For historical context, I'd like to provide some information. This event takes place sometime around the year 180 BP, or in the common calendar, about 210 after the First comet. The quest referred to by Prior Claude is the quest to establish Ántouïst presence in the south of Martoise. Upon finding the Valley, dubbed the Lavender Valley for obvious reasons, they set up a small monastery at the very southern end, tucked away in the mountains. The existence of the monastery allowed southern Martois citizens living in towns and villages to travel just a few days, as opposed to the weeks it would normally have taken before, to come and ask for guidance from the monks. And after a few centuries, the region would become settled by many--first miners, then traders, and eventually growing into what is now the city of Havrelée.
Unfortunately, occupation of the valley caused the lavender population in the region to dwindle. But the monastery, adopting the flower as a holy symbol, kept the species alive and spread them across the Dántaine. It is no longer known whether or not lavenders grew elsewhere before the intervention of humans, but legend has it that all lavenders in the Dántaine are descendants of flowers grown in the Valley, possibly even in the gardens of the monastery alone. Lavender is now a rather hot commodity in Martoise.