(Parablechnum tuerckheimii)
Blechnum (hard fern) is a genus of between 150-220 species of ferns with a cosmopolitan distribution, in the family Blechnaceae in the eupolypods II clade of the order Polypodiales.By far the greatest species diversity is in tropical regions of the Southern Hemisphere, with only a few species reaching cool temperate latitudes in the Southern Hemisphere (notably B. penna-marina, south to Cape Horn, Chile, the southernmost fern in the world) and Northern Hemisphere (notably B. spicant, north to Iceland and northern Norway).Most are herbaceous plants, but a few species (e.g. B. buchtienii and B. schomburgkii in Ecuador) are tree ferns with stems up to 3 m tall. Blechnum varies from most ferns in having a separation of sterile (photosynthetic) and fertile (reproductive) fronds in the same plant.