This is a genus in the Southern Hemisphere containing about 160 species, mainly tropical and subtropical. In New Zealand over 20 species, ranging from shrubs to small trees and from ground plants to epiphytes, occur in many types of vegetation and in many localities.
The two most common species are P. crassifolium, karo, and P. tenuifolium, kohuhu. These two and some others are cultivated widely. Many cultivars of kohuhu have been separated out including ones with dark coloured and with variegated leaves. Karo grows along forest margins and streamsides from North Cape to Poverty Bay and in the Kermadec Islands, while kohuhu is found in coastal and lower montane forest in both islands except that to the west of the Main Divide. This species is particularly variable and some forms come close to P. colensoi which occurs in forest and scrub mainly at higher elevations. Some species are of local occurrence only. Thus P. dallii is only found in north-west Nelson, P. turneri only on the Waimarino Plateau and the mountains adjacent, and P. rigidum in the Tararua Range. There is a group of six species, all divaricating shrubs, some of which are common in subalpine vegetation. Generally an epiphyte of more northern forests, P. kirkii also occurs as a ground plant. The seed of most species is contained in a sticky fluid inside a capsule. Distinctive juvenile leaf forms are present in some species.
by Alec Lindsay Poole, M.SC., B.FOR.SC., F.R.S.N.Z., Director-General of Forests, Wellington.