Maple Sap and Syrup Production

Maple syrup collection in Wisconsin
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Maple syrup is a natural forest food product and, for the most part, only produced in temperate North American woodlands. More specifically, the sugary sap is mostly collected from the sugar maple (Acer saccharum) which grows naturally in the northeastern United States and eastern Canada. Other maple species that can be "tapped" are red and Norway maple. Red maple sap tends to yield less sugar and early budding causes off flavors so it's seldom used in commercial syrup operations.

The basic process of sugar maple syrup production is fairly simple and has not dramatically changed over time. The tree is still tapped by boring using a hand brace and drill bit and plugged with a spout, called a spile. The sap flows into covered, tree-mounted containers or through a system of plastic tubing and is collected for processing.

Converting maple sap into syrup requires removing water from the sap which concentrates the sugar into a syrup. The raw sap is boiled in pans or continuous feed evaporators where the liquid is reduced to a finished syrup of 66 to 67 percent sugar. It takes an average of 40 gallons of sap to produce one gallon of finished syrup.

The Maple Sap Flow Process

As do most trees in temperate climates, maple trees enter dormancy during winter and store food in the form of starches and sugar. As day temps start to rise in late winter, stored sugars move up the trunk to prepare for feeding the tree growth and budding process. Cold nights and warm days increase the flow of sap and this starts what is called the "sap season."

During warm periods when temperatures rise above freezing, pressure develops in the tree. This pressure causes the sap to flow out of the tree through a wound or tap hole. During cooler periods when temperatures fall below freezing, suction develops, drawing water into the tree. This replenishes the sap in the tree, allowing it to flow again during the next warm period.

Forest Management for Maple Sap Production

Unlike managing a forest for timber production, "sugarbush" (term for a stand of sap trees) management does not depend on maximum annual growth or growing straight defect-free timber at an optimum stocking level of trees per acre. Managing trees for maple sap production is focused on annual syrup yield on a site where optimal sap collection is supported by easy access, adequate numbers of sap-producing trees, and forgiving terrain.

A sugarbush should be managed for quality sap producing trees and less attention is paid to tree form. Trees with crooks or moderate forking are of little concern if they produce a quality sap in adequate quantities. Terrain is important and has a major influence on sap flow. Southern facing slopes are warmer which encourages early sap production with longer daily flows. Adequate accessibility to a sugarbush decreases labor and transport costs and will enhance a syrup operation.

Many tree owners have opted not to tap their trees in favor of selling sap or leasing their trees to syrup producers. There must be sufficient numbers of sap producing maples available with desirable access to each tree. We recommend you check with a regional sap producers association for buyers or renters and develop an appropriate contract.

The Optimal Sugarbush Tree and Stand Size

The best spacing for a commercial operation is about one tree in an area measuring 30 feet x 30 feet or 50 to 60 mature trees per acre. A maple grower can start at a higher tree density but will need to thin the sugarbush to achieve a final density of 50-60 trees per acre. Trees 18 inches in diameter (DBH) or larger should be managed at 20 to 40 trees per acre.

It is very important to remember that trees under 10 inches in diameter should not be tapped due to serious and permanent damage. Trees over this size should be tapped according to its diameter: 10 to 18 inches - one tap per tree, 20 to 24 inches - two taps per tree, 26 to 30 inches - three taps per tree. On average, one tap will yield 9 gallons of sap per season. A well-managed acre might have between 70 and 90 taps = 600 to 800 gallons of sap = 20 gallons of syrup.

The Making of a Good Sugar Tree

A good maple sugar tree usually has a large crown with significant leaf surface area. The greater the crown's leaf surface of a sugar maple, the greater is the sap flow along with increased sugar content. Trees with ​crowns more than 30 feet wide produce sap in optimum quantities and grow larger faster for increased tapping.

A desirable sugar tree has a higher sugar content in the sap than others; they are typically sugar maples or black maples. It is very important to have good sugar producing maples, as an increase of 1 percent in sap sugar reduces processing costs up to 50%. The average New England sap sugar content for commercial operations is 2.5%.

For an individual tree, the volume of sap produced during one season varies from 10 to 20 gallons per tap. This amount depends on a specific tree, weather conditions, sap season length, and collection efficiency. A single tree can have one, two, or three taps, depending on size as mentioned above.

Tapping Your Maple Trees

Tap maple trees in early spring when daytime temperatures go above freezing while nighttime temperatures fall below freezing. The exact date depends on the elevation and location of your trees and your region. This can be from mid to late February in Pennsylvania to mid-March in upper Maine and eastern Canada. Sap usually flows for 4 to 6 weeks or as long as the freezing nights and warm days continue.

Taps should be drilled when temperatures are above freezing to reduce the risk of damage to the tree. Drill into the trunk of the tree in an area that contains sound sap wood (you should be seeing fresh yellow shavings). For trees with more than one tap (20 inches DBH plus), distribute the tapholes evenly around the circumference of the tree. Drill 2 to 2 1/2 inches into the tree at a slight upward angle to facilitate flow of sap from the hole.

After making sure that the new taphole is free and clear of shavings, gently insert the spile with a light hammer and do not pound the spile in the taphole. The spile should be set properly to support a bucket or plastic container and its contents. Forcefully mounting the spile can split the bark which prevents healing and could cause a substantial wound on the tree. Do not treat the taphole with disinfectants or other materials at the time of tapping.

You always remove spiles from the tapholes at the end of the maple season and should not plug the hole. Tapping done properly will allow tapholes to close and heal over naturally which will take about two years. This will ensure that the tree continues to remain healthy and productive for the remainder of its natural life. Plastic tubing can be used in place of buckets but can become a bit more complicated and you should consult a maple equipment a dealer, your local maple producer, or Cooperative Extension Office.