Fields of Mistria players should get in the habit of foraging as they explore the land. Anything foraged can be sold or donated to the museum for Renown. However, there are certain items that you'll need for side quests. Blueberries aren't as common as wildberries, but you'll need to gather some in order to complete the "Request for Blueberries." It's one of Fields of Mistria's simpler quests, so it's a good idea to get it done as soon as it becomes available.