Rowan berries are not poisonous, but can cause stomach upset. This liqueur is safe to drink!
I put the rowan berries in the freezer for a day, just the fruit, no stems or anything like that. Harvest time was October because I picked them before the first frost.
Put the frozen rowan berries with the other ingredients in a container and store in the dark for 6 - 8 weeks.
Pass the liqueur through a sieve, filtering is not necessary.