What if Aotearoa New Zealand could create a sustainable primary industry based on premium, high-value tree-syrups (e.g. maple, birch and other tree species)? A team of researchers and landowners have been exploring this opportunity for the past few years.
Tree syrup is produced by concentrating the sugars found naturally in sustainably harvested tree sap. Conventional wisdom was that maple sap production couldn’t occur in New Zealand because the weather is too mild. This assumption, from the traditional maple industry, is that a freeze-thaw cycle is an essential part of sap production processes. However, sap exudation has been shown to occur at temperatures around 3°C, so fluctuations in temperatures close to 0°C are sufficient for sap flow to occur. This means Aotearoa’s climatic conditions, in colder regions, are sufficient to enable maple sap flow.Sap collection takes place from June to August. Entrepreneurial landowners in the Nelson region (in 1984) and Otago region (in 2020) have invested in traditional maple growing methods which use mature trees.
The Tree Syrup Aotearoa research programme (2021-2024) aims to match tree growth with sap yield and to understand the tree sap exudation mechanisms. However, rather than focusing on old trees, the team are examining the potential of young trees. This approach uses a closely spaced, horticultural-style row-crop, similar to an orchard or vineyard, developed by researchers at the Proctor Maple Research Centre in Vermont.
Researchers are studying the effect of climate and coppicing regimes on potential syrup production. The University of Canterbury-led team have partnered with landowners to establish 100-tree test plantations in Canterbury. Sugar maples (Acer saccharum) were planted near Hanmer Springs in 2020 and near Geraldine in 2022. In 2023, red maples (Acer rubrum) and paper birch (Betula papyrifera) were planted by a landowner near Pleasant Point. The saplings were planted in 10m by 10m plots with 1m spacing.This may sound like very dense planting, but this system relies on frequent coppicing, so trees have a small stature.
The initial research focus is maple, but birch syrup has an even higher value, while syrup derived from native trees could enable a protected geographical indication (like scotch to Scotland) and further support a nationwide tree syrup industry. Many trees/plants have importance to Māori and there is Mātauranga Māori (indigenous knowledge) on extraction for rongoā (medicine), food and drink from indigenous trees. Yet the published literature has little mention of sap content or chemical composition in native New Zealand plant species (except formanuka and kanuka). A Masters-level student is exploring this potential as part of his research project, with possible candidates including tarata, matai, miro, rata and even, perhaps, pohutukawa.
To complement the field-based research, the team are using cutting-edge imaging techniques to study cells and structures inside the stems of a sugar maple tree, and were the first to use x-ray computed tomography to create a 3D image of the inside of a living maple trunk. High-resolution imaging systems are being used to look inside cut stems and living saplings to understand the behaviour and movement of sap and gas bubbles. These data and images help the team to understand the mechanisms that lead maple trees to produce high volumes of sugar-rich sap.
To deliver this research requires innovative technology development. A new non-invasive sensor is being tested to measure sap flow in saplings – because the probe-based sensors used in large trees are not appropriate. Also, a bespoke test rig has been developed to freeze and thaw a sapling under accurate, controlled, laboratory conditions, which is then used to image the microstructures inside the stems when this freeze-thaw cycle is in progress. Looking forward, the research programme aims to vacuum harvest a selection of trees to extract and analyse some maple sap from the plantations this winter.
Matching tree species to New Zealand conditions could allow an alternative, higher-value use for marginal land, support regional development, and produce an exportable product. Though the research funding ends later this year, a wealth of information has been compiled and is available (for more information, visit www.treesyrup.nz).
It is still uncertain if tree syrup is a viable commercial prospect for New Zealand, but there is a small and passionate group of people willing to find out!
