Tapping trees that have wind damage

[Hogsback Maple Syrup]

Been sugaring for awhile and with the recent storm damage to trees I would like to know the science of a tree producing sap. My question is this. I have a number of trees that have been snapped off at the top so there is a 40 foot trunk with no top branches. Since my lines are already run, can I tap that tree this year before removing the line and cutting down the tree? Is there enough sap in the walls of the trunk to get some sap since the tree will be cut next year. I realize the tree will loose its ability to produce sap in future years, but is the sap stored in the tree and roots enough to tap the tree this year?

Thanks-Hogsback maple Syrup

[BAP]

Sap storage is in roots of the trees. When sap runs, it is moving from the roots to the trunk and tops of the trees. If you know you are going to have to cut the tree, add extra taps to the tree and get what you can out of it

[DrTimPerkins]

Sap storage is in roots of the trees. When sap runs, it is moving from the roots to the trunk and tops of the trees. If you know you are going to have to cut the tree, add extra taps to the tree and get what you can out of it

Not quite.

Sugar is stored anywhere there is wood tissue, so roots, stem and branches. Water moves UP from soil into the wood during the initial part of each freeze phase during the spring. It is pulled up by a small vacuum created within the woods cells due to bubble contraction and changes in vapor pressure. The end result is that each fiber wood cell and vessel ends up with sap in it at the end of a freeze. The amount of water pulled in from the soil depends upon a couple of things, but chiefly on how fast the tree freezes. A nice slow freeze results in the best recharge. A fast freeze results in poor recharge.

When the tree thaws, if there is a hole somewhere, as the sap melts, it will typically flows (exudes) out of the hole by gravity, thus the bulk flow of sap tends to be downward. This exudation can continue for 1-3 days due to gas bubble expansion (from rising temperatures) creating pressure in the wood.

So the short version is:

- During a freeze water moves up from soil to stem (uptake).
- During a thaw sap moves down from the crown to the stem (exudation).

If you use vacuum, the story changes a bit in term of the details. Initially bulk flow is downward, but over a long sap run, as sap from above the taphole is depleted, sap flow can be from across the stem (less common on gravity) or from below the taphole. After a certain period of time, bulk flow will be almost entirely upward, and we can reach the point where water is being pulled from the soil, up through the stem, and out the taphole. At that point, producers will notice a slow drop-off in the sugar content of the sap, as the sugar in the stem is diluted by the water. It will take another freeze/thaw cycle for more sugar to be released by wood ray cells for the sap sugar content to increase again.

[johnallin]

I have a few trees that lost their tops. These sprouted new branches so thick, that they look like pine cones!!

[DrTimPerkins]

I have a few trees that lost their tops. These sprouted new branches so thick, that they look like pine cones!!

I like to think of them as lollipop trees. Straight stem, compact, bushy, round crown. Same thing happens to the saplings when we cut the tops off for sap collection. There is a single stem with a very small and very round bushy top. Maple trees can take an awful lot of abuse. The one bad thing is that the central core on these big trees that have a lot of top damage will compartmentalize, but later can rot away and become hollow. Then that tree or large branches can come down in windstorms a few decades later or when you first start to cut into it with a chainsaw.

[DrTimPerkins]

This response might actually surprise you a bit, but I would suggest that you:

1. Tap them this spring. You might not get a huge amount of sap from them (but might be pleasantly surprised). During the spring, water is drawn up into the stem during part of the freeze (uptake) phase due to pressure drop in the wood of the tree. There will obviously be less wood to store the water that is drawn up, and less sugar to mix with the water to make sap, but there is likely still enough to make it worth tapping them. During the sap exudation (flow) phase, bulk movement of sap is typically downward (due to gravity). Things get a bit more weird when you put vacuum on the tree, but by using vacuum you probably will negate some of the losses of the upper crown of the tree. A good deal of research was done after the ice storm of 1998, and (if I recall correctly) trees that suffered severe crown damage still produced good amounts of sap.

2. DON'T be in a hurry to cut them. Maple trees have a tremendous ability to regenerate lost crowns. While it is likely you will suffer some increased amount of mortality, most affected trees will recover. Entire sections of sugar woods across the northeast (Ontario, Quebec, NY, VT, NH, ME) looked like stands of telephone poles stuck in the ground. The vast majority of those trees recovered and are still producing sap. This again is from knowledge gained through research and producer experience after the 1998 ice storm. So unless you already have replacement saplings growing nearby and almost of the size to tap, I'd leave the damaged trees for a while and see what happens. Much will depend upon what type of growing seasons we end up with over the next couple of summers.

[Castlefinn]

This description of sap flow and the freeze/thaw cycle is the most clear and concise I have yet seen. Thank you!

[DrTimPerkins]

This description of sap flow and the freeze/thaw cycle is the most clear and concise I have yet seen. Thank you!

Thanks....figured it wasn't the appropriate time for the 30 page scientific version.

[whity]

Same thing happens to the saplings when we cut the tops off for sap collection.

So bag the tops and add vacuum to them! LOL

[maplecherry]

tapping dead.JPG
Tapped last year - some sap ran, dried up early. No regrowth this year.