There are plenty of online recipe for adding essential oils to syrup batches - I'm going with 15 drops lemongrass and 15 drops spearmint for a 1 gallon quantity of syrup. BUTTT, I also made the syrup ahead, because I wanted it to have thyme tea in it (thymol, the easy way), and then froze it, so it's sort of soft and squishy in the freezer now. Didn't put the essential oils into it because they will evaporate, and lose their efficacy, so will do that once thawed and ready to be put on the hive. Whenever that is!