Tree fern

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 (scaly tree ferns), Dicksoniaceae, Metaxyaceae, and Cibotiaceae. It is estimated that Cyatheales originated in the early Jurassic,^[1][2] 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,^[3] and Osmundales where the extinct Guaireaceae and some members of Osmundaceae also grew into trees. In addition there were the Psaroniaceae including Tietea in the Marattiales, which is the sister group to all the leptosporangiate ferns.^[4]

Other ferns which are also tree ferns, are Leptopteris and Todea in the family Osmundaceae, which can achieve short trunks under a metre tall. Osmunda regalis is sometimes considered a tree fern.^[5] Fern species with short trunks in the genera Blechnum, Cystodium and Sadleria from the order Polypodiales, and smaller members of Cyatheales like Calochlaena, Cnemedaria, Culcita (mountains only tree fern), Lophosoria and Thyrsopteris are also considered tree ferns. The species Ctenitis sloanei (The Florida Tree Fern) from Florida, Mexico, Bermuda and the Caribbean is sometimes called a tree fern.^[6][7][8][9]