse and relatively common during the succeeding Jurassic Period (199.6 to 145.5 million years ago) and Cretaceous Period (145.5 to 65.5 million years ago). However, the modern genera only become evident during the early Cenozoic (65.5 to 2.6 million years ago). Thus, the tree ferns apparently were affected by the mass extinction event recorded across nearly all groups of organisms at the close of the Cretaceous Period, which opened ecological niches for another period of diversification.
A number of tree ferns have become quite rare as a result of overcollection by humans. The root mantle on the trunk has been a commercial source of “orchid bark,” a fibrous nonrotting substrate for cultivating orchids and other epiphytic plants. The trunks have been carved into tiki statues and other craft items typically sold to tourists in tropical resorts. The trunk cross sections also produce a beautiful pattern of light and dark tissues originating from the vascular system of the stem and the leaf traces. These have been used for making various handcrafted items, including plates. Finally, a number of species have been collected from the wild for cultivation in greenhouses and conservatories. Governments have responded to these conservation threats by listing most tree ferns under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which prohibits international commerce involving these plants without a special permit.
Tree Ferns in CFSS