Cold last night, warm today, tonight, tomorrow - What will happen tomorrow?

[johnpjackson]

So, it was below freezing last night and above today, and the sap is running today. It's going to stay above freezing tonight and be even warmer tomorrow.

Will we expect the sap to run overnight? Will it run tomorrow? Or will it probably taper off after dark today, and then not run again until we have another below freezing night and then above freezing day again?

Do you have a crystal ball?

I could ask my Magic 8-Ball, too :lol:

[DrTimPerkins]

Assuming you're on gravity, as long as it stays above freezing the sap will run until the pressure in the tree is equal to the pressure outside. So basically it might run for a day or two, but the flow will slow down over time. If you measured carefully you'd see that flow rate might kick up a little when the temperature went up, then slow down again as it cooled. Typically some amount of flow might last 2-3 days on gravity, but be very slow at the end. Somewhat depends on the size of your trees as well. Really big trees will flow longer as the core of the tree (and the north side) continue to thaw out. Not all sides of the tree will thaw at once.

Once it gets cold, as it freezes up the tree will pull water up from the soil to recharge the stem/branches with liquid. Transition from thawed to frozen = recharge. Frozen to thawed = sap flow (exudation).

[johnpjackson]

Thanks, Dr. Tim!