Research Aim 2: Horticultural Row-Crop Management and Harvest

May 3, 2022

Is tree syrup horticulture viable in Aotearoa New Zealand?

Our goal is to understand the effect of climate and pruning regimes on potential syrup production. By correlating un-controlled, but measured, climatic factors to measured tree response variables (e.g. tree stem pressure, sap flow and internal tree temperature) we will refine our ability to optimise plantation site requirements.

A New Approach

Rather than relying on large tracts of natural forest and narrow climatic conditions, such as in North America, we propose for Aotearoa New Zealand an intensified horticultural row-crop, similar to an orchard or vineyard in approach.

Concept of moving away from mature forest sap harvesting and into row-crop style plantation. (Credit: Matt Rennie)

We also propose to develop new coppice pruning techniques that result in smaller plants with multiple narrow shoots, ideally suited to modern vacuum harvesting techniques. We expect that narrow stems and vacuum-harvesting will reduce dependence on freeze-thaw cycles and facilitate syrup production in milder environments and from alternative species.

We hypothesise that yields will be sustainable once the row-crop reaches maturity, expected after 4-7years.

Establishing Test-Sites

We are establishing test-sites to host small, dense plantations (e.g. 100 trees in 10m x 10m array). The suitability of sites is based on New Zealand environments with climatic conditions consistent with those in regions with successful tree syrup industries in other countries.

Our aim is to establish at least one more test-site for maple, one for birch, and one for the indigenous tree species. In selecting sites, we will identify the natural range and environmental tolerances for each species (e.g. climate, soil, rainfall etc).


Our row-crop plantations will support:

  1. A weather station and environmental monitoring devices, to measure air and soil temperature, solar radiation, precipitation, soil moisture, wind speed, and atmospheric vapour pressure deficit; and
  2. Advanced tree sensing devices, such as sap flow monitors, tree stem pressure and temperature monitors, for measuring sap composition and flow, transpiration, and other factors.

Monitoring and Data Analysis

Experiments with excised stems, and monitoring of potted and field-planted trees (in this Research Aim 2) will examine the role of sap sugar and root water uptake in sustaining flow.

Trees will be subjected to different pruning regimes to determine whether a single stem yields greater syrup volumes than multiple stems resulting from a coppice regime. Sap flow, sap yield, and sap chemical composition will be measured throughout the winter and spring months to understand how these variables vary by: tree; site; pruning treatment; climatic variables; phenological stage.

By correlating un-controlled, but measured, factors (such as rainfall, temperatures, sunshine hours, and presence/absence of leaves) to measured variables (such as tree stem pressure, sap flow/yield, sap sugar concentration and internal tree temperature) we will be able to refine our ability to optimise site requirements for each horticultural crop.

A vacuum harvest will be carried out on a selection of trees and contrasted against the sap yield from traditional gravity flow methods, in order to understand syrup yields across different pruning regimes, and maximise syrup extraction through silviculture.

The results from this research will inform and validate the predictive sap flow model (Research Aim 3).

Equipment & Processing
NZ Trial Sites
Plantation Management