Friday, February 20, 2009

Makin' Maple Syrup

Right now, Southeastway Park is smack-dab in the middle of maple syrup season. Our syrup making season is February to mid-March. This means loooonnnnggg days of collecting sap, carrying wood and watching sap boil. And, I am a great sap-boilin'-watch'r, I tell you whut!

The process at Southeastway all starts with the Sugar Maple tree (Acer saccharum), one of autumn's most visually pleasing trees. This is the tree used traditionally in syrup making. Other maple species, hickories and tulip trees can be used to make syrup, but the other tree species have sap with a lower sugar content. Their sap contains around a 1% sugar content, so it will take 80 gallons of sap to make one gallon of syrup instead of the usual 40 gallons of sap needed from the sugar maple. The sugar maple has 2% to 3% sugar content in its sap.

I had to throw this picture in from Wikipedia showing the range of colors that can be observed in the sugar maple. Deep yellows, fiery reds, crimsons and even purples can grace the same tree in the fall.

We tap the trees in early February, when the nights are cold and the days are above freezing. These are the days when the sap runs the best. I will explain why in just a bit. Farther north, where it is a bit colder, production doesn’t start until late Feb-early March and runs into April.

Tapping of trees, if done correctly, will not harm the tree. We drill into the tree with a 7/16th bit (simialr in size to ones pinky) about an inch and a half into the sapwood at a slight angle. We use a hammer to tap in the spile, the metal doo-hickey sticking out of the tree in the above photo.

Due to pressure in the tree, the sap will begin to flow almost immediately after tapping. Since the hole is drilled in at a slight angle, the sap drips out of the hole more easily. We hang buckets from the hook on the spile to capture the sap. There is a custom-made lid for each bucket to keep out debris and rain.

The sap is clear in color. There is a puddle of sap in my palm, really. If you look closely, you can see it glistening. You may wonder, how does maple syrup turn golden brown? Well, just as white bread turns golden brown when toasted, the sugars in the sap turn a lovely amber color when cooked over a long period. I will share a funny story-when explaining this to a group of kindergarteners, one exclaimed "My toast is always black because Mommy burns it. " Poor Mommy, she was standing right next to him!

After the season is over in mid-March, we will pull out the spiles. The cambium layer of the tree will “heal” the hole left in the tree by producing new cells that plug the hole. This is last year's tap mark in the center of the tree.

We tap between 50-60 trees. Some we attach a bucket and spile combo, some we use a more modern plastic bag, and on one group of trees in the above photo we use the most modern tubing method. A series of trees along a slope are tapped and tubing is strung between them. Gravity will pull the sap down the tubes drop by drop. We have a large container at the end of the line to collect all the sap from the six or seven trees. This way, only one container needs to be emptied instead of seven. More efficient. This is the method the large producers use, only they have many more trees connected.

Tomorrow, we will discuss how we turn the sap into delicious syrup.
But wait, for you science nerds, there is more. Here is an explanantion on how the sap travels in the tree, driven by atmospheric and internal pressure and temperature fluctuations. It made sense, but at the same time made my head hurt. You are forewarned.
Maple sap flow may occur anytime during the maple tree's dormant season when temperatures hover around the freezing point. In Indiana this can occur October through the following mid-March. The largest flows take place during the months of February and March. During this time, we frequently have freezing temperatures during the night and warmer days . When these warmer daytime temperatures are followed by below freezing periods, usually at night, strong sap flows can be expected.
How does this happen? Here is one explaination I found online. "Current theory suggest that when temperatures fall below freezing, negative pressure (suction) is created within the sapwood of maple trees as a result of sap freezing, carbon dioxide dissolving in cooled sap, and gas contraction during cooling. As a result of this negative pressure, water moves from the soil into the tree increasing the sap volume. When the temperature then rises above freezing and the frozen sap thaws, forces (including pressure from released gases, osmotic, caused by the presence of sugar and other substances dissolved in the sap, previous gas compression, and gravity) act on the increased sap volume to create a positive pressure. This pressure develops first in the twigs, then in the trunk, and finally in the roots of the maple tree. The positive pressures that develop can be considerable, rising to 40 or more pounds per square inch in untapped trees. When temperatures fall, the process is reversed and pressures are reduced. Below freezing temperatures are required for strong negative pressures to again develop. Much weaker sap pressures develop if below freezing temperatures are not reached and sustained long enough for ice to form within the tree. The presence of sucrose in sap may also be involved in the maple sap flow mechanism. Sap flow occurs when a wound is made in the sapwood of a maple tree which has positive sap pressure. Sap flow from the wound will continue as long as the pressures inside the tree are greater than atmospheric pressure outside the tree. This period of sap flow (pressure dissipation) will vary from a few (1 or 2) to several (15 to 20) hours in length. Length of the sap flow period and the amount of sap produced appear to be affected by several environmental and tree metabolic factors including the minimum and maximum temperatures experienced, sap sugar concentration, the duration of the freezing and thawing cycles, and the availability of soil moisture. For strong sap flows to be repeated, a suitable temperature cycle above and below freezing must again occur to allow strong positive sap pressure to develop. Sap flow temporarily ceases during the "maple season" when suitable temperature cycles do not occur (cold or warm periods) and ceases entirely when suitable temperature cycles end for the year. " Nuff said!
Also, we cannot make maple syrup in Indiana much past March 15th because the tree starts to use the sugars to form leaves and the syrup takes on a bitter taste. Plus, warmer temperatures spoil sap quickly. A lose/lose situation.
Anyway, tomorrow we make syrup!

1 comment:

Tap My Trees said...

Great information. For those looking to tap a few trees at home, check out for a detailed description of the process.