What’s the halacha concerning terumos and maasros for herbs such as rosemary, parsley, coriander, mint, etc.? What about herbs used for making tea, such as mint, scented geranium, etc.

There is a distinction between herbs that are eaten as is and herbs that are used for flavoring. Those who eat parsley, coriander and mint as is should separate terumos and maasros with a bracha. However rosemary and scented geranium are not eaten as is, rather they’re just for flavoring and are removed from the dish prior to its being served, and therefore one does not have to separate terumos and maasros from them. In cases where there is a safeik, such as mint (where one does not normally eat it as is), one should separate terumos and maasros without a bracha.