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Topic: silver fern

Is part of topic Common New Zealand ferns

ponga
Cyathea dealbata

Recognition: tree fern whose fronds have white undersides.  The stalks of the fronds can have a white bloom, allowing identification at a distance.

Distribution/ecology: only found in New Zealand.  In lowland to mid-altitude forest throughout the North Island and northern South Island, occurring sporadically south along the east coast as far as Otago.  Most common in drier, warmer, lighter forest.

Relationships: very closely related species occur in Australia and some Pacific Islands, but the white undersides of the fronds means silver fern is easily distinguished from the other tree ferns indigenous to mainland New Zealand. 

There are five indigenous species of Cyathea in mainland New Zealand, and another two on the Kermadec Islands.  There are some 500 species worldwide.  Some fern taxonomists divide the genus into segregates in which case the New Zealand species are treated in Alsophila and Sphaeropteris.

The scales on the fronds (and also easily seen within the crown) of Cyathea species easily distinguish them from the other group of tree ferns in New Zealand, Dicksonia, which are hairy.

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