Alsophila tricolor is the correct name for Cyathea dealbata in Alsophila because the epithet 'dealbata' is preoccupied by Alsophila dealbata C.Presl (now a synonym of Sphaeropteris glauca).
As well as being one of the most distinctive of the New Zealand tree ferns it is also most easily recognised. The silvery-white undersides of its fronds serve to immediately identify it. Its trunk is up to 10 m tall and about 45 cm in diameter at the base. It is fibrous with matted aerial roots and the upper part is marked by the bases of the old frond bases. It has numerous fronds that usually spread more or less horizontally. The rather slender stipes are covered with a silvery-white, waxy bloom. Its fronds are 2-4 m long by 60 cm to 1.2 m wide with deep green upper surfaces and they are three-times pinnate. The old fronds soon fall to leave a clean trunk. On very young plants the undersurfaces of the fronds are usually green because they do not develop their distinctive silvery-white colour until they are several years old. An alternative name is ponga, which is also a generic vernacular name for tree ferns in general. The Maori name of ponga has become corrupted into ‘punga’ and, sometimes ‘bungie’.
The silver tree fern is common in lowland to montane forests throughout the North and South Islands to about as far as the Catlins area on the east. It also occurs on the Three Kings and Chatham Islands. It has been introduced to Britain and Ireland and is now naturalised in Ireland.
