What are white spots on dead prairie dock leaf - Ask Extension
This question is from last fall... In the Eloise Butler Wildflower garden I came across a dead prairie dock and was struck by its leaves, which are ev...
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What are white spots on dead prairie dock leaf #947534
Asked October 22, 2026, 6:16 PM EDT
This question is from last fall... In the Eloise Butler Wildflower garden I came across a dead prairie dock and was struck by its leaves, which are evenly covered with white spots. I'd like to understand more -- I'm guessing its a fungus, but what kind? Mildew? Why is it so evenly distributed -- is it growing in the leaf's stomata? I'm curious to understand more, and think its quite beautifu... Thank you!
I've attached a picture I took of the leaf in question.
Hennepin County Minnesota
Expert Response
It could be powdery mildew, but the pattern is so regular I think it is part of the leaf structure. Leaves of prairie dock showing the same pattern have been noted by others. This suggests that it could be part of the leaf structure. It would be something to investigate with a microscope.
