Only one genus of Blechnum is nativ to Europe (Blechnum spicant). World-wide are ca. 200 species listet. A few of them are trunk-forming with age. The species B. brasiliense, B. discolor und B. gibbum are some of this trunk-forming species. Blechnum species are terrestrial ferns with leaves that are reddish when young but turn green with age. The genus usually can be recognized by the pinnatifid or pinnate fronds, with long sori running parallel to and on both sides of the costae. Some species are extreme dimorph. Fertile fronds are often longer stalked and have narrower pinnae than the sterile ones. Trunk-forming species are nativ to South-America, Asia, Africa and Australia. Most of them favor acidic soils. Spores are often difficult to germinate.

Cyathea is a very large genus with 500 - 600 species. The exact number of species is unknown. Cyathea comprises mostly terrestrial tree ferns. I think best known species is Cyathea cooperi. Most species of Cyathea are native to South- and Central America. Australia, but also present on many islands of the Pacific Ocean, including New Caledonia and Lord Howe Island.

The genus Caythea was divided into 3 groups of species. These have been called the Alsophila clade, the Sphaeropteris clade, and the Cyathea clade.

Fronds of Cyathea are up to tri-pinnate. Some of the species have sori without indusia, some with cup-shaped indusia and some with hooded indusia. Some species, for instance C. dealbata show a silvery underside on the fronds. New fronds are densely covered with many hairlike scales.