ITIS list Artemesia dracunculoides as a synonym of A. dracunculus. With A. dracunculus 'Sativa', the name Sativa is capitalized and in single quotes which means it is a man made cultivar of A. dracunculus, not a subspecies. So just guessing here but I would say, Russian Tarragon is A. dracunculus with a synonym of A. dracunculoides. French Tarragon is a cultivar of A. dracunculus, thus A. dracunculus 'Sativa'.
