It would be nice if there was a quest in the quest rotation to seal the haze, if it's not sealed, to nudge players in that direction. My partner and I didn't realize it was an option - we made it all the way to finding the burrs in the flower pot on the shed porch, wondered where to find more, and ended up Googling it. There's not really any obvious hints that sealing the Haze is how you get burr weeds, or even any hints that it's possible.