Frozen ground and sap flow.

[DrTimPerkins]

Yes, the recharge occurs with a refreeze (anytime...doesn't have to be at night). During exudation under gravity conditions, sap flow will slow down a lot when the temperature drops off a high point. This is due to gas bubble expansion/contraction due to temperature changes. As the stem gets hotter, gas bubbles expand and sap is pushed out (kind of like squeezing a sponge). If the temperature drops after that point, gas bubbles contract (so the "squeeze" is relieved) and sap flow slows down or stops. You may get a weeping flow after that, but not much until it either A) recharges due to a freeze or B) the temperature gets higher than the previous high (to give it a little harder "squeeze"). With a recharge, you could get a good flow. With just a new high temperature, you will get some flow, but it'll be slow to moderate at best.

[billschi]

In your opinion, does this forecast look promising or are the daytime temps too high?
Screenshot_2018-04-22-10-24-01.jpg

[warners point]

I went out to the sugarbush and tried to drive a stake into the ground. Didn't even make it one inch. I'm guessing that most of our sap we collected, which was only 275 gallons on 160 taps was stored in the trees last fall. Will the trees run at all even if you don't get a "recharge" from a freeze/thaw? Do the trees take up any sap once the roots are thawed but the weather won't cooperate?

[billschi]

I was wondering the same thing. Isn't sap needed for the leaves to come out?

[markcasper]

I was wondering the same thing. Isn't sap needed for the leaves to come out?

Know what your saying, but why doesn't an oak, or many other species "run" sap then?

[regor0]

Most of roots would be below frost line.

[warners point]

Most of roots would be below frost line.

Actually maples have a very shallow root system.

[North!]

Still waiting on the frost to disappear. Very warm temperatures on the north shore have done very little to free it up. We are bringing in some sap, and are making dark syrup, a couple hundred gallons a day. Every day we get a bit more syrup so conditions are improving. These situations are quite aggravating for I have a neighbor who rarely gets deep frost and goes like crazy once it warms up while I wait. We have another frost tonight so maybe today will be the day. I see we have one more very warm day ahead then some more normal sap weather as the week progresses. Keeping my fingers crossed.

[DrTimPerkins]

Know what your saying, but why doesn't an oak, or many other species "run" sap then?

There are several reasons, but the primary one is that most other trees have liquid-filled lumen (spaces) inside their wood fiber cells. They also have much lower sap sugar levels than maples.

Different trees have evolved different mechanisms to cope with embolisms (gas bubbles) in their xylem vessels. If there are bubbles in the plumbing, trees are unable to move water efficiently (gases expand a lot when under vacuum, liquid doesn't). Bubbles happen due to dissolved gases coming out of solution (sap) during cold temperatures. Some trees (oaks and other ring-porous species) just build new big vessels each year. These can move a LOT of water fast, but are very sensitive to cavitation (bubble formation). Others, create stem pressure (maples) or root pressure (birches) to re-dissolve any bubbles that might have formed in order to re-establish their water columns. Conifers do other things.

The sugar is important (in maples and birches) in order to create some osmotic pressure and get the system kick-started in a way. Maples without sugar in the sap (or with other types of sugars that are less osmotically active than sucrose) don't function well in terms of sap flow.

Some species...like beech, has some sugar in the sap, and a tiny amount of pressure, but you won't get much from a wound in the stem in the spring.

Different types of trees...different approaches to the same problem (embolism). End result is some are more resistant to drought than others, and some are more resistant to cold temperatures than others. But they all have to move water (transpiration) somehow to allow photosynthesis to happen.

[markcasper]

There are several reasons, but the primary one is that most other trees have liquid-filled lumen (spaces) inside their wood fiber cells. They also have much lower sap sugar levels than maples.

Different trees have evolved different mechanisms to cope with embolisms (gas bubbles) in their xylem vessels. If there are bubbles in the plumbing, trees are unable to move water efficiently (gases expand a lot when under vacuum, liquid doesn't). Bubbles happen due to dissolved gases coming out of solution (sap) during cold temperatures. Some trees (oaks and other ring-porous species) just build new big vessels each year. These can move a LOT of water fast, but are very sensitive to cavitation (bubble formation). Others, create stem pressure (maples) or root pressure (birches) to re-dissolve any bubbles that might have formed in order to re-establish their water columns. Conifers do other things.

The sugar is important (in maples and birches) in order to create some osmotic pressure and get the system kick-started in a way. Maples without sugar in the sap (or with other types of sugars that are less osmotically active than sucrose) don't function well in terms of sap flow.

Some species...like beech, has some sugar in the sap, and a tiny amount of pressure, but you won't get much from a wound in the stem in the spring.

Different types of trees...different approaches to the same problem (embolism). End result is some are more resistant to drought than others, and some are more resistant to cold temperatures than others. But they all have to move water (transpiration) somehow to allow photosynthesis to happen.

Thanks for the great information!