Saturday, March 23, 2013

Tapping Birch: Collecting birch sap for mineral water, wine, beer, vinegar and syrup

The Sap is Rising
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Collecting birch sap for mineral water, wine, beer, vinegar and syrup

23rd March 2012. 6.30am, 0 °C brrrrrrr!

 I’ve a confession: although my long-standing interest in wild food cookery does add incredibly wild and nutritious versatility to my daily menu with respect to rich soups, unique salad combinations and intriguing side vegetables – all very health promoting and worthy; truth be told, I’m actually somewhat of a sugar addict. Yet, for the most part, sweet wild foods are associated with the abundant fruitfulness of summer and autumn – apples, pears, cherries, blackberries, bilberries, mulberries etc, and as delicious as such fruits are in their unprocessed state or as fruit leathers, their sweetness is invariably counterbalanced by varying degrees of acidity. Hardcore, unadulterated and non-toxic sweetness is actually quite hard to come by in the natural world, at least where I live.

Yet, from as early as the final week of February (Southern England) until as late as the end of April (Scotland), and with a similar early to later coming of the spring across the different states of the US, that hardcore sweetness lies quite literally in untapped abundance, residing in diluted form within the trunks of some of our commonest trees: Birch (Betula species), Lime (Tilia species), Sycamore (Acer species), Walnut and various others. All, in theory, can be successfully tapped for their sap, the first two providing the best results in my experience. Birch, especially, is fail safe!. Indeed, on the basis of research and reports of success in this regard, I’ve tried to tap both walnut and sycamore for sap from February to April for the past 7 years, but without success. This year I intend to try our only UK native maple for the first time: The Field Maple (Acer campestre). For the purpose of this article then, ‘sap’ refers to birch sap only.

But why bother doing this? This is a question I'm frequently asked, quite often by people who have tried and have been disappointed that what drips from the tree tastes pretty much like water, not the sweet ambrosial nectar they had expected. Well, it's a reasonable question I suppose. There are many answers. In the Ukraine and parts of Russia the sap is collected and sold as a type of mineral water, so they clearly value it. A fantastic, easy to make and reliable white wine can be made with a very distinct and pleasant taste, as well as beer, vinegar (see recipe at the end) and a rich caramel and molasses-like syrup. But, above all else, as with all foraging, it provides an excuse and opportunity to arrange your life according to the cycles of nature rather than the oppressive dictates of work routines and the terrible tick-tock tyranny of clock time or even traditional calendars. Each year I try to refine my understanding of when the sap flow begins and when it's in full swing. This year it begun a day before the spring equinox, 5 days after reports that frogspawn was appearing in local ponds, and two days before the wood ants began to awake from winter slumber as they amassed to form new colonies. This is the realm of magic, awareness, and attunement, connecting with life, poetry and mystery and clocks serve no purpose!

The sap then, which is actually about 95% + water, minerals and a little sugar, can be evapourated off to make a sublimely delicious if somewhat energy intensive syrup – it is the absolutely perfect accompaniment to elderflower fritters. In fact, the only near equivalent you can buy in this country is maple syrup. That is commercially viable because the ratio of sap required for a litre of syrup is 30:1, whereas for birch it is between 80 and 120:1 (I usually find that a 95:1 ratio is perfect). But don’t let that put you off. Once you’ve tasted birch sap syrup, the effort required to make it will seem more than worthwhile. For those who are unconvinced there are several other excellent uses for the sap once collected as I shall explain below, as well as various birch-related bushcraft skills to practice while the sap is simmering. First, though, how exactly is it obtained?

There are several possible collection methods; here are just a couple. Between the end of Feb and mid-April when temperatures are usually between 0 and 15 °C – but especially in the second half of March, take a metre length of 0.5-1cm diametre plastic tubing, a 2 or 4 litre plastic bottle (keep spare tops to put on the bottles when returning to pick up the sap - or just return with a large container), a drill with drill bit the same diametre as the plastic tubing, a piece of tissue or cotton wool, a lump of plasticine (modeling clay) or natural clay, a wooden bung and a hammer. Select a suitably sized and well-established tree – at least 8-10 inches across. Also, especially if in a woodland with lots of birch competing for space and light, go for the trees with the largest crown of branches. These will have the best sap flow. Mark a spot 2-3 feet up from the tree’s base. (In fact, you can tape a collecting vessel to the main trunk 15 foot up the tree if you don’t want it to be disturbed – useful if the trees are in an urban environment where your collection set-up might be tampered with lower down).

With the drill bit angled about 30 ˚ up from the horizontal (although straight in is fine too), drill a clean hole about 3-4 cms deep into the tree (however, see text in red below). Blow out bits of debris (close your eyes!). Liquid should drip from the hole within 10-20 seconds at the rate of 4 or more drops per second at the peak of sap flow. If not, hammer in a wooden bung or piece of clay and try another tree. Push one end of the plastic tubing 1-2 cms into the hole so that it is held firmly in place. Place the other end into the collecting bottle, far enough in so that it can’t slip out. Gently pack tissue or cotton wool around the tube at the neck end of the bottle, allowing the air to escape as the bottle fills with sap and to prevent insects from getting in (you can just cut or melt holes into the top of plastic lids – but make sure it isn’t a completely tight fit as you need to allow air to escape from the bottle as it fills up). Scoop out a handful or two of soil at the base of the tree and place the bottle in the shallow hole created to prevent it falling over. As a precaution, to prevent any leakage, you can roll out and press a small piece of plasticine or clay around the tube to make a perfect seal with the tree trunk. Leave for 12-48 hours, after which time the bottle will most likely be brimming with sap. Alternatively, you can use a small length of tubing or a small elder stick after clearing out the soft central pith, and allow the sap to drip freely into a collecting vessel such as a demijohn – preferably using a muslin covered funnel to direct the liquid and prevent insects falling in (or use a maple tap). In woods where there are wood ants, the ants will amass around any exposed sap. Finally, plug up the hole to prevent infection of the tree, particularly from fungal spores. Hammer in a hard wood bung, firm piece of cork cut to size, some clay or, as a temporary measure, a piece of plasticine. Whatever I use, I always line it with fresh cherry resin. Resin production is a tree’s healing response to mechanical damage so is worth using. It also makes for a really good seal. I take no more than about 4 litres per tree, and only tap the same tree on alternate years. Nevertheless, some people will tap continuously from one tree throughout its entire period of sap flow, but only return to that tree every 4-5 years; others take 2 litres and return every year to the same trees.

A great drill, but often hard to see when I put it down among the forest floor leaves!

The method I use described below is the one I find works best for me in terms of efficiency, and is born, in large part, out of trying to do minimal damage to the tree. Do bear in mind though that there are alternate views. I spoke to my friend Miles Irving (of Forager Handbook fame - a great book) the other day; he is new to birch tapping so we went out and got to work. Later he spoke for an hour to the chap who supplies the now world famous Copenhagen restaurant, Noma, with birch sap. He taps birch in Norway, drilling half way into the tree, tapping the same trees through out there sapping season. He also believes that blocking up the holes afterwards is actually more likely to lead to infection than leaving them exposed. I think sealing the hole creates a good physical barrier to the entry of fungal spores and other possible agents of infection. The alternative view is that, left to its own devices, the trees will actively produce more antifungal and other protective substances around the damaged tissue, and that blocking the hole slows down that natural process. An interesting idea I’ll investigate further and update here.

When I first tapped trees 15 or so years ago I did try drilling much further in, sometimes as far as half way in, but found no increase in the speed and volume of sap collection. A good test would be to drill half way into one side of the tree, fitting tube and collection vessel, and only an inch the other side, as I usually do, setting collection equipment in the same way. I shall try this next week. Okay. I did this test on 4 trees on 12th April. On each tree I drilled in my usualy way - just a couple of cms, AND drilled a separate hole going right to the heart wood. On all 4 trees, the containers connected to the heart wood tapping hole produces 3x the sap volume of the other one in the same amount of time.

But, really, to answer the question I’m frequently asked: Does tapping damage the tree? Well, of course, drilling a hole into a tree is damage, but let’s not forget, as indicated above, birch are resilient, with natural healing mechanisms that activate to heal such damage. Four years ago my friend had tree surgeons cut many large branches from the silver birch in his garden at the peak of sap flow. Sap rained down for two weeks. Today the tree is strong and healthy. On the other hand, you may make one small hole to tap a tree and decide not to plug it afterwards. Now, perhaps due to drought or other environmental conditions that tree has been severely stressed for a number of years. Normally its own defences would help fight infections, but now when the spores of birch polypore or some other fungi enter the exposed hole, they don’t encounter the usual resistance, sprout and infect the tree, ultimately killing it (or at least speeding it on to its next level of existence as food for the forest). So there is no simple answer, other than try to be sensitive and aware of when it is and when it isn't appropriate to tap.

Unless you intend to use the sap for cooking or drinking immediately, refrigerate and use within 2-3 days. If you decide to tap one tree throughout its sap rise, empty out the collecting bottle within 48 hours (at the latest - after 24 hrs if the temp is above 10 °C) of tapping or when your collecting bottle is full – whichever occurs first. If you leave the container over 2 days before collecting, the natural yeasts present may already have stated to ferment the sap, using up what little sugar there is, giving rise to off flavours - these become intensified when reduced down during syrup production and are to be avoided. Note: if you want to transport large quantities of sap, I recommend scrounging several of those large 18 L capacity mineral water bottles seen in offices. These are also excellent for wine making.

Boil the sap until it is thick and dark, barely simmering at the final stages to prevent the disaster of burning. Indeed, at the latter stages the pan should be just on hot embers – no direct flame). Indeed, once the volume of sap is reduced from 95 to about 5 litres, I usually transfer  the syrup to a new pan and place indoors on the hob at the lowest flame setting - not even simmering. Also, unless you want to deep steam clean your kitchen or make the wallpaper peel off, this is definitely a job to do most of outside. Alternatively, ask a friendly baker if you can place a large metal tray of sap on top of his bread oven to slowly evaporate. Taste repeatedly as you concentrate the sap to reach your required degree of sweetness. It is inevitable that the sugars will partially caramelize, that however is just an integral part of the flavour (in the absence of expensive industrial machinery to produce the syrup using reverse osmosis). If concerned about burning there is no need to reduce 95 L sap to 1 L of syrup. The ratio of 50:1 also makes for a gorgeous but lighter and runnier golden brown syrup.

Evapourating off the water and removing scum.

It can take 4-5 hours or more to make a litre of syrup. That time, however, presents a real opportunity. You can collect birch bark for fire lighting, collect birch polypores for making razor strops, paper, shoes or, best of all, you can make birch tar. I did this last year following talented bushcrafter Jonathan Ridgeon’s excellent online tutorial:

Or how about collecting some bark and making a simple birch bark and spruce root basket: Perfect for collecting the stunningly impressive Scarlet Elfcup fungi that are still in season now.

Nevertheless, if syrup making still seems too much trouble use the sap to make a lovely refreshing wine instead. It’s easy and is definitely not a second best alternative. Start by making a high alcohol tolerant wine yeast starter culture. For this, simply follow the instructions on a packet of wine yeast – usually this involves adding a teaspoon of yeast and sugar to about 3 fl oz of boiled and cooled water that is then shaking in a clean sterilized bottle. The top is loosely fitted on and the bottle left in a warm place for about four hours or until the yeast becomes active – you’ll notice bubbles rising and a little froth forming on top. Next, sterilize 2 demijohns, 2 rubber bungs, 2 air-locks and 1 plastic funnel – the products used for cleaning babies’ bottles are fine for this purpose. Put 8 pints of sap and 1kg of sugar into a large pan and bring to the boil stirring in all the sugar. Add the juice of 1 lemon and 1 teaspoon of yeast nutrient. Empty and rinse the sterilized demijohns with boiled (but cooled slightly) water. Divide the sap equally between the 2 demijohns, pouring in using the sterilized plastic funnel. Allow to become luke warm before adding the yeast starter culture and fit bungs and air-locks. Leave in an airing cupboard for 5 days before transferring all the sap into just one of the demijohns. Ferment until no bubbles appear in the air-lock (2-3 months).

Birch sap wine in demijohn and glass.
Spoons showing commercially produced
maple syrup (left) and birch syrup (right).

If you're feeling both naughty and adventurous you could also get hold of an old-style basic pressure cooker, a siphoning tube, a bucket of cold water and a demijohn to distill your birch sap wine to make birch sap moonshine. That could then be used for Russian-style preservation of gorgeous chanterelle fungi, gathered from around the same birch trees you have tapped. Of course, it would be illegal so I must advise against it. I just said "you could", not "you should".

Chanterelles preserved in alcohol

Finally, you’ve decided you’d like to try out some of the suggestions above but, it’s 1st April, you’ve drilled a hole and are standing there feeling like a true April fool because not a drop of sap is flowing out. Don’t worry, the sap rise is over. The leaf buds are swollen and bursting into life. Excellent! The young tender leaves are good for tea (would be a good experiment to ferment them in the way true tea leaves are) and excellent as a mild bulk salad leaf. But don’t miss this opportunity either as the leaves only stay tender for about 2 weeks!

Birch Sap Balsamic Vinegar Recipe

(Linfa di betulla aceto balsamico non tradizionale)

2 litre capacity vinegar aging barrel

Ingredients (makes  approx1.5 L)
190 L fresh birch sap
1 sachet high alcohol tolerant wine yeast

MethodBoil the birch sap down to 4 L. Place half of this i.e. 2 L into a sauce pan and carefully (on lowish heat) very gently simmer, reducing down to 1 litre. Pour half of this into a wooden barrel and leave for 4 months; pour the other half into a sterilized glass bottle and seal. Place the other 2 L in a sterilized 1 gallon demijohn. When warm or cooled sprinkle on the yeast (or use wild yeast cultures if desired). Fit an air lock, place in a warm cupboard, and ferment until no bubbles appear in the air lock (approx 4 months). Uncover and expose to the air and fruit flies for a few days. Then cover with muslin and allow to turn to vinegar. This takes about 2 months. Pour vinegar into wooden barrel to add to the syrup already in there. Age for 25 years, transferring the vinegar to a smaller barrel of a different and suitable wood variety every 5 years. Finally, ballance the sweetness and acidity by adding some of the bottled and pasturised syrup..

Confession (you probably realize this already!): I've not done this, at least not completely. I have followed this recipe and aged the vinegar for 3 years. I've also experimented by just letting pure sap ferment (I say 'experiment', but actually it was a mistake as I'd not sterilized the bottles well enough. But, of course, there are no mistakes! It made me realize that it was worth exploring as vinegar and, in particular, a balsamic style vinegar). The flavour of that spontaneously fermented sap is different from wine that has been turned to vinegar, hence the different stages in the recipe. This recipe is the nearest I've managed to get to something approximating balsamic vinegar using only wild ingredients. It tastes good, but would be fun to age some for the length that Aceto Balsamico Tradizionale is aged............

One final thought............

Do keep your eyes peeled for Birch Polypore fungi, also known as Razor Strop Fungi, as you are bound to come across them when you're out looking for suitable birch trees to tap. These can be found on dead standing trees or on toppled trunks and fallen branches. Of course you can make razor or knife strops with these, but far more fun in my opinion is to use them to make paper. Be careful not to have the fungi knocking about in your bag with your drill. It will get contaminated with spores and you may end up infecting previously healthy trees!

A good crop of Piptoporus betulinus

Top side

Underside showing the pores

The other day I collected a whole sac full of these. I dried them for future use in The Foraged Book Project for making paper for that book, scraping off the brown outer layer once they were dry.

Dried, scaped and vacuum sealed Birch Polypore

Many other common rubbery textured fungi can be used to make paper too. Here's some basic information on how to do it:

Have fun out there!



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At 9:42 PM, Blogger mousiemarc said...

That is really cool. I live in oregon in the united states. Doubt I'll get to this anytime soon with two young ones. But it looks really fun.

At 8:03 AM, Blogger velvetkatze said...

Wow, this brings me back to my childhood - it used to be very popular in Russia and was sold in 3L jars in the shops... Loved it!

At 8:09 AM, Blogger velvetkatze said...

I like your blog a lot, but I cannot find a way of following your new posts - usually you can submit your email somewhere on the blog and it sends you automatic updates when something new comes up, but I cannot find how to do it on yours - can you give me a hint please? Thanks

At 5:32 AM, Blogger Fergus said...

@mousiemarc. Don't let two young ones stop you. I actuallu initially set up all the bottles on 17 trees with my friend. He had his 3 month old baby on his back in a pouch and his 4 year old daughter helped me drill and seal the holes while asking lots of questions!
@velvetkatze. Was that 3L of sap or syrup?
I wish I knew how to set up automatic updates, unfortunately I only ever know how to do the most basic stuff on blogs and whatnot.....

At 2:16 AM, Blogger Unknown said...

Another inspirational and detailed post. Thanks! I missed the boat this year but will keep my eyes peeled for suitable trees to do next time.

At 12:55 AM, Anonymous Anonymous said...

Thanks for a super article! Not quite as cool as tapping your own tree, but perhaps more convenient - Byarozavik birch tree water, USDA and Euroleaf organic, bottled at the the source from hand-harvested pristine forests in Eastern Europe. or purchase at

At 4:13 AM, Anonymous Marco Colli said...


I've read with interest your article. I have to say that this is the first year that I'm trying to collect birch sap. And since I'm a beginner and here's in Italy no one has ever collected birch sap before I have some doubts.

In particular, do you always get a crystal clear sap or a very slight white color is acceptable? Because even when I collect sap every 12 hours it is not perfectly clear. Only at the beginning of season (for a few days) I managed to get crystal clear sap. Now, even with newly tapped trees (drilled 5 days ago, but the sap is collected frequently), it's non perfect - maybe due to the warm temperatures (18 °C during the day, lower at night). Here's a photo comparing water (on the left) and sap on the right:

Thank you very much!

At 4:01 AM, Blogger KevB said...

Great article, but there's no u in evaporate! ;-)

At 7:00 AM, Blogger Unknown said...

Absolutely fascinating

At 4:18 AM, Anonymous Yetty said...

Great post :)

At 12:57 PM, Anonymous Anonymous said...

Thanks for sharing such a good idea, post is fastidious, thats why i have read it entirely


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