I pitted mine. If you pit them, then freeze them and after a couple of days they will be ready to make wine. You can ferment with the pits in, but some seeds tend to make the wines bitter. Don't know if plum seeds will, but I would guess they mite. I also would wash them, then pit. Save the juice as you pit them and pitch it in the must with the plums. Also, it is easier to remove the fruit after ferment if you put it in some kind of a ferment bag. The brew stores sell them, the big box stores or paint stores sell them as paint straining bags. Much easier to pull a bag out of the must rather than trying to rack around floating fruit. Good luck with it, Arne.
