Several years ago I would have thought no more about it except to view the oozing as a fortuitous feast for any early-emerging Mourning Cloak butterflies. But two years ago I wrote a post about the drinking of birch tree juice in Russia, and just last month posted a photo of a "sugar-sickle" (frozen dripping tree sap).
I couldn't pass up the opportunity. I used rubber bands to secure sandwich-sized Ziploc bags on the two clipped branches. By the time I had finished gardening that afternoon, the bag (shown above) had accumulated quite a bit of liquid, and to my surprise it was beautifully clear:
The next step, of course, was to search the internet for more information. At Naturespeak I found directions for concentrating maple sap into syrup and into maple candy (a nice article, worth a visit by those interested). The best source of information I found was at BirchBoy.com, with articles written by people in Alaska, where apparently birch juice processing is an honored pasttime:
Birch syrup is one of the few taste treats unique to Alaska and the circumpolar region. Although many people have never heard of it, birch syrup is not new. Birch trees, like many northern hardwoods, have long been tapped for their sugary, invigorating sap; but because of maple's high sugar content, generous sap flow, mellow flavor, and compliant nature, maple became the premier sugar tree in North America - except for Alaska, where birch trees are plentiful and maples are small and scarce. Birch syrup would have been the only springtime sugar source for Alaska sourdoughs in remote areas. For every gallon of birch syrup he made, the sourdough would have tapped no fewer than a hundred trees, collected more than one hundred gallons of sap, and burned nearly a cord of wood. Folklore relates that the syrup boiled down in open pans was tart, robust, and very dark, but the sourdough must have guarded and savored every drop. Neither did he have to worry much about spoilage, since pure, thick birch syrup seems incorruptible...There is an outstanding amount of information at that link on the science of birch sap and the techniques for its harvest and for protecting the trees, and the subtleties of rendering it down to a syrupy consistency.
I haven't decided yet whether to undertake that aspect of the adventure. Everything I've read suggests the process is time-consuming and needs to be undertaken with some degree of care to avoid scorching the concentrate. I have about a half-liter of fluid now, because the trees are still dripping into this third day (memo to self: in the future don't prune when the sap is running). That half-liter would be worth about 25 Euros in the Japanese market, so rather than waste it I decided to have some last night with my dinner.
I had a small glass of birch sap with my takeout Chinese food dinner last night. It tastes pretty much like very fresh water, with maybe just a subtle hint of earthy overtones. It goes well with General Tso's Chicken.