The Mediterranean Sea 900 AD
Scurvy, the scourge of sailors for millennia. Vitamin C, the scourge of scurvy. As the master shrubbers knew, you can pack a lot of Vitamin C into a shrub, it doesn't take up much space, makes the water taste good. And whilst the science will not come to the fore until much later in maritime history, shrubs are a staple of many a seafaring vessel plying its trade across the waters of the Mediterrannean Sea, and will still be being consumed by sailors a millennium later.