I have always used March 15th as the bench mark date for tapping trees if you use buckets. Over the last twenty years of syrup making this has been a pretty reliable date. In our operation we have made most of our syrup in the last week of March and the first week of April. Once you tap a tree, and leave an open wound the tree begins close that tap hole. When using bucket spouts, air and bacteria can also get in the tap hole and dry out and reduce sap flow. So in my experience tapping a tree means you have basically started a 3 week clock on sap flow. At the end of 3 weeks those tap holes have reduced sap flow. Tapping early in March means that you will get in on the early sap runs obviously, however, you will have reduced sap flow in the later sap runs, which in my experience have always been more productive and I want fresher tap holes for those runs. The risk is that a rapid warm up could occur and there would be no “end of season” surge of sap. Then tapping early would have been the wise thing to do.
So…… What are we going to do this year??? Well I plan to wait one more week and look at the forecast next Friday March 5. Granted this week looks pretty good temperature wise. People have reported some trees dripping and we will have 40’s for highs and 20’s for lows through next Friday. Red and Silver maples will most likely be running and they often run early, so I might be inclined to tap them this week. Following this week is a period of 3, maybe 4 days of rain/snow, and sap will most likely not run. After this period, is when I will probably tap since we have mostly sugar maples. Recall that temperatures were -25 below, about a week ago, so it will take a week of warmer weather thaw those larger trees.
I am looking at March 11-13 to tap in the St. Croix valley. The tap holes would then be 3 weeks old at April 6/7 which is typically the end of maple season.
My advice would be to watch the temperature forecasts daily and tap a couple of trees just to see what they are doing.
Be safe out there