Coprosmas (one of the largest genera of plants found in New Zealand) are related to the coffee plant. They are mostly shrubby, but eight species grow into small trees. Coprosmas frequently produce hybrids and are notoriously difficult to identify, so only some of the more common and easily recognised species are described here.
Leaves, flowers and berries
They all have leaves that come from the stem in opposite pairs, with small pits along the veins on the undersurface. Insignificant thread-like flowers are followed by masses of showy berries of many colours: translucent whites and blues, yellow, orange and red. These are sought-after by native birds.
Karamū (Coprosma robusta) grows throughout the two main islands on open sites in coastal and lowland–montane forest and in scrub. It has spreading branches and leathery, dark green leaves up to 12 centimetres long and five centimetres wide, which can be recognised by their finely toothed margins. Like most other large-leaved coprosmas, karamū flowers in spring.
Kanano (C. grandifolia, previously C. australis) looks very similar to karamū, but has a slightly different distribution and habitat. It favours more moist and sheltered sites, where it is common in regenerating areas and along logging roads. In the eastern South Island, kanano is restricted to Marlborough, and is not found south of Lake Ianthe in the west. Kanono’s branches are more upright and its leaves are larger (15–20 centimetres long and 7–10 wide) and mottled yellow-green. Unlike karamū, kanano flowers in autumn.
Taupata (C. repens) is a coastal tree, growing throughout the North Island and the top half of the South Island. It has orange-red berries, pale bark and thick, glossy, almost succulent leaves. It is widely grown as a hedge plant.
Hūpiro – stinkwood
Stinkwood (C. foetidissima) is common in the forest understorey and in scrub, from the Coromandel southwards. It is most easily recognised by the rotten-egg smell released when its leaves are crushed. The leaves are a dull light green and oblong or egg-shaped.
Small-leaved shrubby coprosmas
There is a multitude of lookalike small-leaved divaricating shrubs that inhabit the understorey of forests and dominate shrubland throughout New Zealand, and about 30 of these are coprosmas. They are particularly common in Canterbury and Westland. Identifying them is difficult because of genetic and environmental differences within species. Even botanists are prone to calling any small-leaved divaricating forest shrub a coprosma, knowing they have a good chance of being right. Many species have yet to be formally named.
Leaves come in a variety of shapes – round, wedge-like, or narrow and linear – and can be thick or thin. Some small-leaved shrubby coprosmas have hairy branchlets. The fruit come in all colours, and this is one of the most distinguishable features. Anyone keen to identify these coprosmas needs a hand lens and an illustrated field guide.