A northern rata in flower in Otangaroa Forest. Grey branches on the rata and neighbouring trees are due to possum attack but flowering shows the rata is coming back to life. Photo / Toby Ricketts
A northern rata in flower in Otangaroa Forest. Grey branches on the rata and neighbouring trees are due to possum attack but flowering shows the rata is coming back to life. Photo / Toby Ricketts
Northern rata in some Northland forests are turning a brilliant red as the trees burst into a once-in-a-decade explosion of flowers.
The phenomenon can only be seen, however, in forests with extensive pest control because the northern rata is a favourite food of the possum — and the forest giants also face a new threat from the plant disease myrtle rust.
Dean Baigent-Mercer talks about northern rata:
Dean Baigent-Mercer, Northland conservation advocate for Forest & Bird, said drone footage taken over Otangaroa Forest, north of Kaeo, showed flowering on a scale which happened just once a decade.
The forest had been subject to multi-species pest control targeting possums, rats, stoats, weasels and feral cats for the past seven years.
The images showed tell-tale signs of past possum damage such as grey, leafless branches, but pest control meant the trees were still able to flower prolifically.
Mr Baigent-Mercer said research had shown possum-wrecked native rainforest canopies could recover if possum numbers were kept close to zero for 20 years.
The drone footage showed northern rata in Otangaroa Forest were coming back to life, but dying in places like Russell State Forest without comprehensive pest control.
A northern rata in flower in Otangaroa Forest. Grey branches on the rata and neighbouring trees are due to possum attack but flowering shows the rata is coming back to life. Photo / Toby Ricketts
"Native rainforest canopies should be lush greens but the greyness you see in the drone footage is from decades of possum attack. The flowering northern rata has basically dodged a bullet thanks to pest control and is starting to recover. But in areas nearby without pest control the forest is slowly collapsing,'' he said.
The trees' future had been made even more uncertain by the arrival in New Zealand of myrtle rust, a fungal disease which attacks trees of the Myrtaceae family such as rata and pohutukawa.
Myrtle rust's first appearance on the New Zealand mainland was in a Kerikeri plant nursery last May. It has not been reported in Northland since last year's major biosecurity operation but its return is thought to be only a matter of time.
That made it even more important to make the most of the current heavy flowering and the abundance of seed that would soon follow, Mr Baigent-Mercer said.
The seeds died within weeks if they didn't find a place to germinate.
How to collect and plant northern rata seed:
In a bid to help the trees regenerate Forest & Bird had made a short video showing how to collect seed and grow northern rata, he said.
According to the Ministry for Primary Industries, myrtle rust is continuing its spread around New Zealand. It is now in Waikato, Bay of Plenty, Taranaki and Wellington; in November it was found in Auckland for the first time. No new cases have been reported in Northland since May 25.
■ Myrtle rust affects native trees such as rata, pohutukawa and manuka as well as common garden plants including lilly pilly, feijoa, eucalypts and bottle brushes. It starts as a purple patterning on the leaves that turns into bright yellow spores. If you suspect your plants are infected, don't touch them but call the MPI hotline on 0800 80 99 66.
