Did you know
The rātā and pōhutukawa belong in the myrtle family of trees. Other members include mānuka, kānuka and swamp maire.
Rātā 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 kākā all benefit from the presence of rātā trees in the forest.
The two main types of rātā are the northern and southern. Bartlett's rātā is endangered and very few remain.
Northern rātā (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 rātā (Metrosideros umbellātā) grows from a seed in the ground to become a tree up to 15 metres high with a trunk 1 metre through.
Southern rātā is the most widespread of all New Zealand rātā. 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 rātā occurs along the South Island's West Coast
Bartlett's rātā (M. bartletii) has white flowers and pale, papery bark, which make it unique among New Zealand rātā. 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
As possum populations have built up in forest areas, there has been a corresponding loss of rātā and some other forest species.
Possums eat a wide range of plants, but show strong preferences for some species like the rātā. Studies have shown that they will often browse one or a few trees, while ignoring others of the same species nearby.
Rātā 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 rātā and other species is even greater.