This article was published in The Fringe, August 2014
Of the 57 species of Coprosma in New Zealand, the commonest species in the Waitakeres nowadays is karamu. I say 'nowadays' because it is a plant that prefers open sites, bush edges or disturbed ground. When the Waitakeres were wall to wall forest, Coprosma robusta would not have been so prolific.
Rather more common then was Coprosma lucida or shining karamu and at first glance the two can be easily confused.
Unlike most Coprosma which are small leaved, twiggy, divaricating forms, Coprosma robusta and C. lucida both have large leaves about 10cm long and a branching pattern more like a normal tree. Luckily they can also be easily identified. Firstly, 'lucida' means 'shining' and certainly the leaf is glossier than that of Coprosma robusta which has a dull matt leaf. Shining karamu also has a distinctly protruding midrib on both the upper and lower surfaces of the leaf blade, while Coprosma robusta is comparatively flat on the upper surface with the midrib protruding only on the lower surface. Another distinction not visible to the naked eye is the presence of fine-toothed serrations along the edge of the Coprosma robusta leaf, whereas the C. lucida leaf is entire, i.e. without serrations. Rub the leaf edge along your tongue to feel the difference.
Both have orange-coloured fruit but the fruit of Coprosma robusta tend to be quite sharply pointed and generally produced in abundance all along the branch lengths, while Coprosma lucida has almost spherical fruit that appear translucent when ripe and tend to be in concentrated clusters. The flowers of both plants are the typically inconspicuous ones that all Coprosma have, with male flowers being dangling filaments, and the female flower consisting of two protruding stigma and not much in the way of petals or other flower parts. In fact the strange thing about Coprosma robusta , and perhaps the reason it is so fertile, is that the female flowers are apomictic and can produce fertile seeds without being pollinated by a male.
Coprosma robusta is used a lot in restoration projects to provide the second phase of forest regeneration after manuka. As it is a broadleaf with fleshy fruit, it attracts birds that will in turn bring fruit of other species to be dispersed within the restoration area adding to the biodiversity. Unfortunately, that can sometimes mean weeds as well as preferred native species.
Early botanists recognised the family affinities between the native Coprosma genus and that of the coffee plant Coffea robusta, and William Colenso named the native plant Coprosma coffaeoides because of the similarities. During the World Wars Coprosma robusta was used as a coffee substitute and if you look inside the fruit you will find two seeds rather like the shape of coffee beans. Collect them, remove their flesh, dry them, roast them, grind them, and savour the aromatic flavour which just may be rather like coffee.