保持水分

Complete the event The plants that were previously damaged to purge their corruption will not have a full health bar, and can be regenerated by pouring water on them. Grab the Water Jar next to Narcisse. Fill the jar at the nearby fountain (the fountain also has a Water icon on top of it, indicating it can be used). Use the pouring skill when next to plants with a health bar that's not full. Do this action 10 times to receive the achievement.

You can tell when the plant has received water by its health bar increasing as well as the (happy plant noises) chat bubble.