Dicksonia

The genus Dicksonia was first described in 1788 and consists of around twenty living species of tree ferns. The type specimen for the genus, Dicksonia arborescens, is from the island of Saint Helena.

Most species form a trunk, which may be ten meters (33 feet) or more in height, with a spreading crown of fronds measuring 180 - 240 cm (6 to 8 feet) in length. The width of the trunk varies from species to species, and may be slender or massive. Some species have a creeping habit and do not form a trunk. It is thought that some of the large, slower-growing species of Dicksonia may possibly live for 200 years or more.

As with Cibotium, Dicksonia have hairs rather than the scales found on Cyathea.

They are endemic to Central and South America, the Juan Fernández Islands, Saint Helena, Samoa, New Caledonia, Malaysia, Indonesia, the Philippines, New Guinea, eastern Australia, and New Zealand.

Worldwide distribution of Dicksonia species:

Dicksonia are a member of the Dicksoniaceae family (which also includes Calochlaena, Cibotium, Culcita, Cystodiopteris, and Thyrsopteris).

The fossilized remains of Dicksonia, including spore, have been found in rocks dating back to at least the Jurassic Period (145 to 200 million years ago), and the Dicksoniaceae family dates back to at least the Triassic Period (200 to 251 million years ago). Two extinct species, Dicksonia kendallii and Dicksonia mariopteris, are well known as fossils occuring in the Jurassic strata of Yorkshire, England (dated at around 172 million years old).

All extant species of Dicksonia from the Americas are protected by Appendix II of the CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) treaty. These species are: Dicksonia berteriana, Dicksonia externa, Dicksonia sellowiana, and Dicksonia stuebelii.

The 1997 IUCN Red List of Threatened Plants also lists two of these species (Dicksonia berteriana and Dicksonia externa) as vulnerable. Both are endemic to the Juan Fernández Islands.

Click here for Dicksonia in the the Encyclopedia of Life.