New Zealanders know the kowhais by the plentiful yellow flowers which they bear in the spring, and these are attractive to the tui and bellbird because of the honey they contain. Trees are planted widely in parks and gardens for these reasons. There are three New Zealand species, one of them with two varieties, which are dispersed in a variety of habitats throughout New Zealand and the Chatham Islands. Two of them, S. tetraptera and S. microphylla, are trees growing to heights of 30–40 ft, and the third, S. prostrata, is a prostrate bushy shrub growing in grassland and rocky places east of the South Island Main Divide. Of the two trees, S. tetraptera has the larger leaves – they are pinnate in all species – and is confined to the North Island, while S. microphylla has smaller leaves and occurs in both islands and the Chathams. Typical habitats for these trees are forest margins, streamsides, and open places in lowland and montane areas. They both show a great deal of variation and probably hybridise where they meet. S. microphylla also hybridises with S. prostrata.
The wood is heavy, dense and strong and, when available, has been used in the past for tools and machinery and some cabinet work. Logs of sufficient size for sawing up are now rare.
There are about 30 species of Sophora in temperate and subtropical regions in both hemispheres of the world. One in Hawaii, S. polymorpha, is very similar to the New Zealand trees.
by Alec Lindsay Poole, M.SC., B.FOR.SC., F.R.S.N.Z., Director-General of Forests, Wellington.