Birch Sap Drinks.

Autumnal view of silver birch with woodpecker nesting box.

Tapping into Resources.

Three magnificent mature birch trees (Betula pendula) stand in a corner of my quarter acre garden in the Scottish Highlands. One is home to a family of tree sparrows who commandeered the nesting box designed for the greater spotted woodpeckers that are regular visitors and partakers of peanuts.

A couple of years ago, on a mild April day I was working away in the bee shed sorting equipment and banging together wooden frames for holding the wax foundation that bees build up into the hexagonal cells for brood rearing and honey storage. It’s not my favourite beekeeping task but it has to be done. My attention strays often and I’m always glad of an excuse to go and make a cuppa. On the way to the house that day, the swaying birch branches caught my attention and soon I was on a mission to research tapping birch trees for thirst-quenching sap.

Where I live it’s not unusual for some country folk to tap birch trees in April as the sap rises up the trunk before the leaves unfurl. My beekeeping friend Stewart showed me how to drill a small hole with a hand drill in the birch trunk and insert tubing which carries the sap into a large food grade plastic container. Stewart’s a retired gamekeeper with a lot of country skills up his sleeve, and he makes birch wine from his collections. I just wanted to drink the sap neat this time.

A refreshing glass of birch sap.

It’s really exciting to see how quickly the sap runs, and how every day there are several litres to collect. The sap needs to be used within around three days, or frozen at once, as it deteriorates quite rapidly otherwise and quickly grows mould. It is refreshing to drink and it tastes like a rich mineral water, which of course it is. Birch sap contains life sustaining substances such as:  calcium, magnesium, potassium, fructose, glucose, fruit acids, amino acids, vitamin C, phosphorous, zinc, sodium, iron, and malic, phosphoric, succinic and citric acids.

Birch sap also contains sugars manufactured in the leaves during the growing season by a process called photosynthesis which also traps energy from the sun. The leaves are green in summer because they contain tiny bodies of protoplasm called chloroplasts which are coloured green by a pigment called chlorophyll. In a pretty amazing chemical reaction, carbon dioxide and water taken in by the leaves from the atmosphere are acted on, with the assistance of sunlight, by chloroplasts which convert them into sugars that travel down the tree’s vascular system to be stored in the roots. As a by-product of photosynthesis, life- sustaining oxygen is given off into the atmosphere which is why trees are so beneficial environmentally.

Let’s look a little more closely at the fluid transport system within trees. This consists of specialised tissues called phloem and xylem. The phloem carries sugary fluid from the crown and leaves down into the trunk, whilst the xylem carries nutrient- saturated water back up into the crown and leaves from the root system.  In the following photograph you may notice a thin dark ring in the middle of the trunk. This ring separates the very centre, containing non-vascular tissue, from the xylem which can be seen as a dark brown circle just under the knobbly bark, and the phloem lies between the xylem and this thin dark ring

You will notice that the xylem is quite thin and this is what we tap into when we drain off sap and so you will realise why you only need to drill approximately 1.5 inches to reach the sap. Between the thin dark circle and the xylem is the phloem which is a much larger area.

The vascular system of a felled willow tree. Photo by Keith Edkins.

A friend of mine in the USA taps sugar maple trees and boils down the sap to make a fine syrup. He owns a small woodland which he holds in a special woodland conservation trust to protect the trees and prevent building development. He knows a lot about managing trees for sap production and gave me some good advice on tapping my trees. A couple of spiles (spigots) arrived from the USA for me to try out next season.

Beelistener’s birch syrup, glass of sap and metal spile.

The photograph shows Canadian spiles which are inserted into the bore hole, and from which the sap runs into tubing, or a bucket. These spiles are only 4mm in diameter and cause less trauma to the tree than using a larger bore tube would because it is easier for the tree to repair a smaller hole. Current recommendations are to leave the hole unplugged once the sap has stopped running out of the tree because the tree will heal itself, whereas some tissue damage is caused when holes are plugged with cork or wooden bungs, due to a build-up of sap which is never reabsorbed back into the xylem. The spiles have a hook to hang a bucket on.

If you would like to give it a go here is what you need to do: firstly, select a suitable tree that has a diameter larger than eight inches and that has not been exposed to pesticides or other toxic substances. It is essential not to use trees with any fungi growing on them as these may be dead or dying trees. You should only tap healthy trees.

When you tap trees depends on which part of the country you live in due to the fact that you need to start 2-3 weeks before the leaves appear, and the further north you go in the UK the later this will be. I started mine on April 9th and stopped on 23rd April but each year will vary slightly.

The drill bit must small enough, 7/16 inch or 5/16 inch, to correspond to the size of spile being used, or food grade plastic tubing can be used instead of a spile. The drill bit needs to be sharp, spotlessly clean and soaked in alcohol before tapping. Select a spot about 3-4 feet off the ground on the tree trunk that is in the shade as much as possible and drill 1.5 inches into the bark at a slightly upward angle to promote downward flow of the sap. The drilled wood should be clear and white and if you notice brown shavings then that tree is best avoided because it may be dead or dying. Once you have cleared away the shavings you can then gently tap in the spile, or push in the plastic tubing to give a tight fit, but not so tight as to split wood around the hole. The sap will typically run for 14-21 days.

Some trees may produce a gallon of sap a day so have a plan before you start. Birch syrup is highly sought after by gourmets as a base for glazes and dressings for food like salmon and pork because it is subtly savoury and different from maple syrup which is higher in sugars. The flavour of birch syrup is distinctive with a hint of caramel. However, it is harder to make than maple syrup and requires much more sap because it takes around 100-150 litres of birch sap to make one litre of syrup. I boiled 8 litres birch sap in a jelly/jam-making pan to produce only 200 ml syrup (see photograph) but I was very pleased with it, though the professionals might say that it is a bit dark. A large shallow pan is best because it will take longer with a deeper one and the syrup darkens if boiled for too long. Birch sap is quite acidic so it is important not to use aluminium or cast- iron pans.

The sap needs to be brought to a fast rolling boil in order to evaporate the water as quickly as possible and it still takes a long time, producing lots of steam in the kitchen. I made mine in the same day but some people make batches of syrup that are concentrated, but not quite ready, and then put them all together at the end of the season to finish them off. You know it is ready when the syrup sugar content measures 66-67 % brix on a refractometer. Or, you can estimate by testing the thickness of the syrup, and noticing if steam has stopped coming off which will indicate that the water has evaporated. Bear in mind that hot liquid will always be runny so allow test sample to cool.

I gave away a lot of the sap that first season, but I froze several litres to enjoy throughout the year as a refreshing drink especially when plagued by winter colds. In future, I plan to use a smaller diameter hole and tubing. I’ll also store more sap in my freezer for enjoying later.  Perhaps you might be inspired to add another skill to your repertoire and tap your birch trees for soft drinks or wine making.

4 thoughts on “Birch Sap Drinks.”

  1. I’ll tell you a short story. I like Birch wine and our local Dobbies sells it. As a treat I opened a bottle and watched the Grand National. I should have paid more attention. The winning horse was Silver Birch. No, sadly I didn’t have a cheeky bet on it. 😊

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