It’s also possible to harvest sap and produce syrup from hophornbeams (Ostrya spp.). Hophornbeams, or ironwoods, are in the birch family, and like birches, sap flows in hophornbeams after maple sugaring season is over. So far, very little is known about how to produce hophornbeam syrup, though conservative practices (such as using low temperatures and only plastic and stainless steel equipment) are recommended since these trees are related to birches. Hophornbeam sap contains very little sucrose and lots of fructose and glucose, so care should be taken not to process sap for too long at temperatures that are too high. Hophornbeam syrup produced without the use of reverse osmosis tastes like toffee or caramel.
As an aside, I’ve only ever tapped American hophornbeams (Ostrya virginiana) using vacuum pumps, but I’ve heard from others that these trees yield quite a bit of sap without the use of vacuum too.