A few years ago, we posted a video about making our own maple syrup as well as the science
behind maple sap.
And in response, we’ve received a number of questions about the process.
But one question in particular has stuck with me ever since, and so this year while preparing
to tap our trees yet again, I decided it was about time we finally got to the bottom of it.
So in this video, we’ll attempt to discover whether or not collecting maple sap hurts
the tree.
But if you haven’t already, I’d first encourage you to check out that original video
for some background information, so as usual, I’ve placed a link in the description.
But for everyone else, here’s a really quick recap.
Throughout the year, maple trees produce carbohydrates (or sugar) through the process of photosynthesis.
Now, they do this because, like us, trees use carbohydrates as fuel, which they circulate
throughout their bodies suspended in water.
And also like us, whatever fuel doesn’t get used right away, gets stored for future use.
So by the end of the summer, once the weather turns cold, all of that sap collects in the
trunk and roots, where it eventually freezes as the tree goes dormant for winter.
Then in the spring, as the below zero nights turn to above zero days, the warming sap expands
back up into the branches where it’s used to produce new leaves and get the whole process
started all over again.
So when we drill a tap hole, we’re actually creating an opening for some of that expanding
sap to escape.
But if sap is essentially food for the tree, doesn’t stealing some of it cause a problem?
Well, from my research, most seem to agree that the tree already produces more sap than
it needs, so as long as we don’t take too much, it shouldn’t result in any major lasting effects.
However that still leaves the tap hole itself, because I must admit, it does feel a little
unnerving drilling into the side of a living organism.
But to understand whether or not it’s actually a problem, I think we’ll have to dig a bit
deeper, and talk about some tree anatomy.
So first of all, we’re all familiar with the growth rings that can be seen on a freshly
cut log, branch, or stump.
Each of these represent a year of the tree’s life, so by counting them, we can accurately
determine the trees age.
And by examining their appearance, we can even deduce the kind of weather conditions
it experienced throughout the seasons.
For example, wider rings typically indicate warm years with above average rainfall, because
the extra water and sunshine allowed the tree to put on extra growth.
But you’ll also notice that the rings on the inside of the tree tend to be quite a
bit darker than those on the outside.
And that’s because as the tree grows older, the cells that make up the earliest rings
actually die.
And when they do, chemicals are released that make them stronger but also change their colour.
This is called the heart wood, and don’t worry about the fact that its technically dead.
This is a normal healthy part of a tree’s growth and stability.
Think of it almost like the tree’s skeleton.
And then on the outside of the heartwood, you’ll also notice lighter coloured rings,
which are typically referred to as the sapwood.
These are the cells that are still alive, and as the name suggests, they’re responsible
for the transport of water and stored sap up the tree.
Think of them almost like the tree’s veins and arteries.
And finally there’s the outer-most ring, right below the bark.
This is called the cambium, and it’s the part of the trunk that’s not only still
living, but also still growing.
You see, this ring is constantly generating new sapwood cells on the inside, and bark
cells on the outside.
Which means that it’s responsible for creating every growth ring all the way back to the beginning.
And for that matter, it’s responsible for every future growth ring as well.
So without the cambium, tree trunks could never grow wider, and as you’ll see in a
moment, they could never fully heal themselves either.
Ok, so that’s all of the relevant parts that you can see in a cross section, but there
is one more important structure that I should mention as well.
These are called the ray cells, and though they’re not always visible to the naked
eye, they extend out from the center of the trunk in varying lengths.
But for our purposes, let’s simplify them a bit and just say that they divide the rings
into wedges, almost like the slices of a pie.
Alright, I think that’s enough anatomy for now.
When we drill into the trunk of a maple tree, we’re essentially severing the individual
cells of the sapwood.
And so all of that nutrient-rich water quickly begins to escape from the openings.
But again, does this hurt the tree?
Well I guess that depends on what you mean by hurt.
For example, trees obviously don’t have a nervous system and they aren’t sentient
or conscious, so it’s unlikely that they feel pain or experience anything like suffering.
However, it’s still pretty clear that this does cause some physical damage.
So in that sense, the tree has obviously been injured.
But luckily, like any other organism, the tree also has the ability to recover from it.
For example, this is a tap hole that we drilled last year, and as you can see, it’s already
nearly sealed up.
But the tree isn’t healing it’s self in the same way that my finger does when I accidentally
poke it with a thumbtack.
There are some similarities, but as you’ll see, there’re some pretty big differences too.
For instance, my blood cells quickly clump together to form a clot, keeping the blood
loss to a minimum.
And once that clot dries out, the resulting scab forms a physical barrier to keep bacteria
and other contaminants at bay.
And the tree has a similar function.
Because eventually, once the spile and bucket are removed, the sap begins to gum up the
severed cells above and below the tap hole.
This helps to prevent additional sap loss, and is also the first line of defence against
invading fungus and bacteria.
More on them in a moment.
So, the first stages of healing are surprisingly similar.
But while my finger quickly begins to repair damaged tissue and fill in the wound with
new cells, the tree has an entirely different strategy.
Because, thanks to the cambium, trees are really good a growing new cells on the outside,
but unfortunately they don’t have the ability to repair or grow new cells on the inside.
So instead, trees reply on a process called “CODIT” or the Compartmentalization of
Decay in Trees.
The first step of compartmentalization is that gumming up of the cells above and below
the wound.
These form the top and bottom walls of the compartment, and help stop the spread of decay
up and down the trunk.
Next comes the back wall, which is actually just the outer-most undamaged growth ring.
This helps stop the spread of fungus and decay further into the center of the tree.
And then we have the ray cells, the ones that divide the tree like the slices of a pie.
They form the side walls and help prevent decay from progressing around the trunk.
And finally the front wall is created by the cambium, because remember it’s the only
part of the trunk that can actually generate new cells, so it slowly seals up the wound
from the outside.
This is the strongest line of defence and it prevents any new fungus from entering the
tree, but unfortunately it also takes by far the longest.
Like our tap holes from a year ago, that are still sealing up today.
So a year or more is a pretty long time for the tree to be exposed, and to make matters
worse, those inner compartment walls don’t hold up forever.
Typically, the top and bottom walls are the first to give way, and so decay spreads quickest
in the vertical direction.
But luckily, the tree does have one more defence up it’s trunk.
Remember how the dying cells of the heartwood release chemicals that make them stronger
but also discolour them?
Well the dying cells around the tap hole do the same thing.
But the chemical is also toxic to many forms of fungus.
So as the decay slowly breaks down the walls, and infects neighbouring compartments, the
surrounding wood also becomes a less hospitable environment for the fungus to grow.
So assuming the wound was small enough, and the infection was weak enough, by the time
the cambium seals off the opening, the tree will have isolated the decay to a collection
of discoloured compartments.
And this is why maple trees that have been tapped throughout their lives, tend to produce
such attractive grain patters in their lumber.
The darker wood is actually the result of spreading decay and the tree’s chemical
response.
But that’s not the only lasting reminder of maple syrup production, because again,
the tree can’t fill in the tap hole, it can only ever cover it up.
Eventually, the new growth rings will add plenty of strength to the tree, and after
a few years it’ll hardly even be noticed.
But inside the trunk, that cavity will still remain, forever.
So with all of this in mind, I think we’re finally prepared to address the question,
does collecting maple sap hurt the tree?
And honestly, I think the answer is a pretty definitive yes.
But luckily, it’s also usually an injury that the tree can readily recover from.
And that’s why it’s so important to follow some basic precautions, like using a clean
sharp drill bit, not drilling the holes too deep, and using smaller diameter spiles when possible.
Plus you should also space new holes at least 6 inches away from previous ones, and make
sure that your tree is even large enough to support tap holes in the first place.
Because when done properly, a maple tree can be tapped yearly for decades.
But if done carelessly, it can result in irreparable damage and even death of the entire plant.
So while we’ll continue tapping the maple trees on our property, now that we know more
about the true impacts, I think we’ll also do so a little less frivolously in the future.
But in the meantime, thanks for watching.
And we’ll see you soon.