Friday, March 6, 2015

Birch- Maple's sappy boyfriend

Our warm winter has not been good for Bigleaf Maple (Acer macrophyllum) sap production in Bellingham. There were some decent freezes in the late fall, but I didn’t bother tapping. In the past, the early season flow has been poor and the interval between cold spells, long enough that the taps healed over and the equipment needed to be washed. Sap did run the week following Christmas, but since then none of the frosts have been cold or long enough to stimulate any flow. Fortunately for me, Dad collected some maple sap just before the New Year while I was traveling for the holidays, otherwise I would have nothing to show for this year.

I didn't want to give up too easily. Last year, the majority of the runs happened in late February and early March. The weather was consistently cold, with a few storms thrown in. You might recall the Feb 23, 2014 snow storm that overloaded many tree branches. Such a “late” winter storm is not uncommon in this area. On the same day in 2011, it snowed 10” in Victoria BC; and on March 5, 2012 it snowed ½” in Bellingham. Beyond the tenure of my written records, I have numerous childhood memories of late storms shrouding crocuses with snow. These last few years’ experience have taught me that sap flows strongest during snow storms, so I wasn’t going to give up on the sap season during the balmy weeks in mid-February. I sanitized my taps, piled firewood, loaded my truck, and kept an eye on the weather.

Two weeks ago on Feb 21st, we had a frost that was heavy enough to leave ½” of ice in a pail outside, despite a low that was predicted to be several degrees above freezing. Freezing weather in Western Whatcom County is evidently hard to forecast. My theory is that we are close enough to the Fraser Valley that minor nighttime outflows of cold interior air provide us with lower temperatures than the rest of the Puget Lowlands. Despite the next nights forecast in the mid-thirties, I awoke to frost again on the 22nd, and decided to mobilize. I drilled into my first Maples around noon on a sunny day with temps in the low 50s, and the sawdust was dry. Two more Maples also yielded dry sawdust and no subsequent sap flow, so I gave up on Maples. Besides, I had noticed that a few of the buds had already burst. I think the Bigleaf Maples are truly done for the year.

But what about birches? I have heard that syrup can be made from birch sap too, and knew that they are said to run in slightly warmer temperatures. Why not try? I scouted the hillside with drill in hand and bored into the first Paper Birch I found. The saw dust was pulpy and my hole immediately started dripping sap! I rushed for supplies and after the first tap and pail were installed, located 5 more Paper Birches to tap.
In the 14 days since, I have collected 42 gallons of sap from those 6 birches at an average rate of ½ gallon per tree per day. The nighttime lows have been between 30 and 40, and the highs mostly in the 50s. Every other day I collected about 6 gallons, and reduced it to about 50 percent sugar before freezing it. With the exception of my first batch, which I was eager to taste, I waited until the end of the season to aggregated all my frozen near-syrup, and finish the syrup all at once. See my Bigleaf Maple syrup article for details on how to finish syrup.

The chemistry and concentration of birch sap is different than maple sap. Birch sap is mostly fructose and glucose, with small amounts of sucrose, whereas maple syrup is primarily sucrose with some fructose and glucose. The concentration of sugars is much lower in birch, often requiring 100-120 parts sap to produce 1 part syrup, compared to the 30-50 to 1 ratio for maples. The simpler sugars found in birch sap make it more prone to “scorching,” and for reason’s I don’t understand, the flavor of birch syrup is often described as “spicy” and “more savory than sweet.” I think the syrup tastes like roasted camas with a hint of peach. Katrina thinks it tastes like honey. 
Finishing a small batch of Paper Birch syrup

Paper Birch description
There are about a dozen species of birch in North America with the center of diversity in the Northeastern Woodlands. Only three species are native to the Pacific Northwest: Water Birch (Betula occidentalis) which grows along streams and wetlands east of the Cascades; Western Paper Birch (Betula papyrifera), which grows at low to moderate elevations west of the Cascades as well as open woods east of the Cascades; and Swamp Birch (Betula glandulosa) which grows in very wet areas, mostly in the mountains east of the Cascade crest. European White Birch (Betula pendula) is also commonly found in yards and parks throughout our area, and has very white bark and fine, drooping twigs.

Drooping twigs of European White Birch
Upright twigs of Paper Birch

Collage showing color variation in Paper Birch bark
Paper Birches are small deciduous trees that mature to heights of 40-60 ft and usually 5-12" in diameter with rare individuals growing larger than 16" wide. The trunks are occasionally clumped or multi-stemmed near the base. The horizontally peeling bark that is so characteristic of mature Birch trees takes on more color variation in our region than the white barked variety of the northwoods; grey, copper, and orange tones are also common here. The trunks of Paper Birches in the west also carry a considerable load of lichens, and mosses may cling to the base. Whatever the color or age, all the bark is covered with distinct horizontal bands of lenticels that permit gas exchange.

Paper Birch catkins
Paper Birches branches ascend at a steep angle from the trunk. In young vigorously growing trees the branches are straight, but with maturity the trunk and branches take on a more twisted form. The fine twigs have a purplish black color and usually extend upward. Catkins emerge after Red Alder but still ahead of Birch leaf-out, and are usually in clumps of 2-3 at the ends of the previous year’s growth. Leaves are alternate, simple, and have serrated margins. The trees are short lived, but die slowly. Dead tops are very common in Paper Birches, and provide important habitat for cavity nesting birds. As decay extends downward, they frequently host useful and edible fungus.
The ethnobotany of our region includes virtually no food use for Paper Birch. Further north where birches are more common, the Upper Tanana in Alaska traditionally drink Birch sap raw (Kari 1985). Eastward, other northern Peoples make birch syrup, such as the Algonquin in Quebec and the Cree in Saskatchewan (Moerman). The Cree and Montagnais also traditionally eat the bark cambium of Paper Birch (Moerman).
Where birch occurs in the Pacific Northwest, the bark is used for containers and canoes, the wood for carving, and both the wood and bark burned. Birch has many traditional medicinal uses as well. The most interesting to me is the Nlaka’pamux (Thompson) use of birch sap as a spring time cold and cough remedy (Turner et al. 1990).

Sap isn’t the only edible part of a birch. Xylitol, an artificial sweetener that has a dramatically lower glycemic index than sucrose, is produced by wet oxidation or steaming and distillation of several plant based carbohydrates, especially birch wood. I will probably have to take some chemistry before I attempt doing this on my own.

In our region, collecting sap and making syrup are novel activities that, on good years, can supply the dedicated forager with their sugar needs for the year. However, Bigleaf Maple is on the margin of climate suitability (not enough freezing days; unpredictable season), and Paper Birch is on the margin of labor efficiency (the sap is 2.5 times more diluted than maple sap), and habitat suitability (not that common in the Western Washington). Even though both species have individual limitations, I have learned this year that Maple and Birch complement each other perfectly and can ensure that at least some syrup makes it into the pantry.

The folks at  Kahiltna Birchworks in Alaska are the only commercial source of Paper Birch syrup that I can find. I have never heard of anyone tapping any of our other birches.

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  1. Hey Abe, Great articles. Euell talks about tapping the sweet birch which tastes like wintergreen and provides an abundance of sap. Keep up the good work.

  2. They make some up in Vermont too. Good stuff. I actually prefer it to maple.

  3. Great Article! I see a lot of "B.C. Yellow Birch" firewood for sale in the Okanagan region of British Columbia. I assume this isn't proper yellow birch(Betula alleghaniensis) but a Paper Birch with a yellow colour. Do you have any thoughts on that?

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