David Livingston wrote:Mint is tough stuff I owner if the issues drainage in the or lack of it . I would replace the soil with something better draining .
I was under the impression that odium is French for mildew
David
Mildew in french is mildiou (same prononciation and yes i'm french Canadian).
Found in Wikipedia that powdery mildew is one kind of oidium so at the end it is the same...
I don't think the draining is the issue since it is in pot and dry out quickly. All of my other plants did not had powdery mildew (except one contamination of the mint right next to it and was treated with ease).
This type of variery of mint even grow on lakes and river shores.