Did you know
The rata and pohutukawa belong in the myrtle family of trees. Other members include manuka, kanuka and swamp maire.
Rata trees have glossy dark green leaves and trunks that are often gnarled and twisted. However they are best known for their brilliant red flowers that appear in profusion from November to January, depending on location, and can be seen from some distance away.
The trees tend to flower well only once every few years and seem to favour the high rainfall conditions of the West Coast.
Native birds such as the tui, bellbird and kaka all benefit from the presence of rata trees in the forest.
The two main types of rata are the northern and southern. Bartlett's rata is endangered and very few remain.
Northern rata (Metrosideros robusta) is one of New Zealand's tallest flowering trees. It usually begins life as an epiphyte (or plant perched on a host tree) high in the forest canopy. Its roots grow down to the ground, finally enclosing the host tree and producing a huge tree up to 25 metres high with a trunk of 2.5 metres through. It is found throughout the North Island and in the South Island, south to about Westport.
Southern rata flowers
Southern rata (Metrosideros umbellata) grows from a seed in the ground to become a tree up to 15 metres high with a trunk 1 metre through.
Southern rata is the most widespread of all New Zealand rata. It is found from sea level to 760 metres. It is distributed from high Northland and Coromandel outcrops, to subantarctic Auckland Islands where it forms the country's southernmost forests. The most dense display of southern rata occurs along the South Island's West Coast
Bartlett's rata (M. bartletii) has white flowers and pale, papery bark, which make it unique among New Zealand rata. This species was discovered in a forest remnant near Cape Reinga in 1975 and is listed as endangered. Very few adult trees remain.
Threats from possums
Possum browse on Northern rata
As possum populations have built up in forest areas, there has been a corresponding loss of rata and some other forest species.
Possums eat a wide range of plants, but show strong preferences for some species like the rata. Studies have shown that they will often browse one or a few trees, while ignoring others of the same species nearby.
Rata trees cannot tolerate browsing. A mature tree can be killed in three years with intensive browsing and even young trees, although they can survive for longer, will eventually die if browsed regularly.
When the browsed trees eventually die back, the canopy, or top layer of the forest, is then opened up. Once the canopy is open, the trees are exposed to storms, insects and diseases and will suffer further.
Because possum numbers have increased dramatically in recent years, the threat to rata and other species is even greater.