Austroblechnum colensoi, which is also known as Blechnum colensoi and commonly as as Colenso's Hard Fern, the Waterfall Fern, Peretao or Petako is a species of fern which is endemic to Aotearoa New Zealand. It is found throughout the North, South and Stewart Islands.
Austroblechnum colensoi is usually found in dark areas with good access to water, such as steep banks, river gorges and rocky overhangs.
Peretao has a stout, erect stem with dissimilar sterile and fertile fronds (dimorphic). The elliptic sterile fronds are dark-blue green and leathery, undivided or divided once into a small number of broad leaflets. Fertile fronds are extremely slender with long terminal leaflets.
ETYMOLOGY
colensoi: Named after William Colenso (7 November 1811 - 10 February 1899) who was a Cornish Christian missionary to New Zealand, and also a printer, botanist, explorer and politician.
BLECHNUM
Blechnum is one of the biggest fern genera in New Zealand, with 18 indigenous species. They are easily recognised because almost all have dimorphic (different looking) fertile and sterile fronds. The fertile fronds, which make the spores , have much thinner segments and are black or nearly so. They are also often held up above the sterile fronds.