Well, our birches started producing this week. We are a bit early, but we were nervous about missing the season. For the last five days, we have collected between 1/2 and 1 gallon of sap from each tree and boiled it down on our stovetop. It boiled down quite rapidly--within an hour or two our soup pot had just a trace of brown syrup covering the bottom. We were very unscientific about the process--no candy thermometers or grading going on here. But we now have about 3/4 of a cup of birch syrup in our fridge.
The verdict: yum! Although our taste buds are honed for the maple flavor, birch syrup is still quite good. It smells like a good day in the garden in early spring. My favorite new edible so far, and the sap boiling makes the house smell great!