Blechnum is a genus of greenhouse and hardy evergreen ferns.
B.auriculatum, from South America grows between 1.5 and 2 feet. B.brasiliense, from Brazil is tree fern which reaches between two and three feet.
Greenhouse species should be potted in March or April in a shady position of the greenhouse. Use a compost of equal parts loam, leafmould, peat and sharp sand. Give them plenty of water during the spring and summer but only water moderately after October.
An example of a hardy species if B.penna marina, which grows to around six inches. While it is hardy and can grow outdoors, make sure to provide protection if you expect it to be exposed to severe weather.
When cultivating the hardy species, plant between October and April in a shady using a compost of two parts sandy peat and one part of loam and powered limestone.