Coprosma robusta
Coprosma robusta, commonly known as karamū, is a flowering plant in the family Rubiaceae that is endemic to New Zealand. It can survive in many climates, but is most commonly found in coastal areas, lowland forests, or shrublands. Karamū can grow to be around tall, and grow leaves up to long. Karamū is used for a variety of purposes in human culture. The fruit that karamū produces can be eaten, and the shoots of karamū are sometimes used for medical purposes.
Description
Karamū is a large bushy shrub that grows up to tall. Branches are stout with no hair. Domatia and stipules are significant characteristic features of Coprosmas. Karamū stipules are black, hairless and obtuse with slightly serrated margin that are united at the baseLeaves
The glossy leaves of karamū range from long, with elliptic-oblong shape and acute or obtuse leaf apex and with obvious veins. Leaves are dark green on the blade and light green on the back, are thick, and the midrib is not raised on the upper surface.Flowers
Flowers are small and white, axillary, dense, have four lobes and have a different appearance in male and females. Male flowers are dense, glomerules with a campanulate shaped corolla and have four stamens; female flowers are compound with a tubular shaped corolla. Stigmas are obvious. The best flowering period is between August and September.Fruit
Fruit are often dark orange-red to red, oblong to narrow ovate drups. The best fruiting period is between April and May.Taxonomy
The species was one of the first Coprosma species that were collected by Joseph Banks during Cook's voyage to New Zealand, who used the name Pelaphia lata in his notes. The species was first formally described by French naval surgeon Étienne Raoul in 1844.Etymology
The species epithet robusta means strong or sturdy. The Māori language name karamū has unclear etymological origins, but may be linked to the word kakara.Distribution and habitat
Natural global range
Karamū is endemic to New Zealand. However, it is gradually becoming naturalised in areas of the south-east coast of Australia such as Victoria and Tasmania and has been rated as a weed threat there.New Zealand range
It is widely distributed across New Zealand in both the North and South Islands. On the Chatham Islands between Waitangi and Owenga, there is a small area where karamū has become naturalised. They can often be observed naturally in lowland forest. Judging from the distribution map on New Zealand Plant Observation, the distribution of karamū increases with the differentiation in lower altitude which means more karamū in the North Island.In Canterbury, karamū is found on Banks Peninsula 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. Karamū can also be found in the urban environment of many Christchurch city green spaces, such as Riccarton Bush.
Habitat preferences
Karamū can be widely found near coastal, lowland and lower montane areas. It can also grow within shrub lands and expansive areas within dense trees such as lowland forest. However, the population decreases in lowland forest such as beech and kahikatea forests. Normally karamū is a hardy plant that can adapt to infertile soils, poorly drained and exposed lands. It can also grow in a large range of altitude varying from under full sun to shady, windy and frosty circumstances.Life cycle and phenology
In New Zealand the flowering season of karamū is from winter to summer. Male and female flowers are separated which is called dioecious. Seeds mature by about April and start germinating soon afterwards and doesn't leave a long lasting seed bank.The seed is largely dispersed by birds which eat the fruit. Due to its hardy characteristics, it is easy growing from seed even on open sites.
Again, as mentioned before, the best season for C. robusta fruiting is between April and May. It would finally grow up to six meters high and will normally act as a secondary succession plant during this process.
Ecology
Growing conditions
Karamū is an extremely hardy plant that can grow in a large range of environmental conditions from full sun to shady, from dry to moist, and can tolerate frost and wind. The mature fruit can endure a minimum temperature to and the leaves can endure a minimum temperature before they get irretrievably damaged. It grows best in a moist soil which is not too acid, although they have the ability to live in poor soils. They can also be found in coastal conditions, lowland scrub, swamps and rock associations.Karamū is noted for its quick bushy growth and for this reason is commonly cultivated and frequently used for native bush regeneration projects.
Predators
Herbivorous mammals such as goats and deer have a severe impact on karamū, and hares and rabbits eat the seedlings.. Additional consumers of karamū are Batracomorphus, Batracomorphus adventitiosus, leafhoppers and Membracoidea.Interactions
Birds which disperse karamū seeds include native bellbirds and tūī, indigenous silvereyes, and introduced blackbirds, and song thrushes. Seeds can be dispersed a long way and into areas of more mature forest. According to the database in Encyclopedia of Life, additional species that interact karau are Acalitus, Acalitus cottieri, Eriophyid mites, European greenfinch, and goldfinches.Karamū and mycorrhizal fungi can make a symbiotic mutualism in roots system. Because mycorrhizal fungi can supply water and nutrients to the plant. Experiments with karamū shows its growth is assisted by the presence of mychorrhizal fungi assuming there is sufficient phosphorus in the soil.