Coprosma is a genus containing about 90 species, half of them occurring in New Zealand. Of these, all are endemic except one which is also found in Australia and Tasmania.
The remaining species occur principally in Hawaii, with some in Australia and Tasmania, Borneo, Java, New Guinea, and islands of the Pacific.
The family to which Coprosma belongs, the Rubiaceae, is a large, almost cosmopolitan one with over 5,000 species. It contains the commercial coffee tree.
The New Zealand species range from small trees to dwarf matted plants. They have opposite leaves with marked stipules joining each pair. On the under-surfaces of the leaves are little pits, or domatia, between the midrib and main veins. The bark contains dyes. Male and female flowers which are small and arranged in fascicles, are mostly borne on separate plants. The fruit is round and succulent and contains two or four seeds. It is of many different colours, ranging from translucent white to black. Some species have more than one coloured fruit.
The largest growing species is C. arborea, mamangi, which is a small tree 15–25 ft high common in open, lowland forest from near the north to about the centre of the North Island. C. grandifolia grows to 20 ft high and is common in forest up to the lower montane level throughout the North Island and the northern part of the South Island. The commonest species of all are C. lucida, karamu, and C. robusta, also known as karamu. The latter occurs particularly on alluvial soils in open forest and in shrubland.
C. repens or taupata is a prostrate or upright shrub growing within the influence of salt spray around the shores of the North Island and the Kermadec and Three Kings Islands. It is a very common hedge plant and has been introduced into overseas countries for this purpose. C. pumila and C. petriei form prostrate matted plants in montane to alpine vegetation.
by Alec Lindsay Poole, M.SC., B.FOR.SC., F.R.S.N.Z., Director-General of Forests, Wellington.