Will the sap flow well on a rainy day?

[Tapping Wolf]

I was told that sap flow diminishes/ or even stop on rainy days....even if the temps are perfect....is this true? What has your experince been?

[Thompson's Tree Farm]

My experience is quite often just the opposite. Sap flow due to pressure differential between the tree and the atmosphere. Rainy days have lower atmospheric pressure thus there is potential for a greater difference between the internal pressure in the tree and the atmosphere. It is much more fun to gather in bright sunshine though....

[christopherh]

Last season all it did was rain, I had some pretty good runs during those periods, it didn't seem to effect anything.

[Sugarmaker]

Love rainy days! Gathered a lot of sap on those days!
Regards,
Chris

[Maple Hobo]

If your running a vaccume system, rainy days will be some of your heaviest flow days. They say vaccume can double your water collection. With rain it might be even more.

[maple flats]

Vacuum or not rain helps. Sap flows when the temps are right (below freezing then above freezing). On gravity you will often get runs lasting 36 or more hours if those temps occur, rain or not. The amount of flow is based on the pressure difference between inside the tree and outside. Rain means low pressure outside and that will often be your best flow days. When we add vacuum into the picture we are just making the the tree think the barometric pressure is lower than it really is, thus more flow. With vacuum you can often use one freeze cycle to trigger sap flow for several days rather than just the 36 or slightly more you can get on gravity. But, whichever type system you have you will find rain IS your friend.

[PapaSmiff]

I found, while using buckets to collect sap, that I still get a lot of sap on rainy days. But if the rain is dripping down the side of the tree . . . and along the outside of the spile . . . and into the bucket, the sap in the bucket can be very yellow and discolored. The rain picks up lots of stuff from the tree bark. I had to throw the discolored stuff out.

[adk1]

Interesting. I know my BIL uses the old metal lines galled the gooseneck system. when it rains, they get alot of water infiltration and at times they will pull the mainline off and let it run on the ground because its not worth boiling.

[Tapping Wolf]

Tapped yesturday morning....and had buckets over nearly flowing this morning...only one bucket was contaminated by the rain nasty auburn color, and sugar less than .5%.....the rest were clean and had 1.5%-2.2% Thanks for all the input!