Coprosma is a genus of flowering plants in the coffee family, Rubiaceae, comprising shrubs, subshrubs, and small trees. The genus was established in 1776 by Johann Reinhold Forster and Georg Forster from material collected during James Cook's voyages, and GBIF currently lists around 177 descendant taxa within it. Coprosmas are predominantly evergreen, with foliage that ranges from tiny scale-like leaves in divaricating shrubs to broad glossy blades in larger species.
The flowers are small, wind-pollinated, and have insignificant petals — a reflection of the genus's reliance on the breeze rather than insects for cross-fertilisation. Most species are dioecious, bearing male and female flowers on separate plants, though some New Zealand species occasionally produce perfect flowers as well. The fruit is a juicy, non-poisonous berry, and one of the genus's most distinctive horticultural features is the extraordinary range of berry colours: bright orange, red, blue, white, or even translucent and colourless.
The name itself is a botanical in-joke. Coprosma is derived from Greek roots meaning "smelling like dung," in reference to the methanethiol odour released by the crushed leaves of certain species — most famously the New Zealand stinkwood, Coprosma foetidissima. A second curiosity sits on the underside of many Coprosma leaves: domatia, tiny hollow cavities that house mutualistic mites which help control parasitic leaf fungi.
Coprosma is centred on the South Pacific. Species are native to New Zealand, Australia, New Guinea, Borneo, Java, the Hawaiian Islands, several other Pacific island groups, and even the remote Juan Fernández Islands off Chile. New Zealand is the heart of the genus's diversity, where Coprosma berries are an important food source for native birds and where the shrubs form a structural component of forest understorey and coastal scrub. Better-known members include Coprosma robusta and C. lucida (both called karamū), C. repens (taupata or mirror plant), and C. foetidissima (stinkwood). Several of these — particularly the variegated cultivars of C. repens — are widely grown ornamentally for their salt tolerance and lustrous foliage.
Etymology
The genus name Coprosma combines Greek roots meaning "dung" and "smell," literally "smelling like dung." It refers to the sulphurous methanethiol odour that the crushed leaves of several species release — a trait so pronounced in one New Zealand member that it earned the epithet foetidissima and the common name stinkwood. The genus was named by Johann Reinhold Forster and his son Georg Forster, naturalists on James Cook's second Pacific voyage, and published in their 1776 work Characteres Generum Plantarum.
Distribution
Coprosma has a broad Pacific and Australasian distribution. Native species occur in New Zealand, Australia, New Guinea, the Indonesian and Malesian region (Borneo, Java), the Hawaiian Islands, numerous smaller Pacific island groups, and the Juan Fernández Islands off the coast of Chile. New Zealand is the centre of diversity for the genus, with dozens of native species occupying habitats from coastal cliffs to alpine herbfields.
Ecology
Coprosmas play a notable ecological role through their fleshy berries, which are consumed and dispersed by birds across the genus's range. The genus is also known for leaf domatia — tiny pits or hollows on the underside of the leaves — that serve as shelters for predatory and fungivorous mites. These mites help suppress parasitic fungi on the leaf surface, an example of a plant–arthropod mutualism that is widespread but particularly conspicuous in Coprosma. The wind-pollinated, dioecious breeding system means populations rely on having both male and female plants nearby to set fruit.
Cultivation
Several Coprosma species are grown ornamentally, with Coprosma repens (mirror bush) by far the most widely cultivated. It is valued for its glossy, salt-tolerant foliage and is a staple of coastal plantings; numerous variegated cultivars such as 'Picturata', 'Evening Glow', 'Marble Chips', and 'Marble Queen' have been selected for foliage colour, and 'Marble Queen' and 'Picturata' received the RHS Award of Garden Merit in 2017. As a group, garden Coprosmas prefer moist, well-drained, neutral to slightly acid soils in full sun or light shade, tolerate maritime exposure well, and are generally hardy in the milder parts of temperate zones (broadly USDA zones 7–10, depending on species), though hardiness varies considerably and many species are intolerant of hard frost.
Propagation
Coprosmas are propagated from seed or cuttings. Seed germination is notoriously slow — often more than twelve months — so fresh seed sown into a cold frame gives the best results, with stored seed typically sown in spring. Mature current-year wood taken as cuttings in autumn and rooted in a frame is the standard vegetative method and is also how named cultivars are reliably reproduced.
Cultural uses
The berries of some Coprosma species are edible raw, and Māori children were historically reported to eat them. The roasted seeds of certain species have been used as a coffee substitute — fitting, given that Coprosma sits in the same family as coffee. The wood of some species yields a yellow dye that does not require a mordant.
Conservation
While the genus as a whole is not the subject of a single global conservation listing, individual species have notable status outside their native range. Coprosma repens, the popular mirror bush, has naturalised in coastal Australia where it is classified as an environmental weed, illustrating that this otherwise ornamental genus can become invasive when planted beyond its native Pacific range.
Taxonomy notes
Coprosma was published by J.R. Forster and G. Forster in Characteres Generum Plantarum (1776), and is currently treated as an accepted genus in the Rubiaceae (order Gentianales, class Magnoliopsida) on GBIF, which records 177 descendant taxa. The genus is overwhelmingly dioecious, but a few New Zealand species are reported to bear occasional perfect flowers, a feature of taxonomic interest within the family.
