in March / April
choose a tree which has cca 20-30 cm diameter at 1m height
at 1m height, drill a cca 2cm-5cm hole with 0.5 cm diameter
insert a drinking straw or a glass tube
collect max 2-3 liters per tree
enclose the drill hole with earth/soil and ash (otherwise the tree could "bleed to death")
for a chosen tree, do not apply more often than once in 2 years
Birch provides four good things: she illuminates (used for torches); she strangles cries (birch tar used for creeking wheels); she heals the sick and she purifies (birch canes in sauna).