A government scheme giving away mānuka seedlings could threaten future earnings from the trees according to botanists who say enthusiasm for planting is getting ahead of scientific understanding.

Unitec associate professor Peter de Lange has been researching New Zealand mānuka and suspects there are at least three different types of mānuka in New Zealand, each with possible different properties.

“Mānuka honey as an industry is going to make us quite a lot of money but in fact there are chemical compounds, essential oils in particular, that are way, way more valuable than mānuka honey.”

De Lange said the safest way to ensure qualities are kept is to only plant mānuka where the seeds have been “eco-sourced”. Eco-sourcing means seeds have been sourced from the same area as where seedlings will be planted.

“What happens if you plant a mānuka from Northland and you plant it all around East Cape. We already know the East Cape mānuka is the one that produces the best UMF, the big wonder cure. It’s going to hybridise with it isn’t it?”

De Lange worries about unintended consequences.

“It’s inevitable but if you start mixing up mānuka and planting Northland mānuka in East Cape you’re going to dilute the future.

“Eco-sourced would have required considerably more time so we had to get the mānuka seedlings that were available, that we could lay our hands on really.”

“We know chemically there are very distinct chemical races of mānuka throughout the country and these chemicals have a lot of potential as medicine and industrial use. If you hybridise that you are going to lose that potency.”

The creation of hybrid mānuka, bred primarily for honey production, has been championed by the industry and government. De Lange fears hybrids could breed with wild mānuka and the potency of wild mānuka’s properties could be compromised.

The Ministry for Primary Industry’s forestry arm, Te Uru Rākau, announced in May it was partnering with Mānuka Farming New Zealand to plant 1.8 million mānuka trees across the country, including a variety which is a hybrid.

Forestry Minister Shane Jones said plants would be given free to landowners to be planted between July and September.

“This Government has a target to get one billion trees in the ground over the next 10 years and doing that will require innovation and genuine partnerships with the private sector, local councils, iwi and NGOs,” Jones said.

Mānuka Farming New Zealand chief executive officer Stephen Lee said he was “overwhelmed” with the applications for seedlings. Within three weeks of the offer, 185 applications were received. As a result, 1.671 million seedlings, covering 1461 hectares have been planted. Over 500,000 were a hybrid high-performance variety.

“There were no eco-sourced ones at all. Eco-sourced would have required considerably more time so we had to get the mānuka seedlings that were available, that we could lay our hands on really.”

Seedlings were sourced from Kauri Park Nurseries, one of the largest remaining native plant nursery in New Zealand, Comvita, and a small amount were supplied by Mānuka Farming New Zealand.

Lee said: “We matched the location to the provinces of the stock. There would be a little bit of a crossover, but you wouldn’t put something from Northland in Wairarapa or Taranaki. There’s a high risk of things not working out. There was a matching process if you like.”

The hybrid high-performing variety was bred over seven years, according to Lee, and selection criteria was based on flowering density, sugar content and levels of chemicals responsible for mānuka honey’s antibacterial quality.

Improving the crop which honey bees feed on is big business.

Despite an increase in export earnings from honey, and an increase in the number of hives, production per hive is decreasing. An MPI apiculture report showed per hive only 18.7 kilograms of honey was harvested in 2017. It’s part of a downward trend in volume from a high of 39.4kg in 2013.

The low per-hive yield was put down to a variety of weather-related factors including heavy rain in some areas and high winds in others. The number of hives is also increasing, which impacts on the individual hive as food sources are shared between an increasing number of bees.

Lee said the free seedlings initiative “contributes to both the Government’s One Billion Trees Programme and helps to achieve the goal of growing mānuka honey earnings to $1.2 billion by 2028”.

According to Lee, most of the hybrid mānuka were planted around the centre of the North Island.

“It’s happening so quickly, and I don’t think there has been that public discussion about what we want.”

University of Otago associate professor Doctor Janice Lord wonders if there’s a case for planting non-local mānuka to require resource consent.

“Large-scale planting of foreign or non-eco-sourced mānuka into areas where there are existing wild mānuka populations does represent a certain amount of risk.

“The interest in mānuka and the huge enthusiasm about planting it is getting ahead of our scientific understanding of how many entities have we got here and are some of them rare. Do they even hybridise? We don’t know.”

She acknowledges there may be frustration growing at “scientific reticence” but like de Lange warns about losing qualities of wild mānuka through cross-breeding.

“There still could be properties found in different types of mānuka in different parts in the country and you wouldn’t want to lose that genetic resource by too hastily planting what’s considered the best mānuka at the moment into areas where there is wild mānuka.”

Lord said she is enthusiastic about the Billion Trees project and its potential to re-clothe land stripped of trees but thinks there needs to be conversations around the goals.

“It’s happening so quickly, and I don’t think there has been that public discussion about what we want.”

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