I am newly moved to the Pacific Northwest with a load of various houseplants grown in my native Minnesota. Upon watering my plants (some new and acquired here) two weeks ago, for the first time I noticed a uniform white film of mildew on the exterior of all the terra cotta pots.

I have never had any such problems before, either with mildew of the soil or foliage. The plants remain perfectly healthy, but even after wiping the mold off the pots and allowing them to dry out, the mold is beginning to regrow.

Has anyone else experienced similar problems with mold/mildew on the exterior of terra cotta pots? Could it be a question of air humidity or overwatering, or is it something more sinister?

Any suggested remedies?

Thanks for your suggestions!