Wednesday, March 16, 2011

Of Birch sap and brewing.

Last year, I decided that I'd try my luck tapping a birch tree for its sap. I'd first seen this done by Ray Mears, and subsequently by Ben Law on Hugh Fearnley-Wittingstall's a "Cook on the Wild Side".

For those who aren't familiar with the process, the Silver Birch (Betula Pendula) can be "tapped" for a very limited time in early spring. When a small hole is drilled into the trunk of the birch, the sap seeps out very quickly. The sap has about the same consistency and fluidity as water. If collected at the correct time, it is also as clear as water and tastes fairly similar.

Last year, I had little success in my initial foray into birch tree tapping. I purchased some plastic tubing, and after selecting a lone birch tree, drilled a small hole into it. Sap flowed out as soon as I drilled the hole, and I simply plugged the hole with one end of the plastic tubing, and placed the other end in a plastic bottle. I left this for the day, but when I returned, only a cupful of sap had collected in the bottle (picture below):

Disappointed, I plugged the hole in the trunk with a wooden dowel, resolving to do better in future.

Fast forward one year. This year, I was better prepared, and had created some "spouts" out of thin copper piping, cut at roughly 30 degree angle on one end, and straight on the other. The purpose of these spouts was to funnel the sap from the hole in the trunk into the plastic tubing. All that was left to do was wait for the correct time to collect the sap.

As luck would have it, several young birch trees grow in the car-park outside of the building in which I work, so I was able to check on an ongoing basis whether sap has started to rise yet. To do this I lightly drove the tip of my penknife into the bark. When sap ran down the blade, I knew to time to collect it had come.

When I next had the chance, I headed to a forest close to home, where I knew several large birch trees grew. I brought along a hand drill, penknife, the spouts and tubing, and some plastic bottles.
After selecting a suitable tree, I drilled a hole (at a slight upward angle) into the trunk, and pushed the spout into it. It worked like a charm, sap flowing down the spout with a steady "drip-drip-drip". After attaching the plastic tubing and bottle, I repeated the process with another tree.

Below are a few photos of the "tapped" trees:

I then left the bottles for twenty-four hours, and when I returned, each was full of sap. I sampled each batch - if the sap tastes "off", there is a chance the tree has a fungal infection and the sap should be discarded. However, all samples tasted fine - like a slightly sweet water. In total I collected eight litres of sap, which was plenty for the purposes I needed it for.

The next step was to ensure that the holes in the trunk were plugged, to prevent sap for weeping out, stop possible infection, and to stop insects from burrowing into the tree. With my penknife, I prepared a dowel of dry wood - tapered at one end to fit up and into the hole, and large enough at the other end to fully seal the hole I had drilled. Below is a picture of a tree being plugged:

The dowel was pushed into the hole firmly to ensure a snug fit. I then sawed the dowel off close to the trunk, as below:

With the wooden dowels firmly in, there will be no permanent damage to the trees.

Now I had my eight litres of sap, it was time to begin the process of fermenting it to a hedgerow wine. For this, I followed the instructions from the Ben Law recipe on the "River Cottage" website. Four litres of sap were added to a sterilised demijohn , and then I prepared a mixture of 150 ml of water added to the juice of a lemon, and three tablespoons of local honey dissolved into it. This was then added to the sap:

 I then prepared some brewers yeast (champagne yeast I bought at a home brew shop). This was activated by mixing it with warm water, and then it was added to the demijohn, making the liquid cloudy:

Finally, I placed the bung and airlock onto the demijohn. The process of fermentation has already begun, and the Birch Sap wine should be ready in about six months (the liquid will have to be decanted into another demijohn in a month or two to get rid of the sediment).

Overall, I was delighted with the amount of birch sap I collected this year, and the ease with which I did it. I'm tentatively calling this project a success (on the collection of sap, at any rate). The true measure of whether it was a success will be when I finally taste the wine!

More information on birch tree tapping can be found in the "River Cottage Handbook: Hedgerow" by John Wright.

There are also several videos on showing the process.