How many taps per tree

[Fraziert]

I am fairly new to this forum, and new to sugaring. I attended a Bascum maple seminar last October and one thing that resonated with me was how atmospheric pressure changes affect the sap run and the more leaks in the tree the less pressure it can generate, "so be careful about adding that second tap. Only use 2 taps for really big trees. Never 3 taps." Well I really took this to heart this year and only used 2 taps on trees that were well over 30 inches in diam. As I have now had many hours sitting alone boiling and many more waiting for the sap to run, I am wondering what others think about this "loss of pressure with each additional hole".

If the channels that carry the sap in the trees run vertically, from the roots to the branches, it would seem that one hole is independent of another on the other side wouldn't it? The tree doesn't have a centralized pressure system like a human body, relying on a heart to pump. So I'm thinking I may have undertapped by leaving those 20" trees with just one tap. Thoughts?:confused:

[DrTimPerkins]

it would seem that one hole is independent of another on the other side wouldn't it?

Not entirely.

The easiest way to conceptualize this is to think of a large pipe that is stuck in the ground upright. Inside the large pipe are millions of very small diameter, fairly short straws. The connection between any two straws that are end-to-end is not perfect....there is some leakage between those connections, however if you tried to move water through the entire assembly, the vast majority of water would have a tendency to move vertically (up and down).

Now full the entire pipe and small straws with water. Then drill a hole in the bottom of the pipe. Water will flow out from the hole fairly quickly at first as the straws that were cut by your drill bit empty from above. Over time as the head pressure drops, the flow rate will also drop off as straws near the drilled hole empty. Eventually the flow rate will get to be fairly low (weeping flow), but not zero as straws on the other side of the tree contribute some sap to the hole. Near the end you will still find some straws far away from the drilled hole are still full because the resistance to flow across the straws is higher than the head pressure above those straws. If you put a second hole in that tree on the opposite side, you'd get a good flow rate (not as good as your initial hole, but still more than a weeping flow), and it would drop off again. The end result is that while you won't get 2X the sap from 2 holes in a large tree, you'll get fairly close to that (depending upon the size of the stem). This is under gravity conditions.

Under vacuum conditions, we can pull the water from areas that are further away in the tree through those imperfect straw-to-straw connections, as well as pull sap upward (from below the taphole). In all but the largest trees, you definitely won't get anywhere close to 2X the amount of sap....it will be lower than that due to this horizontal movement of sap across the stem, and the difference will be proportional to the tree size and the vacuum level you pull. So the diameter at which to put a second tap in a tree under vacuum should be higher than that for gravity trees.

You might want to read http://www.uvm.edu/~pmrc/One%20or%20Two%20Tapholes%20-%20Wilmot.pdf for more information.

However in all of this, it is important to realize that a taphole is a wound, and the growth of the tree must be able to sustain the repeated wounding by tapping. By putting in a second tap you must have growth rates good enough to avoid a build up of compartments (stained, non-functional wood), which will decrease your sap yield and affect tree health.

[Fraziert]

Wow, that was a great explanation of a complex process. Thank you so much for taking the time to educate me. There really is a lot more to it than I first thought. I feel much more informed now and able to make better deicsions about adding that second tap.

[Dave Lister]

What would you do when one large diameter tree splits off and becomes two good sized trees a few feet from the ground(within tapping height)?
Do you tap just one of the two trees every year, alternating which tree gets the tap year to year, or would you put a tap on each one, considering each to be its own tree, even though they both share the same trunk and root system?

[AndrewsofBow]

How does squirrel damage effect this? I have branches up high that are weeping sap, some very long sapcycles.

[DrTimPerkins]

What would you do when one large diameter tree splits off and becomes two good sized trees a few feet from the ground(within tapping height)?

As long as they split below the height where you would tap, then typically each stem would be considered a separate unit.

[DrTimPerkins]

How does squirrel damage effect this? I have branches up high that are weeping sap, some very long sapcycles.

You will lose some amount of sap, but the loss of head pressure from broken or wounded branches high in the top of the tree has little effect. Again, going to the "pipe model" described below, if you have that pipe stuck in the ground and you create a hole near the top, as small amount of sap will run out then quickly stop as head pressure diminishes. However if you put a hole lower down on the pipe, you'll get more sap out of it. Under gravity (and to a large extent the same thing happens under vacuum), it is all about the difference in pressure from the top of the tree to the taphole.

[TerryEspo]

Great information, just learned something.
Good idea to keep this post alive and up on top so some others may gain this knowledge.

Thanks Tim.

[KevinS]

Good stuff thanks.

[Pauly V]

great information. Thank You