Coprosma robusta
Written by Craig Kelly (Lincoln University)
July 2005
Edited by Michael Hudson, Lincoln University, September 2006
Taxonomy
- Scientific name: Coprosma robusta
- Popular Common names: Karamu, glossy karamu
- Kingdom: Plantae
- Phylum: Magnoliophyta (Angiosperms, flowering plants)
- Class: Magnoliopsida (Dicotyledons)
- Order: Gentianales
- Family: Rubiaceae (the coffee family)
- New Zealand Status: native (endemic)
- Taxonomy sources: New Zealand Plant Conservation Network (2005), National plant database USDA (2003).
Identification
Species Description
The dioeciously evergreen karamu can be recognised by its leaves which are elliptic-oblong to elliptic-lanceolate in shape (Adams & Poole, 1980). Ranging from 7 cm up to 12 cm in length and between 3 cm to 5 cm in width when fully grown (NZ plant conservation, 2005). The leaves have a bright green and glossy upper surface with a pale green/whitish under side (figure 1). karamu grow into a bushy shrub/ small tree of 5 to 6 metres. Flowers form dense clusters with separate male and female flowers (dioecious) (Eagle, 1986). The fruit turn from red with touches of yellow to a complete red by the time they are fully ripe (figure 2 and table 1). These features, especially with the leaf shape and distinctive stipules (figure 3), help to identify karamu from the other closely related species of Coprosma.
Figure 1 Figure 2 Figure 3 Figure1 under side of leaf, Figure2 ripe fruit, Figure3 stipule of the robusta (Salmon,1997)
| Coprosma species | |
|---|---|
| C. acutifolia | C. niphophila |
| C. atropurpurea | C. parviflora |
| C. chathamica | C. perpusilla |
| C. colensoi | C. petiolata |
| C. crenulata | C. pseudocuneata |
| C. cuneata | C. repens |
| C. depressa | C. rhamnoides |
| C. dodonaeifolia | C. robusta |
| C. foetidissima | C. rotundifolia |
| C. grandifolia | C. serrulata |
| C. lucida | C. tenuifolia |
| C. macrocarpa |
Similar species
In the Coprosma genus there are many species that look similar to the karamu. In particularis the C . lucida, but this bears flowers on stalks that are well developed (Eagle, 1986). Other species that also look similar (figure 6) to C. robusta are C . australis and C. tenuifolia (Adams & Poole, 1980).
The species C . propinqua (table 4 & 5) is able to hybridize with the C. robusta species. These hybrids can then cross pollinate with either species to create more forms resembling either species (Galloway & Wilson,1993).
Figure 4 Figure 5 Picture of upper (figure 4) and lower (figure 5) surface of leaves of the C . propinqua (Salmon, 1997).
Figure 6.(Adams, N & Poole, A. 1980. page 182).
Geographic Distribution
New Zealand range
The natural range of the karamu extends throughout the South and North Islands, the Three kings Islands (Eagle, 1986) and has naturalised between Waitangi and Qwenga on the Chatham Islands. karamu is endemic to New Zealand; in fact it is naturally one of the most geographically wide spread native species within New Zealand (Eagle, 1986). Occurring from lowland to montane forests, karamu is also found in shrubland and coastal areas (Eagle, 1986). Karamu predominates in the areas along forest edges, regenerating bush margins and stream banks (Brockie, 1992).
Canterbury range
In Canterbury the karamu is found on Banks Penninsula in fragments of regenerating native bush and bush remnants. Additionally it is also found in forest margins and edges of the montane and lowland forests in the southern alps at the start of the Canterbury planes (personal observation). Coprosma robusta can also be found in the urban environment of many Christchurch city green spaces (e.g. gardens, parks and woodlots), here it is one of the more common, naturally occurring seedlings (editor's personal observations).
Natural History in Canterbury
Habitats
Karamu can be seen in the wild in montane Nothofagus forest, lowland and shrublands of bush remnants and in regenerating bush throughout the Bank peninsula and Canterbury region (personal observation).
the Coprosma genus has been around in New Zealand since the lower Oligocene period with fossil records dating back to that time (Johnson & Lee & Wilson, 1989). Today Coprosma has evolved into at least 58 species, subspecies and varieties (Eagle, 1986). Fifty percent of Coprosma shrub species have fleshly fruits; this makes up 20% of all indigenous flora that have fleshly fruits (Johnson & Lee & Wilson, 1989).
Preferred habitats
The karamu’s preferred habitat is forest margins, scrubland (Salmon, 1997) and stream banks where there is sufficient light for the plant to grow.
Phenology/Breeding
Karamu flowers are present from the start of August to the end of November followed by initiation of seed formation. Ripe fruit can be found from March to October (Brockie, 1992). The fruits of the karamu can tolerate temperatures of down to -8°C. Leaves can tolerate down to -7°C before damage to plant cells occurs (Bannister & Lee, 1989).
Life cycle
The life cycle of the karamu starts with the formation of an embryo and seed. Dispersal of the seed to a place with sufficient light and moisture will allow germination. The seedling sprouts and starts to grow; maturing into a shrubby bush up to 6 metres high. The karamu provides shelter for the next successional sere, which is the intermediate and top canopy tree layer. This canopy layer shades the karamu causing it to die through lack of light.
Dispersal
The karamu is dispersed by birds that eat the seed’s fleshly fruit. Examples of the birds involved with seed dispersal are the native bellbird (Anthornis melanura), Tuis (Prosthemadera novaeseelandiae), indigenous silvereyes (Zosterops lateralis), adventive blackbirds (Turdus merula), and song thrushes (Turdus philomelos) (Karl & Williams, 1996). This method of dispersal moves seeds over 100’s of metres to new areas; possibly areas of regenerating bush (Burrows, 1995).
Herbivores
The main pests of the karamu are herbivorous mammals which feed on the leaves, stripping the plant back and eating seedlings. Most damage is caused by goats (Capra hircus) and deer (Cervus elaphus). In addition hares (Lepus timidus) and rabbits (Oryctolagus cuniculus) also feed on young plants (Brockie, 1992).
Competitors
Competitors that compete for the same ecological niche as C. robusta are other Coprosma species (C. tenuifolia, C. australis, C. lucida) and other natives like Mapau (Myrsine australis) (McCombs, 1992); the latter being a small tree with a shrubby growth habit preferring open, well lit places.
Mutualisms
There is most likely a symbiotic mutualism between the karamu and mychorrhizal fungi in the root system. In this situation by helping to supply the plant with water and nutrients, the fungi in return access carbohydrates from the plant; as to date no research has been done in this field.
As the karamu is not wind pollinated, a mutualistic relationship with insects provides nectar in exchange for pollination. Finally a mutualism with birds, which feed on the fruits, provides the plant with the benefits of seed dispersal (Karl & Williams, 1996).
How to find the Karamu
To find the karamu, first go to an area of native bush somewhere like Okuti or Prices valley (on Banks Peninsula). Look around the bush margins, stream edges and regenerating bush. Then look for a bushy shrub/ tree with the leaf and stipule characteristics shown in the section on identification. If in flower or bearing seed, identification of karamu can be easier to confirm (personal observation).
Abundance and Conservation Status
- New Zealand: abundant
- Canterbury: abundant
Abundant throughout New Zealand the karamu is far from threatened. In Canterbury C. robusta is found throughout the bush margins and stream edges, regenerating bush and shrubland (New Zealand Plant Conservation Network, 2005).
Significance for people
Traditional Maori significance and uses
The karamu seed was used by the Maori as food. Eaten mostly by the children the seed gave a sweet taste at first to a slightly bitter after taste (Crowe, 2004). Other Coprosma species were also eaten, for example: C. grandifolia, C. lucida, C. repens, C. acerosa (Crowe, 2004).
Modern Uses
The modern uses of karamu have been limited to ornamentals and hedging in gardens, and for re-vegetation projects where it is used as a primary plant for regeneration of bush (personal observation).
Additionally the seeds of the Coprosma were ground up by European settlers to make a coffee. Being in the same plant family (Rubiaceae), the brew gave a similar taste to the actual coffee plant (Coffea arabica). Using Coprosma for this purpose did not take off because of the small size of the seeds (Crowe, 2004).
Summary
The karamu is a widely and commonly distributed, native plant through out New Zealand. Classified as abundant there is no threat of extinction. With broad leaves, the growth form and leaf structure is very similar to other native Coprosma species. karamu can be found in the margins of native bush throughout Canterbury except in the alpine and higher montane areas.
References
Adams, N., Poole, A. (1980). Trees and shrubs of New Zealand. Government print. Wellington, New Zealand.
Bannister, P., Lee, W. (1989). The frost resistance of fruits and leaves of some Coprosma species in relation to altitude and habitat. New Zealand Journal of Botany, 27, 477–479
Burrows, C. (1995). Germination behaviour of the seeds of the New Zealand species Aristotelia serrata, Coprosma robusta, Cordyline australis, Myrtus obcordata, and Schefflera digitata. New Zealand Journal of Botany, 33, 257–264
Brockie, R. (1992). A living New Zealand forest a community of plants and animals. David Bateman book. Auckland, New Zealand.
Crowe, A. (2004). A field guide to the native edible plants of New Zealand. Penguin books. Auckland, New Zealand.
Eagle, A. (1986). Eagle’s trees and shrubs of New Zealand volume one revised. Collins books. Auckland, new Zealand.
Galloway, T., Wilson, H. (1993) Small-leave shrubs of New Zealand. Manuka press. Christchurch, New Zealand.
Johnson, P., Lee, W., Wilson, B. (1989) Fruit features in relation to species ecology and dispersal. Department of Conservation report 1989 2.2
McCombs, K. (1992). Foreshore vegetation from the Waimakariri river to Taylors Mistake. Parks unit Christchurch city council report.
Salmon, J. (1997). The native trees of New Zealand. Reed books. Auckland, New Zealand
Web based resources
National plant data center, United States Department of Agriculture (USDA), Baton Rouge, LA, USA
http://plants.usda.gov
New Zealand Plant Conservation Network http://www.nzpcn.org.nz/vascular_plants/detail.asp?PlantID=1779
Search for Coprosma robusta in New Zealand science online
New Zealand Journal of Ecology articles containing Coprosma robusta.
Search NZ Royal Society journals for articles containing Coprosma robusta.
