Birch sap, birch water or birch juice is the sap directly tapped from birch trees, Betula pubescens (white birch), Betula pendula (silver birch), Betula lenta, Betula papyrifera, and Betula fontinalis. Birch sap may be consumed both fresh and naturally fermented. When fresh, it is a clear and uncoloured liquid, often slightly sweet with a slightly silky texture. After two to three days, the sap starts fermenting and the taste becomes more acidic. Birch sap is a traditional beverage in boreal and hemiboreal regions of the Northern Hemisphere as well as parts of northern China. Harvest Birch sap is collected only at the break of winter and spring when the sap moves intensively. Birch sap collection is done by drilling a hole into the tree trunk and leading the sap into a container via some conduit (a tube or simply a thin twig); the sap will flow along it because of the surface tension. The wound is then plugged to minimise infection. Birch sap has to be collected in early spring before any green leaves have appeared, as in late spring it becomes bitter. The collection period is only about a month per year. No published evidence exists to quantify the long-term impacts of sap harvest on birch tree and birch forest health, or birch timber quality. However, the wounds caused by tapping birches consistently lead to dark staining in the wood. In one study, infection and wood decay had spread from more than half of old tapping holes. In comparison to maples, birch trees are considered far less tolerant to the wounds caused by tapping, so more conservative harvesting practises have been recommended by trade bodies such as the Alaska Birch Syrupmakers Association. Traditional regions Ancient Balts, Slavs and Finns regarded birch as one of their most sacred trees and made a traditional beverage from it. Slavic regions In Slavic regions the sap is known as birch juice as in Russia (), Belarus (, Byarozavik), Bulgaria (Bulgarian: брезов сок, romanized: brezov sok), Poland (), Slovakia (), Ukraine (). Baltic regions Estonia (), Finland (), Latvia (), Lithuania (). Other regions France, Scotland, Norway, Sweden () and elsewhere in Northern Europe as well as parts of northern China and both Hokkaido and Aomori as parts of northern Japan. It is also widely used among the Pennsylvania Dutch, both as a traditional beverage in its own right, and particularly as a key