The plant species studied included karo (Pittosporum crassifolium), kōhūhū (Pittosporum tenuifolium), tarata (Pittosporum eugenioides), kōtukutuku (Fuchsia excorticata), pōhutukawa (Metrosideros excelsa), mānuka (Leptospermum scoparium) and kōwhai (Sophora microphylla) and tī kōuka (cabbage tree).
The regions were Auckland, Taranaki, Hawke’s Bay and Wellington in the North Island, and Nelson/Tasman, Marlborough, Canterbury and Dunedin in the South.
Researchers found trees like kōwhai and pōhutakawa produced the highest concentrations of nectar in drier areas, while sunnier sites generally had lower nectar volumes, though larger flowers.
Results from mānuka flowers showed substantial regional variation in nectar traits, driven by climate.
University of Waikato researcher Dr Johanna van Delden said the study could benefit conservationists and beekeepers, the latter to help them decide the most optimal locations and nearby trees for their beehives.
“The trees which produced the most sugar of all the species were either found in Dunedin, Canterbury or Hawke’s Bay, which are all on our east coast.
“And the nectar volume, so how much nectar each flower produced, was also in 50% of the species coming from Dunedin or Hawke’s Bay.
“So I think that was the clearest and easiest result we could take out of our measurements.”
She said researchers were surprised by how the plants differed across climates.
“We found that every plant is really different.
“So we could see that some plant traits, like nectar or the flower size, was climate-linked, but it really varied from species to species between 20 and 80%, which is a massive variation.
“It was mostly associated with sunshine hours and rain amounts to really simplify the results.”
Van Delden said farmers could look at the species that performed well in their region to encourage greater biodiversity around farms.
“When they are flowering, attracting butterflies and birds, that could enhance your backyard biodiversity and could be used also on pastures for shelter.”
She said further research should explore how the native plants adapted to local climates across the country.
“If we go one step further, so the next researcher after me could have a look if it’s actually not the location itself having the influence on the plant, but actually that it’s genetically driven.
“So that the plants over time have evolved in that way, that they are adapted to that local climate and therefore show those adaptations in regards to producing more sugar, for example, in the South Island and east coast.”
Part of the research was funded by the Government’s Endeavour research programme by the Ministry of Business Innovation and Employment, entitled “Building Resilience and Provenance into an Authentic Māori Honey Industry”.
It was a joint project with the University of Waikato, Manaaki Whenua/Landcare Research and the Auckland University of Technology.
- RNZ
