New Methods for Plant Growth & Sap Collection

August 17, 2022

The sap from sugar maple (Acer Saccharum Marsh.) trees contains high levels of sugar, which is collected for the production of maple syrup. Freezing spring nights and warm spring days in North America play a pivotal role by getting the sap flowing in big, old maple trees, which can then be collected and processed into syrup.

Our research is looking to the potential of alternative tree species and matching these tree species to New Zealand conditions. Also, rather than focusing on old trees, we are examining the potential of young trees, in a closely spaced, horticultural-style row-crop, similar to an orchard or vineyard in approach. We propose to develop new pruning techniques that result in smaller plants with multiple narrow shoots, ideally suited to modern vacuum harvesting techniques.

Traditional Tapping Practices

Sweet sap is collected from mature maple trees, older than30-40 years, through a process known as tapping. The short sap-harvesting season (i.e. ‘sugaring season’), is usually about a six-week period in the springtime. Maple sap begins to flow in late winter as ambient temperatures rise above 0°C, after an extended period of sub-zero temperatures, and will continue to flow until late spring, when buds begin to break.

To tap a tree, a small hole, about a centimetre in diameter and four to six centimetres deep, is drilled into the trunk or stem of the tree and a small spout inserted. Collection initially relied on the natural tree pressure and gravity. Bucket collection was replaced by tubing systems by the 1980s. More recently, the use of vacuum extraction techniques has increased the amount of sap extracted.

A sugar maple tree with tap holes drilled and tubing inserted to transport the exuded sap from the trees (Credit: iStock)

Row-Crop Style Horticulture & Vacuum Harvesting

Research from the University ofVermont’s Proctor Maple Research Center has shown it is possible to produce maple syrup from young (less than ten years old) maple saplings. This means production of maple syrup might be possible in different climates(without freeze-thaw cycles), using a combination of smaller diameter saplings and vacuum extraction techniques.

Perkins and van den Berg discovered that sap containing sugar, similar to that collected from mature trees, could be collected from the stem of saplings excised at chest height. They established a novel method of sap collection consisting of de-crowning the top of the maple sapling and covering the exposed stem with a collection device. A partial vacuum is applied so sap flows from the top ends of the stems through tubing to the collecting tank.

A key requirement for an intensified horticultural row-crop is regeneration of new growth from the cut stems. Our research is exploring 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.

More about our planned research on pruning techniques is here.  

Concept of pruning techniques suggested for maple sap extraction from small-diameter sugar maple saplings. The left image shows a single-stemmed sapling, de-topped for sugar maple sap exudation, which is what we are currently trialling at our Hanmer trial site. The right image shows three stems extending from the same root system. The vacuum extraction system is attached to a single stem each season, allowing the other stems to recover and grow. Plastic tubing runs from each sapling, collecting the sap from each sapling and pulling it to a common collection point. (Credit: Tenaya Driller).

Plant Physiology
NZ Trial Sites
Plantation Management