The Natural History of Maple Syruping

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We started tapping maple trees on campus this week. I would guess that most of my readers are familiar with the general process of making maple syrup – you tap the trees to collect their sap and boil it down to get rid of the excess liquid and concentrate the sugar. The Ojibwa Indians in this area were already collecting sap to make syrup and sugar before the first European settlers arrived, and there’s even a town south of here called “Sugar Camp” because the site was known as a center of maple tapping activity. But why do we tap the trees at a specific time of year? What exactly is going on with the sap?

Well, first, what is sap? Duh, we all know it’s the sticky liquid in trees, but it has an important function. Sap flows through a tree’s xylem and phloem (remember your high school biology?), bringing moisture and nutrients from the roots up to the leaves and taking sugar and other carbohydrates produced in the leaves back down to the roots for storage. This is roughly (very roughly) analogous to an animal’s circulatory system.

The ideal time to tap a tree to collect sap is early in the spring when temperatures are above freezing during the day but below freezing at night – basically right now, if you live here in northern Wisconsin. The most commonly accepted theory for why sap flows at this particular time of year is that as temperatures rise and fall each day, carbon dioxide within the tree’s tissues expands and contracts, creating a cycle of pressure that causes sap to flow out of any wounds in the tree during the day and suction that causes water to be drawn up from the roots at night. This is a separate process from the water tension and cohesion that usually drives the movement of moisture up and down the tree.

Sugar maples and other closely related species have particularly high amounts of sugar in their sap, which makes them ideal for making syrup, but some sources I found suggested that another reason maples are particularly suited for tapping is that the structure of their internal tissues makes this pressure cycle more pronounced in maples than in other trees. Even with the relatively high amount of sugar in sugar maple sap, it takes about forty gallons of sap to make one gallon of syrup.

So, have you ever done your own maple syruping? One of the very first posts on this blog was actually about the syruping process, way back in March 2010. I can tell you this much, real maple syrup is way better than the cheap fake stuff in the grocery story.

Further reading:
Sap Flow
Biology of Maple Sap Flow

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7 thoughts on “The Natural History of Maple Syruping”

  1. Yes! Oh, you’ve touched on a topic dear to my heart–we tapped our own trees when I was growing up in Geauga County, OH. I still have fond memories of sucking on sapcicles as we emptied buckets; sitting outside by a warm, sweet-smelling fire in February snow; and being too impatient to wait for my maple stir to reach its proper consistency before eating it.

    My hometown, Chardon, has a Maple Festival every spring, and my dad won first prize in the Amateur Syrup division the first year we sugared (I found out just recently that he’d run it through a centrifuge or something in his lab to get the sugar content exactly where it was supposed to be–but I suppose the statute of limitations has run out on that by now).

    And yes, once you get used to the real stuff, there’s no going back! I’m a total syrup snob.

    Judging by your photo, they’re still using the traditional metal buckets on campus. Are there any areas where they’re using plastic tubing?

  2. In New Jersey, where I work runs a Maple Sugaring Program as a demonstration project only. (We tap one tree and get about one bucket a year). We’re just wrapping up. The last maple sugaring programs will be taking place through this week and that should be it. We began in January to help the local Jewish community celebrate Tu BiShvat (New Year for Trees) and sap was already running. So we’ve been operating for about 8 weeks now. Ironically it’s so cold, the sap stopped running.

  3. Reblogged this on Dreaming the World and commented:
    We came home to 19 degree F weather. Today we have light snow.
    The annual maple sugaring is underway. Next week we do ceremony to honor the Maple tree and maple sugaring. Apparently last week marked a good run of sugaring. Here is an explanation of the nature of sugaring.

  4. I met a guy here in KC who tapped his trees on some property in La Cygne, Ks (usually, the only things being cooked up in shacks in the woods around here is meth) it was wonderful stuff, but somehow I lost track of him and never got to help him do it. When first tasted REAL maple syrup, I felt like I had squandered my childhood, being hoodwinked by that vile Mrs. butterworthless and that corn syrup. It took 10 years before the rest of my family put down the fake goo. But what I still can’t believe is that people here in the mid-midwest actually put karo syrup on pancakes! On purpose! They claim it’s made from corn but I still think it’s a petroleum biproduct.

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