The young leaves are best left to dry slowly-almost to fermenting, but if you’re in a rush you can dry them in an oven but it won’t taste as good. 4-5 leaves/person minimum, it is a tea that I can’t recommend highly enough for its refreshing flavour. Remember to pick leaves well away from busy roads to avoid traffic contaminants. Somewhere I read that the Romans used the leaves to staunch wounds when they were on their ‘campaigns’ but I’ve never been able to trace that source.
Pregnant, nursing women and children under 2 should not use blackberry leaves.