Every fall now for several years I have dug some of the rosemary in my
garden, potted in growing medium, and brought it indoors.

Invariably, soon after I have brought it in, the leaves start to get covered
with powdery mildew.

I can usually keep it alive by washing it frequently but it doesn't thrive.

It has been suggested that I should open a window every day and let it have
fresh air but this is impractical as the temperature gets well below
frreezing.

Could it be that I am keeping it too wet? When I pot it I soak it well to
set the roots into the potting medium.

Any suggestions?

Brian