I harvested a bunch of coriander seeds last year for cooking purposes. I've been adding them to soups and stock. However, I noticed the remaining ones had gone mouldy (there was this fine brown-grey dust when I poured some onto a chopping board) in the jar so I tossed them into the ground. This winter (I'm in the southern hemisphere), I saw the seeds have sprouted. Now, I wonder if what I thought were mouldy coriander seeds were actually perfectly safe to eat. Has anyone encountered this before? Is there a way to prevent them getting "mouldy"?