Right, the mold occurs naturally as the moisture leaves the gourds; those 2 gourds that were just sitting there looking like nice winter squash have finally started to "give it up" (their moisture, that is) since being left out and getting a bit of freezing and thawing. I'm not sure what would happen if I left them outside for the entire winter up here in the north -- from the articles that I've read, that isn't advised; but I might leave a couple out next year and see what happens.