When to sow Oriental Poppy Seeds - Zone 6

[GardenGeisha]

I'm in Salt Lake City, Zone 5/6ish. This past summer someone gave me some Oriental poppy seeds harvested from their plants. I would say this was in June. I planted some at the time but saved some back. Do you think it would be better to plant them now or wait until the spring? Do you think they'd tend to rot over the winter in the ground? When would you plant them in the spring? Don't they need some cold-stratification?

Thanks in advance,

Clare