This is a description how to collect birch sap from your own birch as a beverage for a family of four.
During the summer, the birch tree stores nourishment for the next period of growth in its roots. The following spring, this nourishment rises as sap through the trunk up to the branches.
The birch tree emits sap only for a short period of time (about four weeks) during spring. That period starts when the snow has melted away and the day-temperature reaches some degrees above freezing point. The rise of the sap stops immediately when the tree comes into leaf.
During sap-rising, a big old birch can give 15-20 liters per day, but this requires a tapping-hole of 5 cm diameter and 10 cm depth. The birch will endure such treatment only once, maybe twice in its lifetime.