The order Cyatheales, which includes most tree ferns, is a taxonomic order of the fern class, Polypodiopsida. No clear morphological features characterize all of the Cyatheales, but DNA sequence data indicate the order is monophyletic. Some species in the Cyatheales have tree-like growth forms from a vertical rhizome, others have shorter or horizontal expanding rhizomes.
Cyatheales
Dicksonia antarctica at Kew
Tree fern frond ("fiddlehead") by the Akatarawa River, New Zealand.
Transplanted Dicksonia antarctica tree ferns at Combe Martin Wildlife and Dinosaur Park, Devon, England
The tree ferns are arborescent (tree-like) ferns that grow with a trunk elevating the fronds above ground level, making them trees. Many extant tree ferns are members of the order Cyatheales, to which belong the families Cyatheaceae, Dicksoniaceae, Metaxyaceae, and Cibotiaceae. It is estimated that Cyatheales originated in the early Jurassic, and is the third group of ferns known to have given rise to tree-like forms. The others are the extinct Tempskya of uncertain position, and Osmundales where the extinct Guaireaceae and some members of Osmundaceae also grew into trees. In addition there were the Psaroniaceae and Tietea in the Marattiales, which is the sister group to most living ferns including Cyatheales.
A tree fern near Belles, Dominica
Alsophila sp. tree ferns overlooking a valley in Misamis Oriental, Philippines
Reconstruction of Tempskya, an extinct fern from the Cretaceous
Transplanted Dicksonia antarctica tree ferns at Combe Martin Wildlife and Dinosaur Park, North Devon, England