Monday, April 5, 2021
Doctoral student David Moore has been monitoring sap flow in several species of native, deciduous hardwoods during winter dormancy.

Doctoral student David Moore has been monitoring sap flow in several species of native, deciduous hardwoods during winter dormancy.

What makes certain trees candidates for syrup production and others not?
Trees are good candidates if:
- They are found commonly in the area.
- They are deciduous (we know that maples yield 'buddy' sap when the leaves come out).
- They are diffuse-porous. Ring-porous trees form new vessels (cells that transport water in the xylem) before their leaves come out, and diffuse-porous trees form new vessels after leaves come out. This means that diffuse-porous trees need to use vessels from previous years' growth to transport water to the leaves in the early spring. If there was a drought during the previous year and vessels contain air bubbles, water transport can't happen. Diffuse-porous trees, therefore, may have mechanisms to repair embolisms and to refill vessels with water (or sap) during the dormant period. Ring-porous trees may not need to repair embolisms since they have brand new vessels by the time the leaves have flushed. Diffuse-porous trees like maples and birches refill embolized vessels during the dormant season, and it's this process that allows sugarmakers to harvest sap from them.

Why do different trees' sap runs occur at different times of the dormant period?
Sap flows in maples and birches during the winter due to different mechanisms. In maples, freezing and thawing is what drives sap flow, and in birches, root pressure and starch-to-sugar hydrolysis (which happens largely after maple sugaring season) is what drives sap flow. 

Could the different seasonality of flow allow for extending the production season?
Yes! The only catch is that the scale of production may be different. If you're tapping thousands of maple trees but only a hundred birch trees, you might not be able to use the same equipment for both because the scale is so different. 

Is it worth removing beech, basswoods, and other species from your sugarbush if you can produce syrup from them? What are the economic gains or losses from doing that?
We aren't sure yet. Non-maple syrup sells for substantially higher prices than maple syrup does, so it might be worth it. There is also the capital expense of setting up your sugarbush for an entirely new species. 

Does tapping make trees cause them harm in the long-run, or make them more vulnerable for pathogens, pests, or even long-term issues such as climate change?
Tapping trees does wound trees and allow for pathogens to get into the sapwood. Healthy mature maples that meet tapping guidelines are vigorous enough that this wounding is not detrimental. In fact, a study from UVM found that trees generally put on more than enough girth growth each year to make up for the tissue lost to the tap hole wound.

If sap flow increases after the heating cycle, could removing other trees near the sap trees allow more heating and better flow after sunset?
When you have solar radiation, it does increase the heat and you can get greater temperature gradients. Even when the temperature isn't quite above freezing but the sun beating down, you can still get a thaw that benefits the sap flow. That’s one of the benefits of thinning your sugar bush.

When coniferous trees are removed from around sugar bush to allow for that light, that also gets rid of the squirrels that chew on the sap lines. With my sugar bush, I'm trying to keep it as cold as possible because I want to keep the season going longer. Usually cold is not the issue; it gets too hot too quickly. But there are multiple benefits of thinning. 

If you are using different trees like sycamore or birch, what age do they have to be? Are there different advantages to using younger or older trees? 
People in very northern latitudes tap much smaller birch trees. They don’t have many trees, and birch is a short-lived species. The real issue is when you tap a tree, you inflict a small wound on it. For the sugaring to be sustainable, the tree needs to make that amount of growth up during the growing season. If you follow maple tapping guidelines and you're tapping healthy mature trees, then you’re easily meeting that. The wound response for birch is a little bit worse than maple. They are a little worse at compartmentalize their wounds so you may want to be a little bit more conservative with birch. 

Is there a minimum number of trees needed to produce enough sap and syrup for maintaining a particular operation? 
In a good year for me, out of 250 taps, a good year for me was producing five gallons of birch syrup. I would collect 100 to 150 gallons of sap a day and you need the equipment to process that, but you end up with a lot less syrup. The good news is that birch syrup sells for at least four to five times more than maple syrup. You can certainly turn a profit on it. You are going to make a lot less syrup with birch trees because the season is shorter—two to three weeks instead of six to eight weeks—and the sap is more dilute. But the tap yield per day is about the same as maple syrup so you need to stay on top of it. 

For folks who are already making maple syrup, they know their profit margins and how much they are making on average on an annual basis. If you use the data about sap yield—the amount of sap you get during the season—and factor how much more birch sap you'll need, you can figure out how many taps you need to produce the amount of birch syrup you want. 

What are the market opportunities for specialty syrups? Is there demand for these different varieties? 
There is much more awareness about specialty syrups now. Twenty years ago, there were no birch syrup producers in New England, and now there are about half a dozen. Depending on your location and public awareness, it can be very easy to sell out quickly. There are not many people making these syrups right now in the state. Many don't want to be the first to jump in. In New Hampshire, we have twice as many beech trees as we do maple trees. There is a lot of potential for these syrups. People who produce birch syrup need to find local markets. Bartenders are interested in using them for mixed drinks and chefs in local, high-end restaurants. Someone who is very creative could market syrups based on flavors and taste notes.

Do the specialty syrups taste distinctly different from each other? Can you describe how they differ?
With birch syrup, taste really depends on the processing. The taste can range from kind of smoky and burnt from tasting very sweet, a little bit lighter, a little more raspberry-ish. In general, I would say molasses and maybe just a hint of miso is how I would describe it. Beech is a lot like maple. Walnut is a lot like maple, but maybe a little smoother and nutty. Sycamore is very different. It tastes almost like honey or butterscotch. 

I’ve had birch syrup that tastes like molasses. I’ve had birch sap that was concentrated to about 6 to 8 percent sugar content that was not boiled and had that wintergreen taste to it, which was fabulous. That has a lot of potential, especially if you let it sweeten up a little bit, but not boil it. It’s a blank canvas right now. 

I actually like birch syrup more than maple syrup. It’s a stronger flavor and not quite as sweet. It takes some getting used to, but I found it to be really pleasant. 

How much does it cost to produce these novel syrups, and how much can you sell them for?
There hasn't been any work on production costs yet. The sap-to-syrup ratio for non-maple syrups is generally much higher than it is for maple syrup. Birch syrup typically sells for at least 4 or 5 times more than maple syrup sells for.

What are the marketing opportunities for value-added products made of syrup like candy and soda? 
Maple syrup is primarily sucrose, which is table sugar. Birch is very different. It is primarily fructose and glucose, which are monosaccharides not disaccharides. I don’t know how well birch syrup would work for candy. Certainly, birch syrup is popular with the beverage industry.

The other value-added product that is popular in Eastern Europe and Scandinavia is making probiotics with the sap. I haven’t seen probiotics made from sap in America and this is a potential niche market that could be explored. We also will be doing blind taste tests to get an idea of people’s taste preferences for these different syrups and their willingness to pay. 

How do you find customers who are willing to buy these different syrups? What is the market for these specialty syrups and, if it’s small, how do you build markets for different syrups?
Health food stores, specialty grocery stores, and restaurants that specialize in local foods will likely be interested. Giving out samples at grocery stores and farmers markets is a great way to get the word out, but that takes quite a bit of work. The media has been helpful in generating interest recently. Having a good, accessible, well-laid-out website is very helpful.

Are you doing any kind of sensory analysis for the flavors as well? With potentially different uses of these syrups in baking or cooking, how does the flavor analysis change potentially in the different applications? 
I'm hoping that we can team up with a couple local chefs who would do a much better job answering that. 

Where can we purchase (or taste) some of these syrups?
If you do a quick internet search for “birch syrup” you will find many producers that you can buy birch syrup from online. Walnut syrup can be purchased Simple Gourmet Syrups  and Tonoloway Farm. New Leaf Tree Syrups sells beech syrup.

For more information, contact David Moore at