Within the Myrtaceae family, pohutukawa and rata belong to the genus Metrosideros which contains five New Zealand tree species. Project Crimson focuses on all of these except the Kermadec pohutukawa as this is naturally restricted to the Kermadec Islands, about 900km north-east of New Zealand.
Mainland pohutukawa (Metrosideros excelsa)
Metrosideros is the Greek word for ironwood, which reflects the hard nature of the timber. The species name excelsa is derived from the Latin word meaning "raised" or "exalted". A former name, Metrosideros tomentosa, described the felt of white hairs (tomentum in Latin) which covers young stems, buds and undersides of the leaves.
Found throughout the North Island, particularly north of New Plymouth and Gisborne. Pohutukawa grows best in warm, drier areas close to the sea.
Grows to 20 metres high by 35 metres wide.
Northern rata (Metrosideros robusta)
Found from Hokitika northwards. It usually begins life as an epiphyte (perching plant) high in the forest’s canopy. The largest trees are found in warm moist areas such as northwest Nelson and Northland. Northern rata grows from the coast to a maximum of 900 metres above sea level.
One of New Zealand’s tallest flowering trees. Grows to 25 metre or more high with a trunk up to 2.5 metres in diameter.
Southern rata (Metrosideros umbellata)
Grows throughout New Zealand, particularly along the South Island’s West Coast. Best suited to South Island and cooler, high rainfall regions. Occurs from sea level to 760 metres above.
A forest tree, it is found on rocky slopes and in river gorges from coast to mountain in the south and west of the South Island. It is restricted in the North Island to isolated stands or single trees on elevated cool damp sites.
Grows to 15 metre high – sometimes more - with a trunk up to 1 metre through. Considered to be an ancient species from which northern rata and pohutukawa evolved.
Bartlett’s rata (Metrosideros bartlettii)
Discovered in 1975 as a small, isolated population at the northern tip of the North Island. Rātā moehau (Bartett's rata) is critically endangered with very few adult trees remaining in forest remnant near Cape Reinga.
Trees grow up to 20 metres high by 6 metres wide and have a bark similar to that of the paper-bark myrtles in Australia. They usually develop as perching plants in the canopy of the host tree.
Roots are formed and eventually reach to the ground, coalescing into a single trunk which in due course replaces the host.
How fast do the trees grow?
Young plants grow faster than older plants. In a very fertile environment with good moisture and plenty of room, young pohutukawa grow at around 30cm per year in height and 5-10mm in diameter (thickness). Older trees gain around 10cm in height a year and 2mm in diameter. Rata grows at about half the rate of pohutukawa.
How long do they live?
Pohutukawa can live for hundreds of years in their natural coastal environment. While it is common to see 100-year-old trees growing in home gardens, both pohutukawa and northern rata can probably live up to 1000 years.
Both pohutukawa and southern rata can spread by branches that touch the ground sending out roots and forming new trees. As a result it is impossible to accurately assess the age of trees that have grown in this manner.
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